Can Ketogenic Diet Raise Blood Sugar?

Most of the people diagnosed with T2DM consuming low carb or keto diet (low carb and high-fat diet) will show improvement in their blood glucose level.

Personally, there was a drastic decrease in my blood glucose level after starting the keto diet. In fact, I reversed my T2DM following keto diet.

But some people with T2DM despite having a low carb or keto diet are unable to reduce their blood glucose level. So, what are the reasons despite having a low carb or keto diet they are unable to reduce their blood glucose level? Is it something to worry? Let’s find out in this article.

One of my clients was on a low carb diet but her blood glucose level was high despite controlling her diet. She is 62 years old lady diagnosed with T2DM. She was also on anti-diabetic medication. Initially, she showed some improvement following a low carb diet, but after a few months, her blood sugar level was again raised.

She called me one fine day and asked “Doctor, I am following a strict low carb diet as suggested by you. I don’t think I am having any junk food or processed food, nor I eat much. Still, my fasting blood sugar level is a bit high. Do I need to increase the dose of my drugs?”

Let’s understand what could be the possible reasons.

There could be various reasons for raised blood sugar even on a low carb diet.

Adaptive Glucose Sparing

One of the commonest reasons for the increase in the blood sugar level in the morning is adaptive glucose sparing. This is also known as physiological insulin resistance and it is different from pathological insulin resistance.

I will discuss physiological insulin resistance in details in another blog. For the time being, let’s understand in brief what is physiological insulin resistance also known as adaptive glucose sparing.

When you are following a low carb or keto diet for a long duration, your body starts using a different source of energy called ketone bodies. In a normal individual who is not on a low carb diet, the preferred source of energy is glucose.

Since you are on low carb diet for a long time, the preferred source of energy is ketone bodies. Now, even when you consume very less carb your body still produces glucose through a process called gluconeogenesis. Your liver usually does this by converting protein or other non-carb sources. However, your muscles are not accepting this glucose for two reasons. One is it is now fat adaptive and uses fat as a source of energy. The other is since it thinks that there is not much of glucose in the body, so it keeps it reserved for the brain.

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Thus, when you test your fasting blood sugar level, you find it to be raised.

My client called me and “Doctor, my fasting blood sugar level is very high 136 mg/ld. and my post prandial blood sugar level is 148 mg/ld. I am a bit concerned why by fasting sugar is high”.

My reply to her was “Relax, it’s perfectly fine. Nothing to worry! Please don’t take any stress. It is a normal phenomenon. Then I explained the above process”.

Dawn Phenomenon

Another possible reason for raised blood sugar level in the morning could be ‘Dawn Phenomenon’.

Now you might ask me “What is Dawn Phenomenon”.

I would say that this is a valid question. This is a medical term and most of the doctors would know this. However, for a lay person, it might be a new term. Let me try to explain you in a very simple way.

This is a very natural process that occurs in your body first thing in the morning. This usually happens in response to several hormones like cortisol, growth hormones, adrenaline, and glucagon in the morning.

Now, this is not something which happens only to people with T2DM. This also occurs in individuals who are not resistant to insulin. However, in normal individuals, it drops very fast while in subjects with T2DM it drops gradually.

So, if you are T2DM you must have observed that your fasting blood sugar is high but your post prandial blood sugar level is within normal limits.

I am sure your doctor must have asked you to do a HbA1c test. So, what is the HbA1c test or why is it done or advised by your doctor?

HbA1c test actually measures the average glucose level in your blood over the previous three months by counting the number of glucose molecules attached to your red blood cells. If you are on a low carb diet for a long time, your HbA1c will be much lower than your fasting blood sugar level.

This means that your blood sugar is absolutely under control and there is nothing to worry about.

Glucometer might be faulty

This is also a very common reason for raised blood sugar level.

You should consider a variation of 15% in your results. For example, if your blood sugar level is 120 mg/dL, then it could be as low as 102 mg/dL or as high as 138 mg/dl.

A similar experience was shared with me by another client of mine. He told me “Doctor, I tested my fasting blood sugar level today with two different glucometers”.  He mentioned the names too, but I am not able to recall now. “One glucometer showed 132 mg/dL and the other showed 154 mg/dL. I have measured at the same time”.

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So, you can see that one individual measuring blood sugar level at the same time by two different glucometers showing different results.

So, if sometimes your blood sugar level is low or high you need not panic. There could be many other reasons why your glucometer is not giving the actual reading. 


Just today someone in a diabetes group one lady asked “Anyone on an antipsychotic and have elevated levels? No matter what I do, my levels stay elevated!

To her query, I replied “Can you please tell which antipsychotic drug you are taking. Can you please share your eating habits?” She replied, “Latuda. I do low carb under 24 grams a day on average but most days under 20. Eat my meal at night cuz that’s when I’m hungriest. Protein fat and sometimes a few veggies. Been doing low carb since March so I don’t understand. My average blood glucose according to the meter is 98 but I’m still convinced that is high for a normal person”

I replied, “I think it is very normal. Please don’t take any stress. 98 is a good number. In fact, I consider fasting BS level less than 110 mg/dL and PP BS under 150 mg/dL perfectly fine. We should not overcorrect BS as there could be a high chance of hypoglycemia. So please relax. You are doing fine. Keep following low carb diet. Have you checked your blood insulin level? If not, I would suggest getting your blood insulin level checked. that will give a clear picture.”

HOMA-IR stands for homeostatic model assessment of insulin resistance. The HOMA-IR gives us a clear picture of how hard your body needs to work in order to maintain homeostasis which means how much insulin is required to keep your blood sugar level in the normal range?

How is HOMA-IR is calculated? There is a formula to calculate HOMA-IR.

Glucose in mass units (mg/dL)

HOMA – IR = (Glucose x Insulin) / 405

Glucose in molar units (mmol/L)

HOMA – IR  = (Glucose x Insulin) / 22.5

Insulin produced in your body is constantly working against glucose in an attempt to keep your blood sugar levels stable.

The above formula will give you the reading for HOMA-IR. So, what does the reading say?

If HOMA-IR is ≤ 1 it means you have excellent insulin sensitivity and if the reading is ≥ 2.75 it means your insulin resistant. If it is between 1 and 2.75 it means you have an average insulin sensitivity.

Let’s understand this further with an example.

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Mrs. X ’s fasting glucose level is 98 mg/dL and fasting insulin level is  7 μIU/mL while Mrs. Y’s fasting glucose level is 86 mg/dL and fasting insulin level is 18 μIU/mL.

So from the reading, we can see that Mrs. Y’s fasting glucose level is much lower than Mrs. X’s and it is vice versa for fasting insulin level.

Now we apply the above formula and interpret the result.

Mrs X’s HOMA-IR = 98 x 7 / 405 = 1.69

Mrs Y’s HOMA-IR = 86 x 18 / 405 = 3.82

The results clearly show that although Mrs. X’s blood glucose level is much higher than Mrs. Y’s, she has an average sensitivity to insulin while Mrs. Y is resistant to insulin despite much lower fasting glucose level.

From this calculation, we understand that fasting blood glucose or HbA1c might be misleading and HOMA-IR gives us a better picture of whether you are at higher risk of developing metabolic complications in the future.

Latent Autoimmune Diabetes in Adults (LADA)

Finally, if none of the above reasons are raising your fasting blood sugar, then you may be suspected to have LADA.

I am not going to talk about LADA in this article. I will soon write an article on LADA in details.

Take away message
  1. If your fasting blood glucose level is raised after following a low carb or keto diet for quite some time, then there is no need to worry.
  2. Rather you should not take any stress because of your raised blood sugar level, you should have good sleep and do some exercise to stay healthy.
  3. Maybe you increase your carb intake for some time and as you become more sensitive to insulin, your blood sugar level will be within normal limits.

If you have enjoyed reading this article, please like and share with your friends and family. If you have any comments please type in the ‘Leave a Reply’ box and I will surely respond to your query.

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