Why your fasting blood sugar might still be high on low carb

It’s not too uncommon to have slightly high fasting blood sugar on low carb and keto diets. Is this a problem?

It depends on your insulin levels, as outlined by Dr. Ted Naiman below. If you’re insulin sensitive, and have slightly higher fasting blood glucose, it’s likely just fine.



The dawn phenomenon – why are blood sugars high in the morning?

Low carb for beginners

How to reverse type 2 diabetes


Advanced low-carb topics


Dr. Naiman

Earlier with Dr. Naiman

All earlier posts about Dr. Naiman


  1. rpf
    Interesting but hard to know for oneself since there's no easy way to get your daily fasting insulin that I know of, is there?
  2. Tanya
    I just got a glucose monitor and was a bit worried when I saw my fasting blood sugar-6.9 mmol, almost diabetic. So no need for concern? Will it normalise?
  3. Cathis
    How can i messure the insulinlevel my self?
    Reply: #5
  4. Eddie
    Who created this infograph?

    Are the conclusions (high FBG "not a problem" if insulin profile appropriate) supported by studies?

    What is best course of action for a LCing (keto at time), exercising, daily IFing, man who is concerned about "pre-diabetic" FBG and A1c?

  5. Peter Biörck Team Diet Doctor
    Hi Cathis!

    There are no easy way (like for sugar and ketones) yet to do home testing for insulin levels.

    How can i messure the insulinlevel my self?

  6. Jennifer bowerman
    Am I wrong here? Most doctors don't measure insulin levels. They determine diabetes status based on blood glucose levels and then prescribe insulin or its equivalent to balance off and bring the glucose down. So high insulin is treated with high insulin. Isn't this a message Dr. Fung makes many times in his lectures?
  7. It
    Low carb is why i became hpothyroid. Good luck.
  8. Peter
    I've been reading a lot about this. It could just be an insulin resistant liver that takes time to get rid of it's insulin resistance.

    Insulin resistance can exist at different levels in different organs.

    When the liver is insulin resistant, it thinks insulin levels are lower than they actually are. This can increase glucose production in the liver. Over time because of the insulin resistance, the glucose production set point changes, going higher.

    You won't notice this unless you're fasting.

    Then you go on the keto diet, causing your insulin levels to be lower than what it used to be and adding intermittent fasting causing longer periods of low insulin. Now your liver thinks it has to produce more glucose. It's glucose production set point is too high.

    I think the only way to change insulin resistance in the liver is through eating a lot of vegetables and exercize.

    It takes 3 to 6 or more months to rid your liver from insulin resistance, depending on how bad it is. The rest of your body can have mild insulin resistance while your liver has high resistance. And without lots of vegetables it may not go away at all. (I know that a lot of people on keto don't do the healthy amounts of vegetables required, and just stuff them selves with meat, fat, eggs and dairy products.)

    Just my take on it. I had glucose levels of over 105 every day after 15 hours of fasting. They would be around 85, 4 hours after eating. Now, after 9 months on keto, and below 20% protein, my fasting glucose is below 95.

    High protein intake can accelerate gluconeogenesis I think. Keeping protein below 20% will also help reduce high fasting glucose levels.

  9. Cindi Long
    I'm badly type 2 diabetic, have been on an insulin pump needing 500 units per day when eating SAD, more like 200 units per day when eating better. I've done IF and LCHF a couple times when I was younger and I reversed it. I'm older now, and I tried plant based no oil last year in which I ate ONLY plants, and now trying to IF and eat LCHF is taking forever to work. My concern is that I've had only 20 g carbs daily for the last week and a half, eating only within 6 hours each day, and my blood sugar is still 250 to 300. I feel like that's too high and that I need to cautiously use insulin. Does anybody know of anybody else whose sugar stayed that high for this long? In the past I only needed 3 days to get normal blood sugar with no meds at all.
    Reply: #10
  10. Michelle
    Cindi I’m experiencing this as well. I am eating 20g of carbs per day, taking metformin, basaglar, and Saxenda (for almost 2 weeks now) and my sugar was still 391 this morning and I hadn’t eaten for 8 hours.
  11. Barbara
    I’m experiencing the same issue. I’ve been intaking >35 grams of carbs for the last 5 days and my fasting blood sugar is 168. I’ve been feeling to get out and walk or some type of exercise to burn off the excess sugars.
  12. Barbara
    Oops. I used the wrong sign. I meant (less than) <35 gram of carbs per day.
  13. Ronit
    U need to tighten your diet. I started with 43 units of insulin and 3 oral medications, diabetic for 25 years. I first went to LCHF, and slowly added IF, now I am LCHF and OMAD. It's been 6 months, and I watched my fasting sugars go from 350 to 119. I am now off the insulin, but still on the oral meds. It is taking a long time, but it's working. I also lost 25 pounds in the process. I expect to get off ALL my meds be next year
    I also walk for one hour most days. Be patient, this is a Metabolic Syndrome we are repairing, this WORKS. Be patient dear, and keep at it.
    Reply: #16
  14. Donna
    Hi I am Type 2 diabetic and am experiencing really high fasting blood sugars in the A.M. today it was high at 176.40 . I fast 23/1 and very little to no carbs. My sugars do go down and by 3pm can go as low as 88.20 . 2Hr PP after dinner - my bloods are 91.80 but just feel dismayed with the early morning high fasting levels.
    Reply: #15
  15. Kristin Parker Team Diet Doctor

    Hi I am Type 2 diabetic and am experiencing really high fasting blood sugars in the A.M. today it was high at 176.40 . I fast 23/1 and very little to no carbs. My sugars do go down and by 3pm can go as low as 88.20 . 2Hr PP after dinner - my bloods are 91.80 but just feel dismayed with the early morning high fasting levels.

    You can read more about the Dawn Phenomenon here - https://www.dietdoctor.com/the-dawn-phenomenon

    Some people find that a small amount of protein like cheese or nuts before bed will help bring that number down. If you are on diabetes medication, make sure and work with your doctor on dosage adjustments as needed.

  16. Kathleen
    We sure would like your type of results! We just had pulled pork that I made myself with no sugar or glucose and avocado with lettuce. My husband was 200 glucose afterwards. He’s trying to not use insulin. It’s maddening.

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