High Fasting Blood Sugar On Low Carb

HRBS-glucometersI have been on a Low Carb High Fat (LCHF) diet for over 3 years. Lost 35 pounds and have kept it off during this time frame.
I use a 16/8 fasting regimen and eat 2 meals a day. The amount of carbs I consume on a daily basis is so low it borders on ketogenic. 20 to 30 grams a day, I am almost in ketosis.

I went into the lab on Friday to get my bi-annual blood panel. A couple of hours later, I tested at home on my glucometers, 6.7 mmol/L – 120 mg/dl. WTF. I could not believe it. Have my trusty glucometers let me down?  Is there glucose on my fingers?  Try it again and get the same reading. I have a Contour Next EZ and an ACCU-CHEK Aviva that I mainly use because they are accurate.

Monday, I checked my lab results and was absolutely shocked. My Fasting Blood Sugar (FBS) was 7.0 mmol/L – 126 mg/dl on the Richter scale. Then another shock, my doctor called me to discuss the blood work up. So I made an appointment to see him a few days later.

Why So High?

Why do I have a high fasting blood sugar on a low carb diet? Should I be worried or is there an explanation? Even though, I’m following a low carb diet and starting to understand the irregularities of high blood sugar in a fasted state. For someone that sticks to a low carb diet and has such a high fasting blood sugar, doesn’t mean cheating. There are many reasons for this and other ways to determine metabolic health.

Going back to Sunday, 5 days before the test, my FBS was 5.1 mmol/L – 92 mg/dl. Wednesday 2 days before 5.5 mmol/L – 100 mg/dl and then on Friday, test day 7.0 mmol/L – 126 mg/dl.  So as not to confuse you, blood sugar is the same as blood glucose and glucose.

Dawn Phenomenon and Somogyi Effect

There are  2 common explanations in diabetics for high fasting blood sugar (hyperglycemia) in the morning. The first reason is the Dawn Phenomenon and affects people on a low carb/keto diet. As we sleep hormones become active between 1 and 8 am. Through the process of gluconeogensis the liver breaks down glycogen, (stored glucose) and puts back into the blood system. This is a normal response causing the blood sugar to rise.

The second reason is the Somogyi effect, exogenous diabetic insulin users inject too much insulin before bed. The result is hypoglycemia (blood sugar drops too low) followed by stress and then a blood sugar spike[1].  Diabetic insulin users must be aware of this issue.

Adaptive Glucose Sparing

Physiological insulin resistance otherwise known as adaptive glucose sparing, is not the same as pathologic insulin resistance. Pathologic insulin resistance is higher levels of insulin, also known as hyperinsulinemia. Hyperinsulinemia is associated with obesity, hypertension, metabolic syndrome, type 2, diabetes and many chronic conditions.

People that follow a low carb/keto lifestyle and fasting will have low stable blood sugar. In the morning blood sugar will usually be higher, as the day goes on it will eventually come down. When glucose was available from the abundance of carbohydrates the cells would burn glucose. However on a low carb/keto diet the cells will burn fat for energy instead.

Thus, cells will not need insulin to burn glucose for energy. Excess glucose will be circulating in the blood for organs that need glucose. For example the brain is one of the biggest users of glucose.

Other Blood Measurements

Insulin levels, if your insulin sensitivity is normal and you have a higher fasting blood sugar, means you are good. One measurement is not the deciding factor. Now if your insulin is high and fasting blood sugar is high that is a whole different story. There are of course other measurements that we should consider like HgA1c, triglycerides, hypertension, and HDL. These numbers should all be considered and if they are all low, then something else is going on.

The test we need to investigate is the HOMA-IR.

HOMA-IR stands for Homeostatic Model Assessment of Insulin Resistance. Use the calculator from Dr. Richard Maurer’s site The Blood Code.(2)

On this page there are 2 calculators the first is the HOMA-IR the second is the Heart Disease calculator


On your next blood panel workup have the above tests performed including fasting insulin and fasting blood sugar.  All of the tests are important so get them done. Once you have your fasting insulin and fasting blood sugar plug them into Richard’s formula. Now figure out your insulin resistance, and heart disease risk.


What is cortisol?  Cortisol is a stress hormone secreted from the adrenal glands called glucocorticoids. the adrenal glands sit above the kidneys, and have two areas. The adrenal cortex is one and has several zones that produce cortisol.

Cortisol will be generated from stress and will stimulate insulin and will ultimately affect blood sugar.(3)


Researchers from the Harvard Business school published a report that found workplace stress causes 120,000 deaths in the US. The costs associated are close to $200 billion in health care expenses.

Stress comes in many forms from physical, (fasting); psychological, (worrying); or environmental (air pollution); and will increase cortisol levels.

Metabolic Effects of Elevated Cortisol and blood sugar
– Reduced transport of glucose into cells
– Decreased insulin sensitivity (increased pathological insulin resistance)
– Increase in appetite and carbohydrate cravings

There is no need to worry about any of the above if you are on a low carb /keto diet.


The CDC reports that up to 70 million Americans suffer from lack of sleep. Worldwide 25 % have this same issue. Lack of sleep will lead to health problems. Most people, about 90 % need between 7 to 9 hours of sleep per day. Surprisingly the other 10 % can do with less.(4)

Problems with our daily lives could be affecting the way we sleep, which leads to stress. You need to get enough sleep. Additionally, one hour of lost sleep can increase cortisol levels by 50 percent and will play havoc with insulin.

Glucometer Accuracy

There are many factors that can affect the reading on your glucometer. If you are not sure take another reading. I use 2 of the most accurate glucometers on the market and as you can see the readings are identical. The Contour Next EZ; and the ACCU-Chek Aviva are highly recommended and simple to use. Furthermore, other factors that can alter reading on your glucometer are soaps or fruits with high amounts of sugar.

You must wash your hands thoroughly with soap and rinse clean with water before you do a blood test.

In Summary

I started doing my taxes Wednesday night and worked on it until Saturday, which accounted for the high stress levels. I though I was going to owe a lot of money so in the end brought it to my accountant. She worked on it for about an hour and I ended up paying a lot less. Next time I will bring it to her with all the paperwork in a shoebox and let her take care of it.

Should I be worried about my high fasting sugar on low carb? Of course not, because my A1c was 5.4 and my fasting insulin was 43 pmol/L or 6.2 mU/L.  My insulin sensitivity is a little over 1 but I am working on lowering it.  My stress level is back to normal until next year at tax time. So let me ask you a question.  Do you understand the difference between physiological insulin resistance and pathological insulin resistance?  Should you be concerned? Let me know in the comments.

Finally, moral of the story, let your accountant do your taxes and you will not have any stress.

I appreciate question, comments and concerns.

Thanks for dropping by and viewing.


  1. The dawn phenomenon and the Somogyi effect – two phenomena of morning hyperglycaemia. Rybicka M1Krysiak ROkopień Bhttps://www.ncbi.nlm.nih.gov/pubmed/21717414
  2.  https://www.thebloodcode.com/calculators/
  3. The Cortisol Connection Diet: The Breakthrough Program to Control Stress and Lose Weight, Shawn Talbott, Hunter House; 1 edition, September. 20 2004.
  4.  Sleep: EXACT BLUEPRINT on How to Sleep Better and Feel Amazing Brain Health, Memory Improvement & Increase Energy,


Recommended Reading (See Recommended Books To Read)

Harper’s Illustrated Biochemistry Thirty First Edition McGraw-Hill Education, Victor W. Rodwell, David Bender,  Kathleen M. Botham,  Peter J Kennelly,  P Anthony Weil, May 18, 2018.

The Blood Code: Unlock the Secrets of Your Metabolism, Dr. Richard Maurer, The Blood Code, March 12, 2014.

The Cortisol Connection Diet: The Breakthrough Program to Control Stress and Lose Weight, Shawn Talbott,  Hunter House; 1 edition, September. 20 2004.

Sleep: EXACT BLUEPRINT on How to Sleep Better and Feel Amazing Brain Health, Memory Improvement & Increase Energy, Brian Adams, CreateSpace Independent Publishing Platform, November 16 2015.

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6 thoughts on “High Fasting Blood Sugar On Low Carb”

  1. Thanks for the good information. 

    My father has been suffering from diabetes since 2017. I didn’t know how to care for him at first but now I’m getting used to it. When he gets stressed, cortisol is released and insulin is secreted.

    It could be dangerous because low blood sugar leads to hypoglycemia and could be fatal. So it’s very important for a diabetes patient to control stress. This article explains this important fact very well.

    Thanks for your effort.

    1. Hello Grey,

      Stress reduction is a very important factor for diabetics. People that lead high stressful lives will find it very hard to lower insulin and may remain insulin resistant and diabetic.

      The other important factors are eating a low carb high fat diet, exercising, sleep and lifestyle. The goal is to get off of medication and to lead a drug free lifestyle. 

      Please check out my Low Carb High Fat Diet page for further information and also check out my Recommended Books To Read.

      Thanks for viewing and your comment.



  2. I enjoyed reading through this article. I am Diabetes 2, 60 years young and my levels are way too high.

    I have bookmarked this post and will come back and spend more time on this site as I know you are offering some really great info here and I need to get my levels down as my organs are paying the price.

    Thank you so much for this post and for what your site is all about 🙂

    1. Hello Vicki,

      I appreciate your kind words, not sure if you understand the post. The issue that caused my high fasting blood sugar was the stress of my tax return. Stress caused insulin and insulin kept my blood sugar high. My fasting blood sugar on a daily basis is around 5.0 t0 5.5 mmol/L or 90 to 100 mg/dl.

      I am curious, what kind of blood panel numbers do you have?   A1c, triglycerides, fasting insulin, HDL, ALT, and fasting glucose. 

      What are you doing to take care of your type 2 diabetes? Taking medication? Dieting? Exercising? 

      Thanks for dropping by and reading.


  3. I saw a youtube video the other day on Tom Bilyeu channel. His guest speaker was a doctor (do not remember his name) but he was talking about high blood pressure and high blood sugar, when you do Keto and IF. He mentioned that the numbers are only high right after you eat because of the food you have ingested. It should go down right after you eat. It doesn’t matter if you eat high protein or carbs the body still produces insulin and that is why your blood pressure or sugar are high. Basically he said the same thing that you say.

    I think we should just not to worry too much about the numbers. We should go with how we feel, are we out of breath? Do we have energy? We know our body best and I think we should go from there. I am also following the IF but I do not follow Keto but I do eat very low carbs. I feel good about myself and I have lots of energy. I think everyone should practice fasting.

    1. Hello Nuttanee,

      We are going in different directions here. I totally agree that carbs and protein stimulate insulin. Carbs more than protein as protein is converted to glucose through the liver. Carbs are of course sugar.

      For people that follow a Low carb/Keto diet and intermittent fasting, numbers do matter, but when the fasting blood sugar is out of whack due to stress, cortisol is the problem. The solution is to remove the stress so that your fasting blood sugar will come down.

      Leading a high stressful life will keep your cortisol high and therefore insulin will be high. This will definitely affect insulin resistance and other metabolic issues, for example type 2 diabetes as in my case.

      My fasting blood sugar on Monday was normal and my blood workup fasting insulin was low. Also my A1c was 5.4. Normalized numbers.  

      If I may ask, curious to know, what are your numbers?

      Thanks and appreciate your comments.


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