High Fasting Blood Sugar on Keto?

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High Fasting Blood Sugar on Keto?

The more I coach people through a ketogenic lifestyle, the more I become familiar with small nuances that can affect different people’s experience. For example, there are a number of people who experience high fasting blood sugar upon waking in the morning. These individuals would express that they were following a ketogenic diet and were in a fasted state so it doesn’t make sense to have elevated blood sugar.

What you are going to find out in this article is that this effect may actually be much more normal than you think. In fact, it may not even be an issue. That being said, for some people it may actually be a sign of something undesirable going on with their metabolism. This article will help you troubleshoot what is likely to be causing your high fasting blood sugar.

Pathologic Insulin Resistance

When someone has elevated fasting blood sugar and is NOT following a ketogenic lifestyle, it is likely that they are suffering from insulin resistance. Insulin resistance is characteristic of pre-diabetes and diabetes, as well as metabolic syndrome. This is when your cells stop listening to insulin’s signals to let glucose into the cell and instead allow glucose to continue circulating in the blood.

This is often due to a high sugar diet that constantly bombards insulin receptors to the point where they become desensitized. Think “Little Boy Who Cried Wolf”, but with your cells. This is called pathologic insulin resistance as it is considered a disorder and increases your risk of many different diseases.

Insulin Resistance fasting blood sugar

Dawn Phenomenon and Somogyi Effect

In diabetics, there are 2 common ways that high fasting morning blood sugar arises.  The first reason is the “Dawn Phenomenon” and this impacts individuals who are following a ketogenic lifestyle as well.  Overnight as we sleep between the hours of 2-8am a slurry of hormones including cortisol, growth hormone, adrenaline and glucagon all begin to rise.

These hormones cause a gluconeogensis effect where the liver and muscles break down their stored sugar (glycogen) to increase circulating blood sugar.  This helps us have energy and mental arousal in the morning.  This is a normal physiological response and it is normal for keto dieters to have slightly higher fasting blood sugar…although it shouldn’t be too high and you can mitigate this with the strategies discussed further on in this article.

Diabetics who are also taking exogenous insulin can also have something called the somogyi effect where they shoot too much insulin before bed and they have a blood sugar crash, followed by a huge increase in stress hormones that dramatically increases blood sugar through gluconeogenesis.  This is obviously not an issue unless you are a type I or type II diabetic taking prescription insulin.

Adaptive Glucose Refusal

When someone is following a ketogenic lifestyle and is in a fasted state, it is typical that blood sugar levels will be relatively low and stable. However, in some individuals it is possible to have temporary elevations in fasting blood sugar. More often than not, this occurs in the morning when the individual is in a fasted state.

When you are sleeping your body is very active cleaning out the brain and rebalancing hormones. Sometime in the morning between 4-8AM, the body releases cortisol, epinephrine, growth hormone, and glucagon. These hormones all have the effect of increasing blood sugar to wake you up. These hormones may also be released in response to a significant drop in blood sugar during sleep (1).

The difference in those who are following a ketogenic lifestyle is that if they are well keto-adapted, then their cells may refuse to burn that sugar for energy. This will naturally make fasting blood sugar levels seem elevated.

Instead of sugar not being able to get into the cells due to insulin resistance, the cells are simply refusing to burn sugar because they would prefer the ketones already being used. In this case, elevated fasting blood sugar is less of a concern.

Where Does This Blood Sugar Come From?

You may be wondering how your fasting blood sugar can become elevated if you have only been consuming high-fat meals and very little carbs. Well, your body has a built-in mechanism to create its own glucose. This is because there is a small proportion of the body that can only burn sugar as an energy source.

While the rest of the body’s cells are burning ketones for energy, your body will actually use amino acids, lactic acid, and glycerol to manufacture the necessary sugar for those cells. This process is called gluconeogenesis. Additionally, the body will store a small supply of glucose in the liver and muscles in the form of glycogen.

This is why some people are able to stay in ketosis for long periods of time with no consequences, they are still getting all the sugar they need! Some people do seem to do better with a cyclical ketogenic diet, however.

Measuring Blood Sugar Balance

So, as you can see, it is not as simple as looking at a single isolated blood sugar value when determining if your elevated fasting blood sugar is a reason for concern. If your blood sugar is concern to you, there are a number of other values that are actually much more helpful. These include:

Fasting Insulin: A high fasting insulin will be a sign of insulin resistance, especially accompanied by an elevated blood sugar

Hemoglobin A1C (Hb A1C): Gives insight into blood sugar balance over the last 3 months, an elevated value would signify poor blood sugar control and potentially diabetic conditions

C-Reactive Protein: An inflammatory marker highly correlated with blood sugar, an elevated value would signify poor blood sugar balance as well as potential increased risk of several chronic diseases (heart disease, arthritis, psychological disorders, IBS, etc.)

HOMA-IR: This is a key measurement for understanding insulin resistance. HOMA-IR is actually a simple equation that multiplies fasting glucose (in mg/dL) by fasting insulin (in μIU/mL). This total is then divided by 405. The following ranges are then compared:

Less than 1 = Optimal Insulin Sensitivity

Above 1.9 = Early stage insulin resistance

Greater than 2.9 = Significant Insulin Resistance

Essentially, HOMA-IR looks at the relationship between insulin and glucose in your body rather than each as a separate value.  I learned about the HOMA-IR and got the ideas for this graphic below from our friends at Heads Up Health.

Other Factors Affecting High Blood Sugar

In addition to the normal cycle that occurs before waking up, there are a number of other factors that may be influencing fasting blood sugar. After considering the tests above, the following factors should be considered and addressed for optimal blood sugar balance.


If you are under a high amount of stress or are having HPA axis dysfunction, then uncontrolled cortisol secretion could be causing high fasting blood sugar levels. This is because cortisol quickly stimulates the release of glycogen stores to prepare the body for an immediate stressor and increased physical demand.

If you are constantly stimulating cortisol throughout the day due to your stressful lifestyle, then this will likely cause a blood sugar rollercoaster and elevated blood sugar at times.

Reducing your stress load and using other strategies to balance your cortisol levels will be an important step in ensuring this is not the cause of elevated blood sugar. For specific strategies on how to balance your cortisol, here is a great article: 7 Ways to Balance Cortisol Levels


Just one night of poor sleep can be cause for elevated fasting blood sugar the next morning. In fact, poor sleep alone may be responsible for blood sugar readings that mimic those of pre-diabetic conditions (2). Not surprisingly, those who consistently get poor sleep seem to also have higher instances of diabetes (3).

I have a great article titled 7 Lifestyle Strategies for Better Sleep that can be helpful for troubleshooting any sleep issues you are having.

Another common sleep issue that I have seen is mouth breathing and sleep apnea. Mouth breathing and sleep apnea are associated with an increased stress response and poor oxygenation of tissues which can create stress responses and throw off blood sugar. Taking steps to ensure you are breathing through your nose and that your airways remain open throughout the night will be incredibly important.

Using a bit of micro pore tape at night to hold the mouth closed can help to facilitate more restorative nostril breathing.  These SomniFix Sleep Strips recently came out and they are excellent.

Food Sensitivities

A food sensitivity is a low-grade immune response to a particular food. These immune responses may be impossible to feel as they are occurring, however over time they can become an internal stressor on the body and stimulate cortisol, leading to elevated blood sugar.

Each individual will tend to have their own unique food sensitivities, however common sensitivities include: grains (including wheat), cow’s milk, eggs, fish, soy, nuts, and seeds.

One way to find your food sensitivities is to have them tested through functional lab work. A simple and inexpensive way to test for your unique food sensitivities is to perform the pulse biofeedback test as outlined in this article

Controlling for Monitor Accuracy

Oftentimes I have seen that certain blood sugar monitors can have off readings every now and then. If you have an elevated reading that seems unexpected, take the same measure 2 more times and average the values, oftentimes an elevated reading can be a monitor malfunction.

Other things to consider are any kind of residues that are present on the surface that you tested. For example, if you recently held a piece of fruit or used a product that contained sugar (soaps, artificially scented products, etc.) then this can also throw off your monitor.

Make sure you wash the testing area thoroughly before testing and take multiple readings to ensure accuracy.

Monitoring both ketones and fasting blood sugar can be extremely helpful as well. This is because if your ketones are elevated at the same time as a slightly elevated blood sugar reading, this is a good gauge that you are still in ketosis. As I describe above, this scenario may be more likely to be adaptive glucose refusal. My favorite 2-in-one monitor is the Keto Mojo.


Your level of hydration is going to have an impact on the concentration of things that are dissolved in your blood, including glucose. This means that a high blood glucose could simply be due to dehydration. To address this matter, simply follow these guidelines for daily water consumption:

At least half of your bodyweight in lbs should be consumed in ounces of water per day. Ideally this would even reach your full bodyweight.

Start your day with what I call super hydration. Before consuming your first bite of food, drink 16-32 oz of water to hydrate your body, flush out your system, and stimulate a bowel movement. If you are someone who does intermittent fasting, feel free to increase this amount.

I often recommend for those who fast until noon or later to consume around a gallon of liquids in the form of water, organic broths, herbal teas, and coffee.

Additional Strategies to Balance Blood Sugar

Blood sugar balance is critical for optimal health. Along with addressing the factors discussed above, the following are additional strategies to ensure you maintain stable blood sugar.

Many of these strategies are simple to incorporate into your daily and weekly schedule.

Apple Cider Vinegar or Lemon

The naturally occurring acids found in apple cider vinegar and citrus fruits, namely acetic and citric acids, are a cheap and powerful way to balance blood sugar (4, 5). One of the most effective ways to use these is to simply add them to your food and water.

Vinegar and lemon juice go great in many different dishes as a marinade, a dressing, or simply drizzled over top. I will often sprinkle these over a good grass-fed steak or salad to help assist in digestion and absorption as well.

Putting lemon juice and a bit of stevia in your water is another great refreshment to have throughout the day to satisfy your sweet tooth and stabilize blood sugar at the same time.

Prolonged Fasting

Fasting is one of the quickest and most effective strategies for restoring blood sugar balance and possibly improving fasting blood sugar. This is because it provides a rest for insulin receptors and allows for a deeper state of ketosis.

While performing an intermittent fast every day can be helpful, I will often recommend performing a 24-48 hour fast once per week to kick the benefits of fasting to the next level.

A common eating schedule I see a lot of success with is where one consumes a ketogenic style meal plan from Monday to Saturday, consumes a higher carb meal on Saturday night, and follow that up with a 24 hour fast from Saturday dinner to Sunday dinner.

High Intensity Exercise

Getting your blood pumping with some high-intensity exercise 2-4 times per week can have a powerful impact on your blood sugar balance. This is because when placed under a high demand, your muscles will rapidly burn up any available sugar available, improving insulin sensitivity in the process (6).

Another helpful strategy if you tend to have elevated blood sugar after meals is to take a light 10-minute walk. The muscle activity may activate a glucose transporter named GLUT 4 which will help ensure excess blood sugar is stored in the muscle tissues (7). Over time, remaining physically active may improve fasting blood sugar levels.

Improve Vitamin D Levels

A commonly overlooked aspect of blood sugar control is Vitamin D levels. Low Vitamin D levels are commonly associated with poor blood sugar control. It appears that supplementation with a high-quality Vitamin D supplement may help with elevated blood sugar in some individuals (8).

Increasing your exposure to the sun is also helpful for improving Vitamin D levels. Ideally, you would want your Vitamin D levels to fall between 60-100 ng/ml. In my experience, most individuals are well below this range unless they have taken active steps to improve their levels.

Assess Thyroid Health

The thyroid is the master controller of the metabolism. The way your brain and thyroid communicate to determine the expression of your thyroid hormones ultimately dictates your ability to burn fat and stabilize blood sugar to a large extent.

There are many different factors that can influence your thyroid hormones including stress levels, liver health, nutrition, and paradoxically, blood sugar.

If you have poor blood sugar control and chronically elevated insulin levels, this will likely place stress on the liver. The liver has the important job of assisting the conversion of the inactive thyroid hormone (T4) into its active form, T3. If this function is inhibited and the metabolism slows, burning and balancing blood sugar becomes more difficult. It then becomes apparent how this can turn into a viscous cycle.

Luckily, your thyroid status can be easily tested along with several other markers mentioned in this article (Vitamin D, fasting blood glucose, fasting insulin, Hb A1C, and CRP). In fact, all of these markers can be found in one lab, our Complete Thyroid Report.


High fasting blood sugar on a ketogenic diet may not be of huge concern. In fact, it may be a sign that your body is adapting well to burning fat for fuel!

To be sure that you are not having other complications, additional measures of blood sugar balance are mentioned in this article including: HOMA-IR, Hb A1C, and CRP.

Finally, using additional strategies to balance blood sugar as mentioned above is a great way to ensure your fat burning engines stay primed.

Sources for this Article Include

1. Rybicka M, Krysiak R, Okopień B. The dawn phenomenon and the Somogyi effect – two phenomena of morning hyperglycaemia. Endokrynol Pol. 2011;62(3):276-84. PMID: 21717414
2. Gan Y, Yang C, Tong X, et al. Shift work and diabetes mellitus: a meta-analysis of observational studies. Occup Environ Med. 2015;72(1):72-8. PMID: 25030030
3. Katsa ME, Ioannidis A, Zyga S, et al. The Effect of Nutrition and Sleep Habits on Predisposition for Metabolic Syndrome in Greek Children. J Pediatr Nurs. 2018. PMID: 29402659 
4. Radulian G, Rusu E, Dragomir A, Posea M. Metabolic effects of low glycaemic index diets. Nutr J. 2009 Jan 29;8:5. PMID: 19178721
5. Brighenti F, Castellani G, Benini L, Casiraghi MC, Leopardi E, Crovetti R, Testolin G. Effect of neutralized and native vinegar on blood glucose and acetate responses to a mixed meal in healthy subjects. Eur J Clin Nutr. 1995 Apr;49(4):242-7. PMID: 7796781
6. Sjöros TJ, Heiskanen MA, Motiani KK, et al. Increased insulin-stimulated glucose uptake in both leg and arm muscles after sprint interval and moderate-intensity training in subjects with type 2 diabetes or prediabetes. Scand J Med Sci Sports. 2018;28(1):77-87. PMID: 28295686
7. Richter EA, Hargreaves M. Exercise, GLUT4, and skeletal muscle glucose uptake. Physiol Rev. 2013;93(3):993-1017. PMID: 23899560
8. Scragg R. Vitamin D and Type 2 Diabetes: Are We Ready for a Prevention Trial? Diabetes. 2008;57(10):2565-2566. doi:10.2337/db08-0879.

Dr. Jockers

Dr. David Jockers is a doctor of natural medicine, functional nutritionist and corrective care chiropractor. He currently owns and operates Exodus Health Center in Kennesaw, Georgia. He has developed 6 revolutionary online programs with thousands of participants.



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  1. How can I safely intermittent fast when having HPA Axis dysfunction and hypothyroidism and seemingly, blood sugar issues though I do not consume any sugar? There seems to be such a fine line with how long I fast and just how bad my body might feel ( ice cold hands, white noise and ringing pressure in my ears and head mostly). If it were not for these symptoms, I would easily do 20/4 or 24hours fasts to ultimately heal my body. My intention is to do just that and I would love any suggestions on how to titrate up in my fasting windows without stressing my body. Thanks for much, for your site, your videos and for listening right now!


      1. Thank you ! Though I’ve read and reread that great article, I always skipped the simple and cycle fast options. I dove right in at 16/8. And to think I considered myself a patient person! Thank you for slowing me down to be more safe and realistic!

  2. Very informative article. Thank you. I have been doing fairly strict keto with a 16 hour fast every day for 3 months. I have lost 25 pounds but my fasting morning glucose has been high. I have been prediabetic in the past but sugars never higher than 100. Now they are 130-140! I haven’t checked glucose later in the day, just want to know how concerned to be. I will definitely have my doctor order those tests to mentioned. Will also try the lemon water at night.

  3. Is it possible that apple cider vingegar could actually cause too low blood sugar and possibly stimulate a “rebound” gluconeogenesis/higher blood sugar after the initial drop?

  4. Thank you for the post. Are there any long term studies or data on the high and increasing FPG in people on keto diet? That’s, will FPG continue to rise with time and convert to frank DM in few years?

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