The Surprising Factors that Impact Your Blood Sugar

In addition to what and when you eat, many other factors can impact your glucose.  Elevated glucose due to these other factors can be a signal from your body that it needs extra care and attention until things return to normal.

As you’ll learn in this article:

  • Poor sleep, fatigue, and pain tend to raise our glucose levels, while
  • Exercise and the monthly female cycle can raise or lower your glucose, depending on the context. 

In this article, let’s delve into the 854,633 glucose values from 8,880 people who have used our Data-Driven Fasting app to understand the things that impact your glucose and how you can use these insights to optimise your blood sugar levels and metabolic health.

The Data

In our Data-Driven Fasting Challenge, Optimisers use their glucose, guided by the DDF app, to make informed choices about what and when they eat.  But when they log their glucose in the DDF app, they also have the option to highlight an associated ‘event’. 

The DDF app then calculates a temporarily elevated trigger that they can use for the next 24 hours, which means they can still eat when hungry despite the non-food factors affecting their glucose. 

To date, we have collected more than a hundred thousand blood glucose values with an associated ‘event,’ giving us some fascinating insights into how much these factors impact our blood glucose. 

Eager to learn more about the other factors that impact your glucose and what to do about it? 

Read on!

Things that Raise Your Glucose

The table below shows the factors that tend to raise our blood glucose.  The ‘increase’ columns show how much they raise glucose (in mg/dL and mmol/L), while the number column shows how many times they’ve been logged. 


While poor sleep and stress are the most reported events, pain tends to have the largest impact on blood glucose. 

All these factors drive a stress response in your body.  Your body responds with increased cortisol, adrenaline, and glucagon, which drives your liver to pump more stored glucose into your blood until the stress is over. 

All these factors disrupt homeostasis and make us crave more energy-dense foods to ensure we have enough fuel to survive the current emergency, especially if it goes on for a long time.  Your body will also hoard your stored fat until the emergency ends and things are calmer. 

You probably know you’re stressed, tired, exhausted or in pain.  But elevated glucose, which your recent food intake can’t explain, is a useful wake-up call to ensure we pay attention and take action to give our body the rest it needs. 

We’ll touch on these factors in more detail later, but let’s double-click on two of the factors that can raise or lower your glucose:

  • exercise, and
  • the monthly hormonal cycle (for females). 


The first interesting thing to note is that:

  • People who logged an exercise event (n = 3,562) had an average glucose of 100 mg/dL (5.6 mmol/L).
  • Those who didn’t log an exercise event (n = 2,955) had an average glucose level of 103 mg/dL (5.7 mmol/L). 

As we might expect, people who exercise are more likely to be metabolically healthy, with lower glucose levels.

On average, glucose rises by 3.5 mg/dL (0.2 mmol/L) after exercise.  While the average response in glucose might seem small, we see a wide range of responses, with some people experiencing a rise of more than 70 mg/dL above their average glucose.  Others see their glucose fall more than 60 mg/dL after exercise.   

As highlighted in the image below, intense exercise beyond what your body is accustomed to can raise your glucose.  In contrast, lower-intensity exercise tends to lower glucose.  If the exercise is more intense than normal for you, you’ll see a larger change in glucose from your normal. 

Exercise can Lower Your Glucose

In Data-Driven Fasting, we suggest people use light exercise as a proactive ‘hack’ to reduce their blood glucose before or after they eat.  If your glucose is above your current trigger, going for a short walk can be a fantastic way to encourage your muscles to use the excess glucose in your bloodstream and bring your glucose back below your trigger.   

Going for a walk is also an underrated stress reliever.  Getting out in the sun, particularly earlier in the day, will also help you sleep better at night.

Intense Exercise Can Raise Your Glucose

Meanwhile, intense exercise beyond what your body is accustomed to can raise your glucose. 

Sensing the emergency, your liver dumps stored glucose (glycogen) into your bloodstream to fuel the exercise.  In times gone by, this emergency response would have ensured we had the fuel to run away from a tiger.  Today, we pay for gym memberships and intentionally stress our bodies to ensure they adapt and become stronger rather than weaker due to inactivity.   

Because you’re using up the stored energy in your body, the rise in glucose is not something to be feared.  When you exercise, your body soaks up the glucose in your blood without requiring insulin (i.e. non-insulin mediated glucose uptake).

After an intense workout, rather than waiting until they reach their premeal blood glucose trigger, we encourage our Optimisers to eat a robust meal when they first feel hungry.  Waiting too long can lead to intense hunger as your body tries to refill the glycogen in your muscles, often leading to poor food choices.  

If your glucose rises or falls a lot after exercise, it might be better to dial back the intensity a little until your body adapts, especially if it makes you extremely hungry afterwards.  It’s better to start small, be consistent, and build up slowly rather than hitting the wall and falling off the wagon. 

Fuelling for Exercise

Many people wonder if they should work out before or after they eat. 

Is fasted exercise better?  Will it help me burn more fat? 

The answer depends on the context. 

Eating something before exercise would be smart if you’re feeling hungry and weak and your glucose is lower than normal.  You’ll also need to be well-fuelled if you’re hoping to sprint faster or lift heavier.  But most people have plenty of energy available to fuel their normal workout, especially earlier in the day due to the dawn phenomenon

Should I Eat Before I Work Out?

If you do fuel up before you work out, it’s also smart to ensure you don’t over-fuel with fast-acting carbs just before you start your activity.  This can cause a bump in insulin, which leads to a crash in glucose (aka bonking due to reactive hypoglycaemia) when you start your activity. 

To avoid this, you want to ensure your pre-workout food doesn’t cause a rise in glucose more than 30 mg/dL (1.6 mmol/L).   It’s ideal to fill up a couple of hours before your activity to give your body time to digest and store the energy and avoid the glucose crash when you start your workout.    

Intra-Workout Fuelling

If your glucose is above your current trigger, you probably don’t need to eat unless the activity lasts more than an hour.  Just be ready to eat a robust meal when you return home.   You can test your glucose and fuel and eat accordingly after the workout.  If glucose is significantly below your trigger, add some fast-digesting carbs to bring glucose back up. 

But if your workout lasts more than an hour, testing your glucose when you stop for a break can be helpful.  If glucose is well below your trigger, adding a high-carb snack will help to ensure you have plenty of glucose supply to your muscles.  

People on a lower-carb diet, mostly fuelled with fat, often find that their glucose doesn’t fall much because they have lower insulin levels and a steady stream of energy from their fat stores, meaning they don’t have to use up their stored glucose as quickly. 

A continuous glucose meter can be helpful during long-duration activity to measure your glucose in real-time and ensure you are fuelling adequately.  However, remember that CGMs measure interstitial glucose around your muscles, not the glucose in your blood, which is closest to the fuel supply from your stomach and liver.  So, you may see a much lower glucose reading on your CGM than your glucometer. 

The bottom line is for longer activities where you need performance:

  • you want to keep your glucose above your current glucose trigger to ensure you have enough fuel and
  • below the upper limit (i.e. 30 mg/dL or 1.6 mmol/L above your current trigger) to ensure insulin stays low and you avoid bonking.  

The Female Monthly Hormone Cycle

Next, let’s double-click on the data to see what we can learn about the female monthly hormonal cycle and its impact on glucose. 

Post Menopausal Women Have High Blood Glucose Levels

The first thing to note is that the 893 women who logged a menses event had lower average glucose (97 mg/dL or 5.4 mmol/L) than the 4189 women who didn’t log a menses event (102 mg/dL or 5.7 mmol/L). 

This makes sense, given that we know that after menopause, the decrease in estrogen often leads to an increase in body fat.  In our programs, post-menopausal women have great success when dialling up their protein percentage to ensure they get the protein they need within their decreased energy requirements.  For more details on this, see:

Premenstrual Change in Glucose and Insulin

On average, women who logged a menses event recorded glucose values 1.2 mg/dL (0.1 mmol/L) higher than their normal.  However, there is a wide variation in response, as shown in the chart below. 

Some women see a rise of more than 16 mg/dL (0.8 mmol/L), while others see it fall.  While the ‘menses’ trigger in the DDF App is intended to be used in the days leading up to menses, the drops in glucose may be due to the menses event used during menses itself. 

After ovulation and before menses, the female body acts as if it may be pregnant, increasing insulin resistance to grow and store energy to support a possible new foetus.  The rise and fall in insulin and glucose follow the progesterone levels shown in the diagram below. 

To illustrate, the chart below shows my wife Monica’s insulin variation over 38 cycles.  Her closed-loop insulin pump increases insulin to keep her blood glucose levels in the target range. 

Notice how insulin levels peak between days 16 and 25 of her cycle.  This also coincides with increased hunger, fluid retention and water weight gain.  But once her body decides it’s not pregnant, insulin levels drop, and the water weight and appetite follow. 

The 2016 study, Changes in Macronutrient, Micronutrient, and Food Group Intakes Throughout the Menstrual Cycle in Healthy, Pre-Menopausal Women, showed that average energy intake increases by about 70 calories per day in the late luteal phase. 

The practical implication is that a pre-menopausal woman can be more aggressive with her weight loss approach in the first half of the cycle, focusing on leaner protein, higher nutrient density and a little less energy from fat and carbohydrates in the first half of the cycle, particularly once menses finishes. 

Meanwhile, in the second half of the cycle, she can allow a little more food and energy from fat and carbs while prioritising adequate protein and nutrients.  For more details, see Navigating Blood Sugar, Insulin and Menstrual Cycle: A Comprehensive Guide.

Pain & Sickness

As noted above, pain tends to cause the highest rise in glucose of all the events, with an average rise of 4.6 mg/dL (0.4 mmol/L) above normal levels. 

Pain and sickness are signals from your body that you need to rest and give it some attention.  Elevated blood glucose levels can tell you are getting sick and need to rest and pay attention to nourish your body.  Medications like steroids or vaccinations can elevate your blood glucose for a week. 

Some people become hungrier when they’re sick, and others will lose their appetite.  We suggest taking a break from tracking your glucose and trying to lose weight during this time.  You can always pick up where you left off when things return to normal. 


Your body also sees poor sleep as a stressor, pumping out more glucose to help you cope and survive the current threat.  Your appetite for energy-dense, nutrient-poor foods will also increase. 

Sleep is the #1 bio-hack you can employ to maximise your health and productivity the next day, so make it a priority. 

If you see your glucose elevated due to poor sleep, there are some simple things to do to improve your sleep hygiene if you’re not doing them already:

  • Have a consistent wind-down routine (e.g., finish work at X pm, eat dinner with family, go to bed to read at Y pm, and sleep by Z pm).  
  • Use an eye mask.
  • Limit stimulating social media before bed and turn off electronic devices and screens at least an hour before bed. 
  • Take some sneaky naps during the day if you’re feeling drowsy.
  • Stop caffeine after noon.
  • Go for a walk and see some sun (ideally with your dog and/or a family member) earlier in the day.

If you struggle to feel refreshed in the morning, you could talk to your doctor about a sleep test to rule out sleep apnoea, which is particularly prevalent in older men with some level of obesity.


It’s hard to avoid stress, but there are many things you can do to manage it.   You may already have your favourite things that help you forget your worries and relax, like meditation, exercise, socialising, reading a good book or watching a good movie to escape. 

Many people find meditation helpful; some find it a bit woo-woo.  But simple long exhale breathing exercises can help take your mind off the worries that stimulate your parasympathetic nervous system (rest and digest) and calm your sympathetic nervous system (fight or flight). 

Focusing on your breath helps to take your mind off the worries of the outside world.  One option is to ‘pay attention to your breath’ as you breathe.  Another is to count as you breathe out.  If you want to pay attention to your body,  you can count your heartbeats as you breathe out (e.g. breathe out for five heartbeats and then aim for six heartbeats next time).  It’s hard to worry about the day’s stress when you’re focusing on your heartbeats. 

Another option is timed breathing cycles.  The screenshot from the iBreathe app shows a timed breathing cycle.  Once you can easily cope with a certain exhale time, using the principles of progressive overload, you can increase it to make it a little harder so you’re spending more time with less oxygen, which also upregulates nitric oxide, enabling your red blood cells to use oxygen more efficiently later, which also has beneficial effects on insulin sensitivity.  Once I’ve completed a short breathing exercise, I can more easily focus on what I want to do rather than being distracted by the noise of what everyone else wants me to do. 

To learn more about this, check out James Nestor’s Breath: The New Science of a Lost Art or anything by Patrick McKeown.


Beyond food, many factors, including poor sleep, stress, pain, sickness and fatigue, can raise our glucose levels.  Left unchecked, these factors can lead to increased appetite and poorer food choices, leading to elevated glucose levels.   In addition to guiding what and when to eat, your glucose can be a useful indicator that you need to give your body a little extra TLC. 

We also looked at insulin and glucose fluctuations around the female monthly hormonal cycle and how we can navigate it with more energy in the second half of the cycle but with more focus on nutrient density and less energy in the first half after the completion of menses. 

Similar to how we can use our glucose to guide our fuelling for weight loss, we can also use glucose to guide our fuelling for exercise. 

Recognising the things that cause stress and impact our glucose further empowers us with knowledge.  It guides us in making informed lifestyle choices.  By paying attention to these often-overlooked factors, we can better manage our glucose levels by enhancing our overall well-being and vitality.