Tracking your blood glucose with a continuous glucose monitor or a regular glucometer can be not only fascinating but also helpful in guiding when and what you eat.
However, while there are established criteria that diagnose metabolic syndrome, pre-diabetes, and Type 2 diabetes, there is sparse data on optimal metabolic health and the glucose levels someone should aim for to lose weight.
As more and more people are paying attention to their blood glucose, they often ask:
- ‘What is a good glucose number if they don’t have diabetes?’,
- ‘What is the best glucose level for weight loss?’, and
- ‘How low is too low when it comes to blood glucose?’
While a few people with diabetes have used Data-Driven Fasting to optimise their blood sugar levels, as you will see, most people are reasonably metabolically healthy and use their blood sugar levels to guide their weight loss.
By the end of this article, you will understand:
- The range of normal non-diabetic blood sugar;
- The most critical time to test your blood sugar;
- How to use your blood glucose monitor as a fuel gauge to guide when to eat for weight loss and to optimise your metabolic health.
- General Recommendations
- All Glucose Data
- Typical Pre-Meal Blood Glucose
- Typical Blood Glucose After Eating
- When Is My Glucose the Highest?
- How Much Should My Glucose Rise After I Eat?
- Normal Waking Glucose Range
- Why Is My Waking Glucose Higher on a Low-Carb Diet?
- Low-Fat Diet Glucose Pattern
- How Can I Make Better Food Choices Using My Blood Sugars?
- How Low Is Too Low When It Comes to Blood Glucose?
- What Is the Most Important Glucose Number to Manage?
- How to Optimise Your Blood Glucose
To set the scene, the table below shows the blood glucose values used to diagnose pre-diabetes and Type 2 diabetes. They include:
- fasting glucose (i.e., first thing in the morning before food),
- after-meal blood glucose (post-prandial), and
- Hb1Ac, or an estimate of your average glucose over three months.
Doctors often use these cut-offs to prescribe diabetes medications like metformin or insulin. However, we believe it’s ideal to address the root cause before you require medication.
If you’re reading this, you’re likely interested in optimising your metabolic health to avoid these medications that only manage symptoms of metabolic disease, like high blood sugar.
All Glucose Data
To help you understand what the range of healthy blood sugar looks like, the chart below illustrates the distribution of the 487,285 blood glucose values, both fasting and throughout the day, we’ve collected from our Data-Driven Fasting app in the past two years.
From this graph, we can see:
- The average blood glucose value is 99 mg/dL (5.5 mmol/L).
- To the far right, we see that only a few people have glucose values considered diabetic (i.e., greater than 200 mg/dL, 11.1 mmol/L).
- To the left, even fewer people have blood glucose levels below 60 mg/dL (3.3 mmol/L).
The chart below shows the same data in mmol/L for those outside the US. To convert mg/dL to mmol/L, simply divide by 18.
The table below summarises this data, showing:
- the 15th percentile, or the value that only 15% of values are below is 83 mg/dL (4.6 mmol/L),
- the 85th percentile, or the value that only 15% of values are above, is 113 mg/dL (6.3 mmol/L), and
- the estimated average HbA1c is 5.1%.
From this data, we can see that you’re likely metabolically healthy and reasonably lean if your average blood glucose is 83 mg/dL (4.6 mmol/L).
Interestingly, 83 mg/dL coincides with the ideal blood glucose value for adults recommended by one of my diabetes heroes, Dr Richard Bernstein. In this video, Dr B notes that children and pregnant women may have even lower glucose values.
He also mentions that most medical professionals don’t encourage people with diabetes to aim for the blood glucose targets that align with optimal health due to concerns about hypoglycaemia due to excess injected insulin. However, this is less of a concern when blood sugars are stabilised with a more diabetes-friendly diet.
If you’re not taking insulin to manage diabetes, it’s definitely ideal to aim for optimal blood glucose levels. If your blood glucose levels are high (e.g. waking glucose greater than 100 mg/dL or 5.6 mg/dL), you’ve exceeded your Personal Fat Threshold and need to lose some body fat to reduce your risk of the many diseases related to poor metabolic health.
The average HbA1c of 5.1% for our Data-Driven Fasting challengers is well below the cut-off for pre-diabetes (6.0%) and aligns with a lower risk of dying of any cause. As shown in the chart below, an HbA1c between 4.5 and 5.5% appears to have the lowest hazard ratio.
No matter where you fall in this range, you can still use your blood glucose to guide your weight loss, strive for more optimal metabolic health, and avoid the complications of Type 2 diabetes, as we do in our Data-Driven Fasting challenges.
In our Data-Driven Fasting Challenges, we walk our Optimisers through using their blood glucose data to guide when and what to eat. This allows them to lose weight and optimise their metabolic health to avoid using medications.
Most people tracking their glucose focus on their post-meal glucose or the glucose value after they eat. This is also known as the post-prandial glucose value.
However, as you will see, our analysis has shown that your pre-meal blood sugar levels deserve more attention if you want to lose weight and lower your blood glucose across the day.
This led us to develop Data-Driven Fasting, which uses your pre-meal glucose to guide you as to when to refuel and what you should eat.
Our Data-Driven Fasting app uses your average pre-meal glucose value over the first three to determine your pre-meal blood glucose trigger. After these three days, participants switch to ‘Hunger Training’, where they simply wait until their blood glucose level falls below your trigger before they eat.
The chart below shows the distribution of pre-meal glucose values (in mg/dL) logged in the Data-Driven Fasting Challenges.
The following chart illustrates the same data in mmol/L for those outside the US.
The table below summarises the analysis of 241,405 pre-meal blood glucose values. Here we can see:
- The average pre-meal glucose is 82 mg/dL (4.6 mmol/L).
- You’re likely metabolically healthy and fairly lean if your pre-meal blood glucose is towards the lower end of this range (i.e. close to 76 mg/dL or 4.2 mmol/L).
- However, if your pre-meal blood glucose is on the upper end of this range (i.e. closer to 88 mg/dL or 4.9 mmol/L or above), you may have some more work to optimise your metabolic health.
It’s worth noting that these glucose levels are typically from people chasing lower premeal glucose during our Data-Driven Fasting challenges. Normal glucose during weight maintenance may be a little higher. However, if your goal is weight loss and improved metabolic health, you can use these premeal numbers as a stretch target to work towards progressively.
Typical Blood Glucose After Eating
While post-prandial glucose isn’t our primary focus, we encourage people to check their post-prandial glucose to ensure they are not overfilling their glucose fuel tank with excessive amounts of processed carbs.
We recommend using a simple — and cost-effective — glucometer like the Contour Next One to get your reading. You can use the peak value if you already have or prefer a continuous glucose monitor (CGM).
The charts below show the analysis of 92,889 blood glucose values in mg/dL taken one to two hours after eating.
The chart below illustrates the same data in mmol/L for those outside the US.
The table below shows a summary of this data. Interestingly, the 85th percentile value (129 mg/dL) for our DDF Optimisers is below the cut-off for pre-diabetes (140 mg/dL).
When Is My Glucose the Highest?
Your peak glucose time can vary depending on what and how much you ate.
As represented by the ‘plant-based, low-fat’ (PBLF) green line in the chart below, your glucose might peak between 45 minutes to an hour after eating a low-fat, high-carb meal.
However, you may see your glucose trend lower and not peak until later if you eat a lower-carb, higher-fat meal. This is represented below by the animal-based low-carb (ABLC) line in red.
Carbohydrates cause blood sugar to rise and fall quickly. In contrast, dietary fat raises your blood sugar only slightly over time. But higher-fat meals tend to keep your blood sugar from dropping. So, combining the two — as many do with hyper-palatable, ultra-processed, fat-and-carb combo foods — will keep your blood sugar and insulin elevated for longer.
As we will discuss in the next section, when it comes to tracking blood glucose, the goal is not to achieve no variation and flatline glucose but rather to reduce the area under your glucose and insulin curves after you eat if your goal is to improve your metabolic health and lose weight.
For more info on the foods and meals that we suggest guide people consider using to achieve this, check out:
- The Most Nutrient-Dense Foods – Tailored to Your Goals and Preferences,
- Nutrient-Dense Meals and Recipes.
How Much Should My Glucose Rise After I Eat?
Because post-meal values are often used to diagnose diabetes, many people track this metric and focus on their glucose readings after they eat.
As a result, they try to minimise and manipulate the rise by:
- Avoiding carbs in the hopes of lowering blood sugar, reducing insulin, and therefore losing weight. This belief is rife in the keto community, and it’s caused many to gain weight over the long term. For more discussion, see Keto Lie #10: Stable Blood Sugars Will Lead to Fat Loss.
- Flatlining blood glucose levels, believing it will help them lose weight. We have seen this trend really take off recently with the rise in popularity of continuous glucose monitors (CGMs). See Glucose Revolution by Jessie Inchauspe (the Glucose Goddess): Review for more information.
- Eating excessive amounts of fat thinking it’s a ‘free food’ because it has the lowest insulin index value. At the end of the day, calories still count, and pure fat is pretty nutrient-poor and not satiating. For more on this topic, check out Keto Lie #11: You Should Eat Fat to Satiety to Lose Body Fat, Making Sense of the Food Insulin Index, and Keto Lie #12: If In Doubt, Keep Calm and Keto On!
The chart below shows the average rise in glucose after eating for 3,725 Data-Driven Fasting Challenge participants. We see only an average increase after eating of 16 mg/dL (0.9 mmol/L).
Note to the left of the chart many people see their blood glucose fall after eating. This often happens when people prioritise nutritious meals with a higher protein % or meals with a higher percentage of total calories from protein and less energy from fat and carbs. It’s a great ‘hack’ to bring blood glucose down earlier in the day when many people find their blood glucose is elevated.
An increase in waking blood sugar usually occurs due to something known as the Dawn Phenomenon. Here, stress hormones that help us wake up liberate stored energy, which registers on your meter. While some rise is typical, excessively high waking sugar and an increased BMI or body weight can indicate a dysregulated metabolism. For more detail, see Why Does My Blood Sugar Drop (or Rise) After Eating Protein?
All that said, the table below shows the analysis of the rise in glucose.
In our Data-Driven Fasting Challenges, we suggest that people consider cutting back on their carbohydrate intake or eating less of that particular food or meal if their glucose rises by more than 30 mg/L (1.6 mmol/L) after a meal. This indicates that they consumed more carbs than their bodies needed, and they ‘overfilled their glucose fuel tank’.
When managing your blood glucose levels across the day, it’s critical to remember that carbs are no worse — or better! — than fat. Instead, the combination of fat and carbs in conjunction with low protein keeps our blood sugar and insulin elevated for longer.
Normal Waking Glucose Range
While your waking glucose can be tricky to control, it’s potentially the most important to manage.
The charts below show the range of 124,858 waking glucose values that have been entered into the Data-Driven Fasting app over the past few years.
The table below summarises this data and shows an average waking glucose of 103 mg/dL (5.7 mmol/L). If your waking blood glucose is below 100 mg/L, you’re likely in good metabolic health.
Fasting glucose is a powerful indicator of your metabolic health. As the chart below from Jee-Jeon et al., 2017 shows, a fasting glucose level between 80 and 100 mg/dL tends to align with the lowest hazard ratio or the lowest risk of dying from any cause (all-cause mortality).
Although people tend to experience worsening metabolic health and increased glucose levels as they age, the relationship between optimal fasting glucose and hazard ratio remains the same, regardless of age or gender.
Why Is My Waking Glucose Higher on a Low-Carb Diet?
We typically see people on a lower-carb diet have higher waking glucose. This is because your body releases stored glucose into the bloodstream overnight to prepare you to wake up and get going in the morning. But, as shown in the hourly chart below from the Data-Driven Fasting app, glucose drifts down during the day.
If you tend to show higher waking glucose values, prioritising more protein and fewer carbs earlier in the day keeps blood glucose lower and improves satiety. When blood sugar is lower later in the day, you can strategically use some carbs when your glucose is significantly below your personalised glucose trigger.
Additionally, boosting blood glucose a little before bed can improve sleep and prevents overnight hypoglycaemia. This is because extra carbohydrate before bed tends to raise insulin overnight, which leads to lower waking glucose. Conversely, more fat in your last meal often leads to higher waking blood glucose levels the next day.
If you see slightly higher waking glucose on a lower-carb diet, you do not need to be too concerned so long as your other markers (e.g., body weight, BMI, post-meal blood glucose, Hb1Ac) are OK.
Low-Fat Diet Glucose Pattern
Conversely, people on a lower-fat diet tend to see lower waking glucose but higher numbers later in the day.
Because carbs are a more volatile fuel source, we cannot store them as easily as we do fat (i.e., we must burn them off). As a result, you tend to burn through them throughout the night, leading to lower waking blood glucose. For more, check out Oxidative Priority: The Key to Unlocking Your Fat Stores.
People on a higher-carb diet also tend to see higher glucose values during the day. While it’s not ideal to have high glucose after you eat, it’s more important to focus on your overall average glucose level. As we will see, the best way to do this is by managing your glucose before you eat.
How Can I Make Better Food Choices Using My Blood Sugars?
The table below shows the guidance our Data-Driven Fasting app gives about what to eat based on your current blood glucose.
|Post-Meal, Above Upper Limit||You overfilled your glucose fuel tank. Next time, try eating less of that food/meal or eliminating it from your repertoire.|
|Significantly Above Trigger||Wait! You don’t need to eat yet! You have plenty of fuel on board.|
|Just Above Trigger||Ideally, wait to eat unless you’re particularly hungry. In this case, prioritise nutrients and protein and consume less energy from carbs and fat.|
|Just Below Trigger||Eat ‘normally’.|
|Significantly Below Trigger||Prioritise enough carbohydrates to quickly alleviate extreme hunger from low glucose and bring glucose back into your normal range.|
Before long, following this simple approach will stabilise your energy levels and increase satiety without having to throw yourself into a dietary extreme like a low-carb or low-fat diet.
How Low Is Too Low When It Comes to Blood Glucose?
When they start testing their blood glucose, many people wonder ‘how low is too low?’
According to the CDC, a blood glucose level below 55 mg/dL (3.0 mmol/L) is severely low and considered hypoglycemia. However, you’ll be unlikely to get to this level without taking excessive amounts of medication like exogenous (injected) insulin or prolonged fasting.
As you can see from the data above, these critically low levels do not occur in our Data-Driven Fasting Challenges because participants use their glucose values to validate their hunger and eat before their blood glucose gets too low.
What Happens When Blood Sugar Is Too Low?
When you don’t have enough glucose in your bloodstream to fuel your brain and muscles, you may feel shaky, tired, dizzy, anxious, moody, and — most likely — starving!
Blood sugar shoots up quickly after a high-carb meal. This causes the body to release insulin to halt the release of stored energy until the excess blood glucose is used up.
But this increase in insulin can lead to a rapid drop in blood glucose two or three hours after your last meal of the day, eventually contributing to feeling poorly and extremely hungry.
Consequently, you will feel drawn to energy-dense foods and lack the discretion to make smarter choices that will give your body the Goldilocks amount of energy (not too much, not too little!) to bring your blood glucose back into the normal range.
This is why we suggest dialling back your intake of processed carbohydrates if your glucose rises by more than 30 mg/dL (1.6 mmol/L) after eating. Once your blood sugars stabilise into the normal healthy range, you will regain healthy appetite signals.
However, it’s important not to swing to the other extreme! Swapping out all carbs and protein for fat to flatline blood sugars can cause you to lose touch with healthy appetite signals and cause you to overconsume calorie-dense fat because of its low satiety value.
How Can I Quickly Raise My Blood Glucose?
People with diabetes often use glucose tablets or dextrose to quickly bring their blood glucose back into range. Sugar, soda, and fruit are not as effective because a considerable percentage of their sugar content is from fructose, which is metabolised differently and requires extra steps before it becomes glucose.
For most people, whole food is better. As the table above shows, the DDF app will suggest you include starchy carbs like rice or potato if your blood sugar is significantly below your normal.
If You Feel OK, You Are OK!
When it comes to low blood sugar and not injecting insulin, you generally are OK if you feel OK. You don’t need to be concerned about lower blood glucose levels, particularly if you’re lowering them gently.
We designed Data-Driven Fasting with this in mind, so people could stop pushing their fasting so hard that they drive their blood sugars to such extreme lows that they end up making poorer food choices.
While we’ve given DDF the name Data-Driven Fasting, it could also be called glucose-guided eating because people are taught to hold off on eating just long enough to tap into their stored glycogen and fat. As they continue to follow this guidance, they develop regular, sustainable eating patterns that allow them to lower their blood sugars, lose body fat and improve their metabolic health.
What Is the Most Important Glucose Number to Manage?
As we’ve mentioned, your waking (or fasting) glucose is one of the most critical metrics for monitoring your overall metabolic health. However, it’s hard to control your waking glucose. While reducing the amount of fat in your last meal or stopping eating earlier tends to lead to lower waking glucose, it doesn’t really address the root cause of elevated waking glucose: energy toxicity.
As shown in the chart below, your BMI and fasting glucose are proportional. Therefore, the more stored energy you have, the more energy tends to be floating around in your bloodstream early in the morning. Hence, finding a way to offload some extra energy you have on board so you can lose body fat tends to lower waking glucose over time.
People with a greater BMI tend to require their pancreas to produce more insulin throughout the day.
For more on the role of insulin, check out:
- What Does Insulin Do In Your Body?
- The Real Reason You’re Insulin Resistant and The Macros to Reverse It, and
- Personal Fat Threshold Model of Insulin Resistance, Diabetes and Obesity vs the Carbohydrate Insulin Model.
Waking Glucose vs Pre-Meal Glucose
As shown in the chart below, our analysis indicates that waking glucose is highly correlated with pre-meal glucose.
Fortunately, you can manage your waking glucose by modifying when and what you eat. As you gradually chase a lower pre-meal glucose number over time, you will begin offloading some of the extra weight you have on board.
Waking Glucose vs Post-Meal Glucose
Compared to pre-meal glucose, the association between waking and post-meal glucose is not as strong. In other words, putting all the focus on manipulating your post-prandial glucose values will likely not help you lower critical metabolic health indicators, like your waking (fasting) glucose or reduced body fat level.
Waking Glucose vs Glucose Rise After Meals
We also see a very weak correlation between waking glucose and the rise in glucose after eating.
Although you can ‘hack’ your glucose and tame your continuous glucose monitor (CGM) by swapping carbs and protein for fat, it won’t help you decrease your weight or improve your metabolic health. Instead, it might make things worse!
When your blood sugar drops between meals, your body dips into stored glycogen and fat. Without this dip, you will essentially continue to stockpile energy.
Some glucose variability is normal and healthy! We just want to avoid the large, erratic swings.
Optimising when and what you eat to manage your pre-meal glucose is a much more effective way to:
- improve your metabolic health,
- lower your waking glucose, and
- lose weight.
How to Optimise Your Blood Glucose
Finally, let’s look at how you can use your pre-meal glucose to reach your goals and achieve your desired results.
After you find your baseline glucose trigger using the DDF app, it guides you through Hunger Training. As the chart below from the DDF app shows, you simply wait until your blood glucose indicates you need to refuel.
If you can successfully wait until you reach your personalised glucose trigger more often than not, you will begin to unload some of the energy you have stored. As a result, your average pre-meal glucose value will start to decrease, and the DDF app will slowly reduce your trigger to ensure you keep progressing.
The real magic of Data-Driven Fasting is that it gets you back in touch with your true hunger signals, which so many people have fallen out of touch with.
Once you relearn what it feels like to truly be hungry without pushing yourself so hard that you end up in a binge, you can get on with your life without having to constantly use your blood glucose as guidance. You have successfully retrained your hunger signals.
When you log your pre-meal trigger in the DDF app, you also get the chance to rate your hunger level. Lower glucose readings tend to align nicely with higher perceived hunger ratings.
As we can see in the chart below from the Data-Driven Fasting data analysis, people who eat when their blood glucose is closer to 90 mg/dL feel hungrier than when their glucose is 100 mg/dL.
But before you try to use the numbers here, remember that your metabolism is unique! To find your personalised pre-meal blood glucose trigger, you can click here for two weeks of free DDF app access.