Reactive Hypoglycemia: Avoiding the Blood Sugar Crash

Do you often feel a sudden dip in energy, irritable moods, or extreme hunger soon after eating? If so, you might be experiencing reactive hypoglycemia, a condition where blood sugar levels plummet following a meal. Despite adhering to general dietary guidelines, some individuals find themselves caught in this vexing cycle.

This article sheds light on reactive hypoglycemia, helping you understand its causes, symptoms, and how you can tailor your diet to prevent those draining blood sugar crashes. Whether you’re a wellness enthusiast or someone battling post-meal lethargy, this guide is poised to equip you with valuable knowledge and actionable strategies to manage your blood sugar levels, paving the way towards a healthier, more energetic you.

What Is Reactive Hypoglycemia?

  • To unpack the medical terminology:
  • hypoglycemia is a fancy word for low blood sugar, while  
  • reactive hypoglycemia refers to low blood sugar shortly after a meal.

Many people who are lean and metabolically healthy have lower blood glucose. As a general rule, if you feel OK, you are OK.  There’s usually no need to worry about lower blood glucose if you didn’t take medications (like injected insulin, metformin, berberine etc.) to lower your blood glucose. 

Reactive hypoglycemia is low blood glucose levels soon after a meal accompanied by one or more adverse symptoms of low blood sugar, which we’ll discuss below. 

‘Low’ is a relative term when it comes to blood sugar.  If your blood sugars typically run high, your low may be ‘high’ for someone else.  You’ll feel shabby and hungrier than usual when YOUR blood glucose falls below what is typical for you, especially after falling from a great height.   

For context, the chart below shows the premeal blood glucose values distribution in our Data Driven-Fasting Challenges.  As you can see, not many people see blood glucose below 70 mg/dL before they eat.

premeal glucose

Can Hypoglycemia be Controlled with Diet?

In this article, we’ll dive into the nuances of reactive hypoglycemia and the various possible causes. 

But if you’re experiencing low blood glucose after eating, the step is to review what you’re eating when you experience symptoms of reactive hypoglycaemia. You can then modify your diet accordingly. 

As shown in the image below, blood glucose usually rises after we eat.  Your body then responds with insulin to slow the release of stored energy from your liver until you’ve used up the excess fuel in your blood. This causes your blood glucose to return to normal levels a few hours after you eat.

reactive hypoglycemia leads to hunger and energy crashes

You’ve probably heard the saying, ‘What goes up, must come down’.  This is also true for your blood glucose.  The higher your glucose rise, the larger the insulin response.  This can lead to a rapid drop and a nasty crash in your blood glucose a few hours later when your glucose falls below what your body is comfortable with.

It’s often not the low blood glucose itself that feels bad, but rather the rapid drop in blood glucose after it rises way above your normal level.

If you test your glucose before and after you eat and find this is happening, first, it’s worth taking note of which meals cause your glucose to rise the most. 

In our various programs, we suggest people review what they are eating and look to dial back refined carbohydrates if their blood glucose rises more than 30 mg/dL (1.6 mmol/L) after meals. 

For reference, the chart below shows the distribution of glucose rise after eating in our Data-Driven Fasting Challenges:

  • Towards the left, we see that some people see a slight glucose drop after eating.
  • Towards the right, you can see that some people see a rise of more than 50 mg/dL.
  • Meanwhile, the average rise after eating is a healthy 16 mg/dL (0.9 mg/dL).
glucose rise after eating

The more your glucose rises after you eat, the greater the risk that you will experience reactive hypoglycemia. However, once you limit the rise in glucose after you eat, you will also limit the insulin released after the meal, hence the nasty crash afterwards.  

To help you, we have created a range of optimised food lists you can grab here.  Start with the low carb and blood sugar list initially to stabilise your blood sugar and then transition to the low carb and fat loss list if your blood glucose still rises by more than 30 mg/dL after eating and you also want to lose some body fat or reverse your insulin resistance. 

We also have a range of NutriBooster recipe books that are an excellent place for people to start.    

What Does Reactive Hypoglycemia Feel Like?

Symptoms of reactive hypoglycemia are no different than those of hypoglycemia aside from their time of onset (i.e., soon after meals).  They include, but are not limited to:

  • anxiety,
  • double or blurry vision,
  • racing heart,
  • confusion,
  • dizziness,
  • moodiness and mood swings,
  • irritability,
  • nervousness,
  • flushing,
  • tremors,
  • sweet cravings,
  • rhinitis,
  • panic attacks,
  • numbness and cold in extremities,
  • confusion,
  • irrationality,
  • hot flashes,
  • bad temper,
  • mood swings,
  • trouble talking,
  • disorientation,
  • hangriness,
  • the need to sleep or ‘crashing’,
  • insomnia,
  • headache,
  • fatigue,
  • hunger,
  • light-headedness,
  • sweating,
  • poor concentration,
  • shakiness,
  • trouble sleeping,
  • feeling wired,
  • feeling faint,
  • extreme tiredness,
  • weakness,
  • paleness,
  • mouth tingling,
  • heart palpitations, and
  • nausea.

These symptoms of reactive hypoglycemia are all relieved when someone eats.  So, it’s no wonder that constantly feeling this way can lead us to eat more than we need to to avoid feeling any of these symptoms. 

Symptoms and low blood glucose must both be present; symptoms related to hypoglycemia can mirror other conditions.  Reactive hypoglycemia is not considered to present without symptoms accompanying low blood glucose (i.e., you cannot just have low blood glucose). 

To understand if you may be experiencing reactive hypoglycemia, you can test your blood glucose before eating and each hour afterwards for four to five hours.  If you are experiencing glucose levels well below your blood glucose before you ate, along with adverse symptoms, there may be cause for concern, especially if your glucose rises by more than 30 mg/dL (1.6 mmol/L) after eating. 

The chart below shows the hourly glucose chart from our DDF app.

  • To minimise the risk of reactive glycemia, we encourage Optimisers to identify meals that raise their glucose above their upper limit line (i.e. 30 mg/dL or 1.6 mmol/L above their current trigger.
  • We also encourage them to eat when they are hungry because their glucose drops below their current trigger.

By doing this, they avoid foods that raise their glucose the most, thus preventing rapid falls in glucose and ensuring that they avoid symptoms of reactive hypoglycemia by eating before their glucose gets too low while still losing weight.

Once they learn to keep their glucose in the normal healthy range, hunger no longer feels like an emergency, and they regain control of their healthy appetite signals and give their body the fuel it needs when it needs it.

Different Types of Reactive Hypoglycemia

With the basics out of the way, let’s dive into the details of reactive hypoglycemia and the various other factors that contribute to it.

There are two different mechanisms of action behind reactive hypoglycemia.  There are also several types of reactive hypoglycemia, depending on their origin, which we will discuss below.  But as you’ll see, they all relate to an excessive insulin response after eating.

Let’s start with the two mechanisms of action.  Reactive hypoglycemia can occur because:

  1. There is an abnormally high rise in blood glucose not long after eating, leading to a higher-than-average quantity of insulin that’s secreted.  Here, blood glucose rises a lot after eating, insulin is secreted, tissues rapidly take up glucose for storage or use, and your plasma blood glucose drops (aka crash).
  2. Someone’s insulin production is still prominent, but their plasma blood glucose and insulin are already low.  Subsequently, their plasma glucose level eventually falls much lower than baseline.  This is known as hysteresis.

As we’ve discussed, reactive hypoglycemia refers to the occurrence of post-meal low blood sugar (i.e., postprandial hypoglycemia) two to five hours after someone’s last meal.  However, there are several types based on the timeframe the hypoglycemia occurs, including:

  • Alimentary reactive hypoglycemia, which occurs at 90 to 120 minutes post-meal.  This type of reactive hypoglycemia is most common in people with digestive dysfunction, like those with congenital mutations in genes that regulate insulin and blood sugar and others who have undergone gastrectomy.  Essentially, hormones—like glucagon-like peptide-1 (GLP1)—are dysregulated.
  • Idiopathic reactive hypoglycemia, which is characterised by hypoglycemia at 180 minutes post-meal.  Causes of hypoglycemia in this timeframe are often a result of a complex combination of factors.  For example, most patients have delayed insulin secretion in conjunction with falling blood glucose levels.  Some potential causes include a defective glucagon response, with glucagon being the antagonistic hormone of insulin that liberates stored energy; an increased insulin response from insulin resistance or GLP1; renal glycosuria, or a condition where the kidneys remove too much sugar from the blood; or high insulin sensitivity, which can occur as a result of hereditary factors or from things within our control like calorie deficit, exercise, and more, which we will talk about later on.
  • Late-reactive hypoglycemia, which occurs around 240-300 minutes post-meal.  While late reactive hypoglycemia and Type-2 Diabetes, prediabetes, and metabolic syndrome are not mutually exclusive, people with this form of reactive hypoglycemia are more susceptible to diabetes than the above two.  This form of reactive hypoglycemia is categorised by hyperglycaemia that’s initially exaggerated during a glucose tolerance test after someone’s initial mealtime.  Plasma insulin remains high after nutrients have disappeared, causing blood glucose to crash.

Why Does Reactive Hypoglycemia Occur?

To understand why reactive hypoglycemia occurs, we must understand the physiology of blood sugar regulation.  Insulin release is categorised into two distinct phases:

  • In the first phase, a short spike of insulin is released immediately alongside the consumption of a meal.  This phase lasts approximately ten to fifteen minutes.
  • The second phase follows the first phase.  In contrast to the first phase, the second phase is characterised by a gradual increase and plateau after around 120-180 minutes (2-3 hours) following a meal.
first and second phase insulin response

Interestingly, many people with early-onset glucose dysregulation at risk for Type-2 Diabetes do not demonstrate the first phase, or it is very irregular.  In fact, this is the earliest indication of defective beta cells (i.e., cells that produce insulin) in people who often develop T2D.  

Because the first phase is absent or inadequate, the second phase is late to release and often excessive as the body tries to compensate.  When insulin levels increase to such high levels, insulin receptors on muscle and fat cells are stimulated, prompting increased glucose uptake in a rapid timeframe.  Hence, blood glucose levels fall quickly. 

If you’ve been following the Optimising Nutrition blog, you may have heard me talk about Dr Bernstein and the Law of Small Numbers.  It can be hard for people with Type 1 Diabetes to correct large glucose spikes and get them under control with injected insulin. 

But the same principle still applies if you’re not injecting insulin.   It can be challenging for your body to produce the right amount of insulin to control things efficiently and accurately, especially if you are experiencing some degree of insulin resistance and consuming more carbohydrates than your body can easily handle.

Some people believe that the insulin response to carbs causes your body to release insulin, making you fat (i.e., the carbohydrate-insulin hypothesis of obesity).  But this is not really how it works. However, a large rise in glucose due to an excessive intake of refined carbohydrates leads to a crash in blood glucose shortly after that leads to extreme hunger and overeating can cause you to gain weight. 

For more details, see:

What Causes Reactive Hypoglycemia in People with Diabetes?

Let’s look at reactive hypoglycemia in people with diabetes a bit more deeply.

Medication and Exogenous Insulin

If you’re someone who has Type-1 Diabetes or insulin or drug-dependent Type-2 Diabetes and you’re reading this, there’s a chance you may have already started working on your metabolic health.  If this is the case and you’re still suffering from reactive hypoglycemia, it might be worthwhile checking if you’re:

  • Taking too much insulin,
  • Taking too high a dose of a medication like metformin and (or)
  • Taking too much of a glucose-lowering herb or supplement could directly (intentionally using it to lower BG) or indirectly (taking it for something else) result in reduced blood glucose and reactive hypoglycemia.  Some common BG-lowering supps include but are not limited to berberine, artichoke extract, cinnamon, alpha-lipoic acid, bitter melon, ginseng, fenugreek, and milk thistle.

While this may seem obvious, your body may become more efficient at managing your blood glucose sooner than anticipated.  As the body begins to unload some of the energy it has on board, and you begin to slip below your Personal Fat Threshold, your pancreas may regain function, and you may be less dependent on medications.  You can talk with your doctor to see if this might be the case for you.

Poor Glucose Control

Aside from the more obvious causes of reactive hypoglycemia, it could occur from poor glucose control and insulin resistance.  This often happens after prolonged periods of metabolic stress, like calorie excess, too little movement, nutrient deficiency, and overconsumption of fat-and-carb combo foods. 

Over time, eating and moving this way will push someone above their Personal Fat Threshold, or their body’s bio-individual limit of energy it can handle before developing metabolic syndrome. 

Instead of thinking of insulin as an anabolic hormone, I like to think of it as an anti-catabolic hormone.  In other words, insulin serves as the brake pedal that halts the flow of stored energy from your liver glycogen, body fat, and tissues into your bloodstream. 

As you get fatter and fatter and exceed your Personal Fat Threshold by more and more, your body will have to produce more and more insulin to hold it back in storage.  Unfortunately, over time, the body cannot keep up with its demands, and beta cells of the pancreas begin to burn out.  As a result, the first wave of insulin is not produced nor released, so blood sugars climb until the over-compensatory second wave is released.

As a result, someone has low blood sugar in the ‘late-reactive hypoglycemia’ stage timeframe four to six hours after consuming a sizable meal.

What Causes Reactive Hypoglycemia in Non-Diabetics?

Reactive hypoglycemia in non-diabetics is a bit different.

Because your stress hormones are so tightly intertwined with insulin and glucagon, I wanted to take a minute to explain their regulation for background on a large chunk of this next section.

Adrenals, Cortisol, and Chronic Stress

Your peripheral nervous system (CNS) can be divided into two sections:

  • Your autonomic nervous system regulates your involuntary bodily processes, like breathing rate, digestion, movement of food through your GI tract (peristalsis), blood pressure, heart rate, and sexual arousal.
  • Your somatic nervous system helps you move and regulate voluntary processes in your body.

We will be focusing on your autonomic nervous system.  This ‘category’ of your nervous system can further be broken down into:

  • Your parasympathetic nervous system (PNS) is sometimes referred to as a ‘rest-and-digest’ state.  Here, your heart rate, blood pressure, and pulse are normalised, and your body can heal, digest, absorb nutrients, sleep, and mount a regulated immune response.  It is estimated that we evolved to spend around 80% of our lives in the rest-and-digest state.  However, our modern lifestyle sometimes challenges this!
  • Your sympathetic nervous system (SNS), or your ‘fight-or-flight’ response, responds to stressful stimuli (perceived stress, anyway).  When activated, your blood pressure, heart rate, and respiratory rate all increase to boost oxygen supply to the rest of your body.  Circulation thus increases, and blood flow is diverted from your centre and towards your distal limbs so you can escape danger.  Digestion, peristalsis, immune system function, and healing are all put on hold when the SNS is engaged, and hormones related to SNS activation are released.  It is estimated that we only evolved to spend around 20% of our lives in fight-or-flight.

So, how does this relate to reactive hypoglycemia?

During fight-or-flight, stress hormones like epinephrine and norepinephrine are released over the short term and cortisol over the long term.  This can prompt glucagon to release your glycogen reserves to get you out of danger and may even reduce the amount of insulin produced.  Together, this can change the amount of energy available for your system.

When your lizard (primitive) brain and SNS are activated from perceived stress, or stress your body thinks is a direct threat to your life—like running from a predator or a warring tribe, scavenging for food during a period of food scarcity, or crawling back over a cliffside after nearly falling over—your body’s primary goal is to supply your tissues with energy to get you the h*** out of danger! 

But as smart as your body is, it can’t differentiate from what’s really going on, whether it be a strict deadline at work or school, financial stress, relationship problems, excessive exercise, a self-mediated calorie deficit to lose weight, or something else.  As a result, that stress and those stress hormones can alter your blood sugar by instigating reactive hypoglycemia (amongst other things).

To show you a few real-world examples of how perceived stress and fight-or-flight activation might be affecting you, we broke it down a bit further.


Whether you’re running for fun or from a predator, lifting weights at the gym for stress relief or lifting yourself over a cliff, or swimming recreationally or from alligators, any exercise that increases your heart rate is considered a stressor. 

The release of stress hormones triggers glucagon, which liberates stored energy from glycogen and body fat to power your activity.  Stress hormones also decrease insulin sensitivity.  Together, these influences will raise blood sugar acutely while you’re in the act.  This fuels your workout and gives your body some power to get it out of danger. 

Not long after, your blood sugar will likely drop as energy-dependent tissues like muscle remain insulin-sensitive and still try and absorb any residual energy that’s floating around your bloodstream.  Despite your workout ending, they still require fuel to recover and replete some of that energy they just burned up.

Now, if you eat immediately after your workout when stress hormones are still high and you’re insulin sensitive, your blood glucose might fall not long after a meal as that energy you just consumed goes right into your cells.  Additionally, not eating enough, not eating enough carbs, and even overeating protein—as it can lower BG on its own—can further exacerbate the magnitude of reactive hypoglycemia you might experience after a meal.

If this sounds like the case for you, you can try delaying your meal time about an hour after your workout.  This gives your body time to get out of a stressed state and for cortisol levels to fall.  Depending on the exercise duration, you might try adding a pre-workout snack or drink.  You may do better with something during your workout if it is an endurance event or heavy output (i.e., heavyweight, high reps, cardio involvement).

Chronically Stressed State

We all deal with some degree of psychological stress (i.e., mental and emotional) from time to time.  Whether it be relationships with friends, a significant other, family, or colleagues, school or work deadlines, or traumatic events, it’s, unfortunately, a constant.  However, the magnitude of how it affects you differs from person to person.

Aside from mental stressors, someone might be under chronic stress if they are dealing with a chronic illness, like autoimmunity, cancer, or even Type-2 Diabetes.  In addition, chronic infections like Lyme disease and environmental stressors like toxic mould can often contribute, as they keep your body’s immune system hypervigilant. 

Finally, chronic stress—or the long-term activation of the sympathetic nervous system and release of stress hormones like cortisol—can even stem from lack of sleep, over-exercising, under-eating (which we’ll get into in a minute), excess toxin exposure, or long-term drug use.  Chronic stress might even be from a combination of all of the following.  Here, you can picture your stress limits as a bucket where a little bit of each eventually causes it to overtop.

Epinephrine and norepinephrine are released acutely in stressful situations to engage the fight-or-flight response ASAP.  But as that stress is active from seconds and minutes to hours, days, and weeks, your body begins releasing cortisol.

Like if you were working out, cortisol triggers the release of glucagon, which allows your body to liberate its energy stores to fuel you out of ‘danger’.  This inhibits insulin sensitivity and alters energy uptake to your tissues.  Over time, this can lead to erratic blood sugar and poor glucose control.

Additionally, it takes a ton of resources for your body to produce cortisol; your adrenals are in charge of this life-dependent task.  As time goes on and on and on, and the stress does not resolve, your adrenals can become stressed.  Like the pancreas of someone with diabetes, your adrenals—two small glands atop your kidneys—might begin to wear out over time.  This results in a condition known as adrenal fatigue.

Modern medicine is only beginning to recognise the effects of adrenal fatigue.  However, it tends to take on two stages:

  1. A hyperadrenic state, or ‘adrenal alarm’ phase, often occurs early in the condition.  Here, the adrenals are more prone to overproducing cortisol and producing cortisol at the wrong times of the day.  This is not to be confused with Cushing’s syndrome.
  2. A hypoadrenic state, or ‘adrenal exhaustion phase’.  Here, the adrenals begin to fatigue and cannot keep up with the cortisol output their body demands.  Subsequently, someone is more prone to excess fatigue, low blood pressure, low heart rate, low body temperature, poor blood glucose control, postural orthostatic hypotension (POTS), and poor fluid balance because of the many roles cortisol plays in all of these bodily processes.  A hypodermic state is not to be confused with Addison’s disease.

Ultimately, what is important here is that chronic cortisol release alters blood glucose control over time.  And your body continues to produce more and more cortisol as you become more and more stressed. 

In a hyperadrenergic state, your body will be more prone to hypoglycaemic episodes unless you’re eating regularly and replacing the energy your body is burning through.  Additionally, you will be more inclined to erratic blood sugar as cortisol impairs insulin sensitivity.

If the stress continues and you move into a hypodermic state, your body may be unable to produce adequate cortisol to trigger glucagon release.  As a result, your body might not even have the stamina to release stored energy in the form of glycogen or body fat when you’ve gone for even short periods between meals, leading to a hypoglycaemic episode.

To add to it—and I know this is a lot—but low blood glucose is a stressor on the body.  So, if you’re falling into a hypoglycaemic state several times a day, you might exacerbate your problem without knowing it!  It becomes a vicious cycle.

To begin healing your body from adrenal fatigue or even supporting it through chronic stress, it’s essential to eat regularly.  To cater even more accurately to your body’s needs and learn to give your body what it needs when it needs it, you might even consider partaking in one of our Data-Driven Fasting Challenges, where we guide you to use your blood glucose to fine-tune when and what to eat.

While our Data-Driven Fasting Challenges are designed to help people lose weight using their glucose as a fuel gauge, the core takeaway from the challenge is to teach you how to use your blood glucose as a fuel gauge and determine when it’s best to refuel. 

This allows you to get in touch with your unique symptoms so you know when to eat to keep your body out of a stressed state.  Our DDF app also has a maintenance mode designed to help people eat regularly to maintain their weight after the challenges that you might like to try. 

In terms of stress, another condition known as adrenergic postprandial syndrome also can occur.  Here, someone gets hypoglycemia symptoms, but their blood glucose is normal.  Their symptoms are more conclusive with the condition.

Inadequate Calorie Intake Over the Long-Term

Now, using the section on a chronically stressed state, we can use what we know to understand what occurs when we’re in a caloric deficit—whether intentionally or unintentionally—for prolonged periods.  

Chronic calorie inadequacy is a stressor on the body.   Your body perceives starvation and food scarcity if it continues for a prolonged period.  Similar to what we explained above regarding chronic stress, blood glucose control may diminish after some time eating at such a substantial deficit. 

Eating at a caloric deficit often increases your insulin sensitivity.  Thus, it may also be behind your reactive hypoglycemia as your body becomes so hungry for energy when it’s not readily available that it’s absorbed readily into tissues when you finally eat again.  So if you’re consuming minimal amounts of food at each meal, your body might quite literally be burning through your food immediately.

Additionally, your body could still be producing more insulin than it needs.  If you’re eating inadequate-sized meals, your body may still be releasing too much insulin, which can drop your blood glucose not long after eating.  In combination with the point above, the effects could compound.

Excessive Fasting

Fasting is when someone abstains from food for a set period.  Most of us naturally fast overnight when we don’t eat because we’re sleeping.  However, some people adhere to set fasting windows, like 14, 16, 18, 20, or even 24 hours (OMAD), which can push someone to ignore their innate hunger cues.  These methods, of course, have pros and cons.    

Fasting for longer than your body is comfortable with is a stressor.  It also often results in a calorie deficit—at least in the beginning.  As stress wears on the body from inadequate energy intake, many people end up regaining the weight they lost because they end up bingeing as soon as they let themselves eat again.  This is because they let their blood sugar fall well below their average, which creates uncontrollable hunger.

When you go to refeed, insulin sensitivity is extremely high, and tissues absorb the energy readily.  As a result, your glucose might fall shortly after.  If your calories are far below your calories out, the effects of this scenario compound.  While this is fine in the short term, your body can perceive it as active starvation and scarcity the longer it continues.  Because of the stress it exhibits on your body, your adrenals and pancreas may lose the ability to regulate BG over time.

Inadequate Carbohydrates

Low-carb and even ‘zero-carb’ diets are popular for managing metabolic syndrome and inflammatory conditions like autoimmunity and complex and chronic illnesses (i.e., Lyme disease). 

If you’re new here, I’m a big-time advocate for using a low-carb diet to manage blood glucose and conditions like T1D and T2D.  But in some instances, it might be doing you more harm than good, depending on your state of health, and I want to talk about why.

It’s essential to remember that the body works as a system; rarely does dysfunction in one part of the body not affect another.  In terms of long-term adrenal imbalance—from chronic stress stemming from diseases and conditions like diabetes, autoimmunity, mast cell activation syndrome (MCAS), chronic mould exposure, Lyme, and even inflammation—adrenal hormones other than cortisol begin to fall out of balance. 

As we mentioned earlier, low blood sugar is a stressor on the body.  Low-carb diets often lower baseline blood glucose, especially if they are used for longer and longer periods, and the person eating low-carb isn’t overconsuming energy.  If someone already tends to lower blood glucose levels and (or) if they have been in a chronic state of stress for some time, a lower-carb diet can become highly stressful on the body, especially with long-term use. 

People’s bodies under long-term stress chronically produce cortisol, which makes tissues increasingly resistant to insulin.  As a result, eating doesn’t necessarily get them out of a low, nor does it relieve the stress that has resulted from hypoglycemia. 

Someone who is more active or struggles to eat adequate calories may have an even harder time with hypoglycemia eating a low-carb diet as the food they’re eating makes it difficult to get blood glucose above baseline.  Hormones, especially in menstruating women, can also make this more challenging depending on where you are in your menstrual cycle.

Your hormonal system, commonly called the endocrine system, is not limited to sex hormones and cortisol.  In fact, it refers to the unique interaction of around 50 hormones (signalling molecules) that tell other organs, cells, and tissues near and far what to do and how to do their jobs. 

A few of these other organ systems that interact with glucagon, insulin, and cortisol include the thyroid, reproductive system, adrenals, kidneys, liver, heart, and brain.  With regard to the brain, the hypothalamus and the pituitary glands are arguably the most critical and are often termed the ‘master regulators’ of the body.  

The hypothalamus, pituitary, and adrenals interact so readily that this chain is often referred to as the ‘hypothalamus-pituitary-adrenal axis’, or HPA axis for short.  Hence, when one of these organ systems falls out of whack—like the adrenals when you go low-carb, and your body can’t handle it—the whole system can take a hit.

So, what does this have to do with low-carb diets?

Well, when you’re consistently low-carb for an extended period and your blood glucose is constantly dipping below its normal because you’ve been in a chronic state of stress for too long, other organs feel the effects.  A few examples of how these effects can transfer into different organ systems include:

Lowered thyroid output, as hormones like Thyroid Stimulating Hormone (TSH), become imbalanced from long-term stress on the hypothalamus-pituitary-adrenal (HPA) axis.  TSH is a hormone released by the pituitary gland, and pituitary function can be altered and suppressed during periods of prolonged stress.  Additionally, there are arguments as to whether or not long-term low-carb diets negatively affect the production and conversion of thyroid hormones like T4 and T3.  However, the sex of the person using the diet definitely plays a role, as the female hormone system and menstrual cycle are often affected more negatively than males.  Additionally, someone who is more stressed eating low-carb may not see as good of results as someone who is less stressed on low-carb.

Blood pressure and circulation changes, as chronic cortisol and blood sugar imbalances can affect how well our bodies hold onto minerals.  Eating a very low-carb diet can make it challenging to consume adequate minerals like potassium, calcium, sodium, and magnesium unless you’re targeting nutrient-dense whole foods like leafy greens, seeds, and dairy products, as we advise in our Macros Masterclass

Additionally, insulin is critical for mineral retention.  This is why low-carb diets are known as diuretics; eating a minimally insulinogenic diet often prompts us to pee out a lot of our minerals, increasing our demand for electrolytes.  Aside from insulin, adrenal hormones like aldosterone and anti-diuretic hormone (ADH) also play a role in mineral and fluid retention.  Because we require these minerals to maintain blood pressure and thus circulation, adrenal imbalances and chronically low blood glucose can contribute to other conditions related to adrenal fatigue like postural orthostatic tachycardia syndrome (POTS), postural orthostatic hypotension, hypotension, brain fog, fatigue, and dizziness.

Imbalanced sex hormones.  As we mentioned above, chronic stress from hypoglycaemia can affect the entire HPA axis.  Because the hypothalamus and pituitary are involved in the function of other organ systems like the reproductive system, long-term low blood glucose can have delirious effects on some of the other bodily functions these glands regulate.  For example, follicular stimulating hormone (FSH) and luteinising hormone (LH) are hormones that regulate a female’s menstrual cycle.   They are also released by the pituitary gland.  If the HPA axis becomes dysregulated or its dysfunction is exacerbated by a low-carb diet, the release of other dependent hormones like estrogen, progesterone, and testosterone can be affected.  Additionally, cortisol steal—which we mentioned earlier—can occur, dysregulating the balance between your sex hormones.

While low-carb diets can help someone get control of erratic BG highs and lows, it’s critical to evaluate your situation and context before determining if it’s right for you.  If you’ve been on a low-carb diet for some time but are really struggling with chronically low blood glucose, you might strongly consider bringing some carbs back into the mix.

In our Macros Masterclass, we guide Optimisers, using their blood glucose to dial back their carbohydrate intake to the point that they typically see a rise after eating less than 30 mg/dL (1.6 mmol/L).  If your glucose rises by more than this, you’re consuming more carbohydrates than your body needs.  But if it’s below this, you don’t need to worry about reducing carbohydrates further. 

You Changed Routines Too Quickly

Are you one to go 0-100?  Changing up your routine too quickly might also prompt reactive hypoglycemia.

The human body is what it is because of adaptation, and it becomes accustomed to a routine with which you slowly shape it.  So, if you ate a low-protein, fat-and-carb-combo-diet (i.e., standard western diet) and were relatively sedentary in 2022 and you abruptly decided to #GoKeto and hit the gym five times a week on 1 January 2023, your body might still be adhering to its old schedule.

In other words, your body might struggle to utilise the low-glycemic energy (i.e., high-fat, high-protein) energy you’re suddenly relying on, and it may have a more challenging time accessing your body fat for fuel during activity. 

Protein is critical for muscle protein synthesis, and it’s the most thermogenic macronutrient.  However, it is rather difficult to convert into usable energy—especially in comparison to carbohydrates.  As a result, your body might have to adjust to relying on gluconeogenesis and fatty acid oxidation.

In our Macros Masterclasses and Micros Masterclasses, we recommend reviewing their current diet and then tweaking it in the direction you want.  Once you find your minimum effective dose or the minimum amount of change that allows you to lose an average of between 0.5-1.0% per week, you can hold at that dose until the changes slow.  Not only does this allow your body to adapt, but it also allows you to enjoy your wins and keep your sanity!

Excessive Alcohol

Drinking alcohol is known to drop blood glucose.  Yes, you heard me right!  And many studies have shown this, but not with a positive connotation.  Interestingly, many alcoholics have low blood glucose.  However, that is not an excuse to pour an extra glass of wine!

Many studies show this lowering of glucose might occur because it impairs the liver from releasing glucose into the blood while you’re burning off the energy from the alcohol.  Drinking on an empty stomach makes this even more difficult, which is why binge drinkers and heavy drinkers who usually drink on an empty stomach are more likely to experience low blood glucose.  As you can imagine, people who have already been diagnosed with diabetes are even more at risk.

Low blood sugar in and around meals from alcohol consumption also lowers inhibition, which may prompt you to make poorer food choices.  These poor food choices might then contribute to the onset of T2D and metabolic syndrome, especially if you consume them more often than not.  If you regularly drink alcohol with your meals, this might be something to consider, too!

Vitamin and Mineral Deficiencies

Many nutrients contribute to blood sugar regulation.  We’ve included some of the most critical ones below.

  • Chromium is significantly involved in insulin binding and insulin sensitivity, and people with diabetes tend to burn through it rather quickly, given its role in the human body.  Thus, deficiency can have a role, and new research shows this.
  • Magnesium plays a role in moving glucose into the cell and works as a second messenger to insulin.  Thus, low Mg could contribute to reactive hypoglycaemia.  It’s also been linked to reactive hypoglycemia directly, as magnesium deficiency (in rats) resulted in heightened glucose uptake to the muscle, which decreased blood glucose levels.
  • Low potassium has been associated with low blood sugar.  It has also been shown to have a role in the metabolisation of glucose.
  • Certain trace elements like cobalt, boron, chromium, copper, sulphur, iodine, zinc and molybdenum enhance insulin action by activating insulin receptor sites.

Nutrient inadequacy can contribute to dysregulated insulin release and poor glycemic control.

If you’re interested in upping your micronutrient game, you might check out our four-week Micros Masterclass, which walks Optimisers through filling in their nutrient gaps to get the most out of ALL of their calories.

Additionally, we’ve put together several hundred recipes over the past few years that could be some of the most nutrient-dense recipes on the market.  What’s even better is that we also put together a suite of NutriBooster recipe books, which are tailored to individual preferences and goals (i.e., dairy-free, egg-free, vegan and vegetarian, meat, etc.) to take a lot of the effort out of nutrient density.

Menstrual Cycle

As discussed in What to Eat for Each Phase of Your Menstrual Cycle, hormones play a massive role in glucose tolerance and blood sugar stability.  Thus, where you are in your cycle can considerably affect glucose and insulin regularity.

During the first half of your cycle—the follicular phase—blood glucose remains relatively stable, and carbs are tolerated best.  However, if you’re in the second half of your cycle—your luteal phase—blood sugar can get progressively more irregular leading up to your physical bleed, especially if you already have pre-existing hormonal imbalances. 


Considering hormonal fluctuations in your menstrual cycle are known to fluctuate your blood sugar, it might not be surprising that reactive hypoglycemia during pregnancy is not uncommon.

Pregnancy can cause secondary hypoglycaemia and sometimes diabetes because of insulin’s effects in pregnancy.  This—and the modern diet—are why many women develop diabetes during pregnancy.

Although pregnancy and food aversions are also not uncommon, it’s crucial to make an effort to consume high-satiety protein, fibre, and some healthy fats throughout your pregnancy.  Not only will this give you a stable source of energy to fuel you and your baby, but it will also give you the nutrients you need to grow them and have a healthy baby!

Fever and Illness

When the body is fighting an infection, your metabolic rate increases substantially.  Similar to a generator’s fuel requirements if it is running on high vs low output (greater and lesser fuel demand), your body has to increase its energy demands to raise body temperature to generate a fever and fight off pathogens.  Thus, you can burn through your blood glucose and glycogen stores quickly.

When you go to eat again, your insulin sensitivity is high.  Thus, energy from food quickly makes it into your tissues, which might leave your sugars low not long after.  Additionally, reactive hypoglycemia can be exasperated if you’re only consuming higher-carb foods—which isn’t uncommon when you’re sick, as nothing sounds good.

Although you might not have much of an appetite when you’re sick, eating can be helpful.  In fact, you might even feel worse because your blood sugar is also low!  Plus, eating a good bit of protein gives your body the resources it needs to make antibodies and other immune-boosting nutrients.

The intersection of sex hormones like estrogen, progesterone, testosterone, and other hormones like insulin is just starting to catch the public eye and the interest of science.  However, sex hormones and insulin contribute to an extensive system known as the endocrine system, which readily interacts.  Thus, many conditions related to hormone imbalance are connected to blood sugar dysfunction.

Sex hormones and thyroid hormones require sex hormone-binding globulin (SHBG) to be excreted and metabolised.  Insulin is known to decrease SHBG synthesis and use some of it, which can contribute to irregularly high amounts of estrogens and androgens floating around in a man or woman’s system.

On another note, the body favours the synthesis of cortisol over other hormones like progesterone and estrogen.  Thus, when we are under enormous amounts of stress—from mental stress, illness, pain, injury, poor glucose control, fasting, or whatever—high amounts of cortisol are produced.

As mentioned earlier, sex hormones are synthesised down the same pathway as cortisol, but cortisol has priority.  This occurrence is known as ‘cortisol steal’, and it usually causes a decrease in progesterone relative to estrogen to occur because cortisol is made from progesterone.  Subsequently, estrogens outnumber progesterone.  Additionally, many synthetic estrogens make it into our systems nowadays from plastics, toxic food, water, and even beauty care products.  Thus, we can see estrogen-dominant conditions like endometriosis and androgen-dominant conditions like PCOS.

While you may be experiencing reactive hypoglycaemia, you may find your ‘root cause’ is really hormonal imbalance.  However, the body is highly efficient, and unless you have some sort of tumour, it usually doesn’t randomly ‘malfunction’ and produce odd amounts of hormones.  Thus, excess stress, poor diet, and toxin exposure might actually underly and contribute to your reactive hypoglycemia.

Is Reactive Hypoglycaemia Dangerous?

Reactive hypoglycaemia can be dangerous for some people whose blood sugar levels dip to an extreme.  

These people may see confusion, changes in behaviour, slurred speech, clumsy movements, blurry or double vision, loss of consciousness, seizures, coma, and even death.  However, most of the more severe symptoms are often linked to excessive use of medications like insulin and metformin or extreme underlying pathologies. 

If you suffer from any of these conditions and have no root cause, you may try taking your blood sugar using a simple glucometer around the onset of some symptoms.  This may help you pinpoint what the root cause is, and it might also help you get in tune with why you feel a certain way (i.e., are you anxious because your blood sugar is low?).

On another note, someone with severe adrenal insufficiency can experience some of the more severe side effects.  This is because of the relationship between cortisol, hypoadrenalism, and conditions like Addison’s disease and hypoglycemia.  Thus, reactive hypoglycaemia can be dangerous if your sugars get too low for too long or if you have another pre-existing condition that is aggravated by it (i.e., adrenal dysfunction).

Is Reactive Hypoglycaemia a Sign of Diabetes?

There can be multiple root causes behind reactive hypoglycemia, but it can be a sign of insulin resistance or pre-diabetes.  

As we explained earlier, the time of onset of your reactive hypoglycemia is often an indication of the root cause.  If yours falls into the late reactive hypoglycaemia classification—or reactive hypoglycemia that’s onset approximately 240 to 300 minutes after your meal—this type of reactive hypoglycemia most often aligns with diabetes and insulin resistance.

Once again, reactive hypoglycaemia is often a symptom of dysfunction elsewhere.  It’s essential to remember that reactive hypoglycemia is not always mutually exclusive with diabetes, as there can be multiple root causes.  Nonetheless, you should talk to your doctor about reactive hypoglycaemia—especially late reactive hypoglycaemia that occurs 4 to 5 hours after your last meal—as it may indicate early blood sugar dysregulation issues.

Does Reactive Hypoglycaemia Cause Weight Gain?

Reactive hypoglycaemia does not directly cause weight gain.  However, many people gain weight because they fall victim to their appetite and give in to cravings as soon as their blood sugars plummet.  Eating more food more frequently leads to weight gain over time.  Therefore, reactive hypoglycaemia and weight gain can go hand in hand.

Because adrenal dysfunction is also associated with thyroid and sex hormone imbalances, poor adrenal output can also play a role in conditions like hypothyroidism or hypoadrenalism.  The thyroid, adrenals, and sex hormones (i.e., estrogen, progesterone, and testosterone) all influence one another tremendously. 

It’s important to note that sex hormones are synthesised down the same pathway as stress hormones (i.e., cortisol).  Because cortisol is essential for life, the body will prioritise its synthesis in times of need to keep you alive.  So, your body will make fewer sex hormones—which are considered pro-fat burning—to make more stress hormones—which are associated with body fat.  Additionally, chronic stress can also contribute to conditions related to hormonal imbalances, like polycystic ovarian syndrome (PCOS) and endometriosis.

The critical takeaway is that reactive hypoglycaemia is often a symptom that something else is out of balance, and whatever ‘that’ is could contribute to your reactive hypoglycaemia, weight gain, and a myriad of other symptoms (i.e., see the symptom list above!).

Does Reactive Hypoglycaemia Go Away?

Reactive hypoglycaemia can resolve if you get to the root cause; this is why it’s so important to determine what yours is!

If you have diabetes or prediabetes, you can work on dialling up your protein relative to your carbs in fat like we do in our Macros Masterclass.  This not only ensures satiety via nutrient density, but it additionally provides your body with stable energy. 

You can also check out our Data-Driven Fasting Challenges, which walk you through how to use your blood glucometer as a fuel gauge to determine when to refuel and what to refuel with.  Data-Driven Fasting guides you to lose weight by tapping into your fat stores when your glucose is just below what is normal for you while avoiding waiting so long that your glucose drops and you feel ravenous!

If you find that your reactive hypoglycemia stems from chronic stress, it’s critical to manage it and normalise the balance of your adrenals.  You can do this by eating meals more frequently as determined by our Data-Driven Fasting Challenges, eating adequate calories, and consuming ample electrolytes throughout the day.  You can use our free Macro Calculator to determine your ideal intake of calories and look at our ONIs to figure out the optimal amount of each core electrolyte (i.e., sodium, potassium, calcium, and magnesium).

Treatment for Reactive Hypoglycaemia: Is Reactive Hypoglycaemia Curable?

To manage reactive hypoglycemia, some people recommend eating small meals ‘every three to four hours’ consisting of ‘whole grains, fruits, vegetables, and lean proteins, and taking small doses of fruit juice, sugar, or glucose when blood sugar is low.

However, our work on the food insulin index shows that foods like whole grains have a relatively high insulin and blood glucose response, which could contribute to erratic spikes.  We recommend ratcheting down your carb intake if your blood glucose rises more than 30 mg/L (1.6 mmol/dL) after a meal.

Taking to these recommendations also doesn’t teach us what or how much of each to consume, nor does it often prioritise the most critical macronutrient for satiety and blood sugar stabilisation: protein. 

We recommend checking out our four-week Macros Masterclass to learn how to adequately build a plate for nutrient density, satiety, and blood sugar stabilisation. We recommend checking out our four-week Macros Masterclass.  Here, Optimisers learn how to dial up their fibre and protein while dialling back their carbs and fat to find the most optimal intake for their goals and preferences.

Similarly, snacking frequently and not eating substantial meals can cause minor spikes and falls, forcing you to eat more regularly.  On another note, eating too frequently as can interfere with digestion.  Our Data-Driven Fasting program can teach you how to use a simple blood glucose meter as a fuel gauge to determine when and what you should eat.  Once people find foods that provide greater long-term satiety, they can easily go longer between meals without being consumed with thoughts of what they are going to eat next.

Reactive hypoglycaemia is still highly manageable.  However, you must be diligent about how, what, and when you eat, and you must be willing to look at the root of your problem.   

What Can I Do to Manage Reactive Hypoglycaemia?

In many instances, a nutrient-poor, processed, standard Western diet and a stressful Western lifestyle often play a role in hypoglycaemia, hormonal imbalances, and adrenal dysfunction.  Switching to a nutrient-dense diet isn’t an overnight fix and requires diligence, hard work, and practice.  However, it is the best shot you have at reversing your condition and moving towards remission.

Make sure you’re eating whole, unprocessed, nutrient-dense foods that fit your goals and preferences.  By sticking to whole foods, you’ll eliminate many of your triggers right off the bat!  This means avoiding sugar from candy, baked goods, processed carbs (i.e., pasta, pizza), fruit juice, and even too much fruit.

Ensure you’re eating enough, but not too much energy.  Too many can make you fat, and too little can cause a stress response.   

Consume adequate to high amounts of protein, fibre, and fat at each meal.  If you are more active, you may need more carbs.  Like energy intake, you must find the ‘goldilocks’ dose of each macronutrient that works for your body and its day-to-day expenditure.

Protein is a satiating, blood sugar-stabilising macronutrient.  Dietary fat spikes blood sugar the least, and carbs elicit a significant blood glucose response in the short term.  If this sounds difficult to coordinate, you may enjoy our four-week Macros Masterclass.  Here, we walk our Optimisers through dialling up their protein while dialling back their carbs and fat.

If your hypoglycaemia is related to intense activity (exercise), excessive fasting, low carb, or undereating, you may consider adding in some carbohydrates.  If you have adrenal fatigue or hypothyroidism, this may be your root cause, especially if you’ve eaten too few carbs for a prolonged period.

While we’re on the topic of exercise, eating some carbs before or right after a workout might be worthwhile to replenish glycogen stores, especially if your blood sugar is low after working out.  You might also find you improve when you time your carbs.  Regardless of what your lifestyle looks like, avoid consuming carbs solo!  Always include protein. 

Whether you’re eating too much or too little, you may need to refine your eating times to ensure you’re giving your body what it needs when it needs it, which you can do with DDF.

Aside from energy and macronutrients, micronutrients are also critical.  Consume a nutrient-dense diet high in insulin-related nutrients like magnesium and chromium; you can work on filling all your micronutrient gaps using our four-week Micros Masterclass

If you find your adrenals are struggling, you may try Incorporating electrolytes.  You can do this in a cost-effective manner by using our electrolyte recipe here.  Salt and potassium are essential for the adrenal glands; both are often excreted at a higher rate during stress.  Try sipping on electrolytes throughout the day in every serving of water you consume, especially if you are low-carb!

Additionally, do not overconsume caffeine, alcohol, or stimulants.  All of them can potentially stress your adrenals and drop blood sugar.  If consumed consistently, your blood sugar may become erratic, and you may exacerbate your already-persistent cortisol imbalance (or you can create one).  If you find you are reliant on caffeine, you may want to scroll back up to the adrenal section!

If you’re someone who injects exogenous insulin for T1D or T2D or you take blood sugar-lowering medication, you may want to check how much of each you’re using, especially as you work towards Nutritional Optimisation.  If you’re becoming healthier metabolically, you might need less, and they may be dropping your BG unnecessarily!  In our programs, many people need to dial back their medication as they lose weight and find the energy to exercise more.

If you’re more sedentary, incorporating resistance training into your daily routine is pertinent as it improves insulin sensitivity, blood glucose control, the synthesis of pro-metabolic muscle tissues, and fat loss.  On the contrary, if you’re admittedly too active, you may consider decreasing the intensity and even frequency of your exercise to give your body a chance to recover or timing your meals to avoid glucose crashes around your workout.

Although we did not get into much detail on it—which I’d like to talk more about in a separate article—many conditions related to blood sugar dysregulation are rooted in a dysregulated circadian rhythm.  So, staying up super late, staring at blue light from your phone, tablet, watch, or computer until the night hours, and waking up long after the sun comes up could be throwing off your body’s natural schedule.  Try and be consistent.

Lastly, realise that things will not change overnight, and it will take consistency to regain your metabolic health, insulin sensitivity, and normal blood glucose control!

What Should I Eat If I Have Reactive Hypoglycaemia?

There is no one diet for reactive hypoglycaemia, but you can take a few steps listed here to begin to manage it and tailor what works best for you.

If your reactive hypoglycaemia stems from metabolic dysfunction and diabetes, getting adequate protein and nutrients is critical.  Not only do these micronutrients provide heaps of satiety, which will allow you to unload extra body fat and fall below your Personal Fat Threshold, but they will also give your body a steady source of energy that normalises blood sugars.

In addition to protein and nutrients, it is critical to minimise your intake of fat and carbs relative to protein and fibre.  The average population consumes around 12-19% of their total calories from protein, which is associated with the greatest calorie intake!  So, learn to prioritise protein and nutrients, just like we do in our Macros Masterclass. 

As shown in the chart below from our satiety analysis, we tend to eat much less as we dial up our protein %. Many people in our DDF Challenges use a protein-focused meal earlier in the day to drop their glucose while maximising satiety, especially if they are experiencing the dawn phenomenon, with higher glucose levels in the morning.

Our Data-Driven Fasting Challenges can help you determine your meal times using your blood glucose meter as a fuel gauge.

There is no one-size-fits-all reactive hypoglycaemia diet, nor is there one universal reactive hypoglycaemia treatment standard used by western medicine.  The origins of this condition differ for each of us!  So, we must stick to a bio-individual approach and make slow and steady changes while monitoring how our bodies respond.

How to Manage Reactive Hypoglycaemia with Lifestyle

Aside from diet, you can do a few other things to optimise your reactive hypoglycaemia, no matter the cause.

  1. Get at least eight hours of sleep every night, with no exceptions.  This does not include screen time hours!  Sleep is your body’s time to rejuvenate and heal.  Poor sleep is associated with poor glucose control, diabetes, many chronic diseases, and higher incidences of all-cause mortality.
  • Practice stress management.  This looks different for everyone, depending on their stressors!  For some, it’s distancing yourself from toxic relationships.  For others, it’s learning how to balance work life or school life with real life, finding hobbies you genuinely enjoy or practising stress management interventions like meditation, journaling, or breathwork.
  • Eliminate alcohol, tobacco, and other harmful substances from your lifestyle.  Aside from directly skewing blood glucose, these substances can also diminish judgement, create stress and inflammation, and alter your appetite and food discernment.
  • Practice habits to set your circadian rhythm.  This includes waking up and going to bed at the same time every day, taking a short walk or stepping outside and looking at the sun with your naked eye (no sunglasses) so your body knows it’s morning time, avoiding blue light exposure from devices past sundown, and building a schedule each day that’s somewhat habitual (i.e., waking up, going to bed, working out, and eating at similar times each day).

No matter the symptoms that accompany your reactive hypoglycaemia, the origins of why you have reactive hypoglycemia may differ from the person next to you.  While it is vital to manage reactive hypoglycemia, looking at it as a root cause instead of a symptom may keep you from progressing with your condition over the long term.


Home » Glucose & Insulin » Blood Sugar » Reactive Hypoglycemia: Avoiding the Blood Sugar Crash

2 thoughts on “Reactive Hypoglycemia: Avoiding the Blood Sugar Crash”

  1. I appreciate this information, and I have a question: do you have any nutrition advice for my condition–an endocrinologist diagnosed me with a non-working pituitary gland. I have low thyroid function, but was removed from all thyroid medicine due to its impact on my bones. Thank you.

Comments are closed.