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.
 

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34 comments

  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.

    Replies: #18, #31
  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.
    Ronit
    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.
    Kathleen
  17. Troy
    Cindy Long - when the pancreas is insulin resistant it produces glucagon even in presence of food and during fasting. Liposomal GABA can be used to help improve sensitivity of pancreas. Take it when fasting - may require high doses so start small and titrate up accordingly!
  18. Amy
    Hi Peter, do you have a source on the liver information presented here? Many Thanks

    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.

  19. Amie
    Hi just wanted to tell anyone who is reading to not give up and I pray you all get better! God bless you all!
  20. Barbara
    Thank all of you for this great info. It really helps to know I am not alone. Strict keto 8 weeks and fasting sugars are over 200. Much worse than with normal healthy foods and meds.
    I know it will get better, but none of the medical professionals or health coaches have offered any explanation.
    God bless all of you!
    Reply: #33
  21. Andre
    I’ve been keto for almost 4 months and my fasting blood sugars range from 105-125 and my blood sugar throughout the day is 105-135. My A1C was 6.1 at the 3 month mark. I don’t know why my blood sugars can’t get below 100.
    Reply: #22
  22. Kristin Parker Team Diet Doctor

    I’ve been keto for almost 4 months and my fasting blood sugars range from 105-125 and my blood sugar throughout the day is 105-135. My A1C was 6.1 at the 3 month mark. I don’t know why my blood sugars can’t get below 100.

    You may want to monitor your blood sugar before and after meals to see if what you're eating is inadvertently keeping your numbers higher than you would like. You may also find this helpful.
    https://www.dietdoctor.com/blood-sugar

  23. Peggy
    I've been LCHF for 7 years (dx with prediabetes at that time) and monitoring ketones for last 1 1/2 years. In the past week my fasting blood sugar, normally in the low 100's suddenly jumped to 140's even as ketone levels hold between 0.5 and 1.5. I eat around noon and early evening, usually protein and a vegetable or Greek yogurt with few berries. This week blood glucose tends to start dropping early afternoon to around 115 but then creeps back up through the evening. My last A1c was 5.1, from two months ago. I feel well otherwise and no other health issues but I am baffled by this new development. I have a very low tolerance for abnormal glucose levels! Part of me says cool it and just watch for now. The other part wants to fix it NOW. Any ideas as to what might be going on?
    Reply: #24
  24. Kristin Parker Team Diet Doctor

    I've been LCHF for 7 years (dx with prediabetes at that time) and monitoring ketones for last 1 1/2 years. In the past week my fasting blood sugar, normally in the low 100's suddenly jumped to 140's even as ketone levels hold between 0.5 and 1.5. I eat around noon and early evening, usually protein and a vegetable or Greek yogurt with few berries. This week blood glucose tends to start dropping early afternoon to around 115 but then creeps back up through the evening. My last A1c was 5.1, from two months ago. I feel well otherwise and no other health issues but I am baffled by this new development. I have a very low tolerance for abnormal glucose levels! Part of me says cool it and just watch for now. The other part wants to fix it NOW. Any ideas as to what might be going on?

    As this is a new development, it may be worth checking in with your physician.

  25. Peggy
    Thank you for your response. I think I've resolved it! It appears to be a bad lot of strips. I had already replaced my monitor thinking that was the problem. My husband suggested switching to a different lot of strips and voila! Numbers returned to expected levels and finger sticks taken at the same time with the "bad" strips are consistently 20 - 40 points higher. I'll continue to monitor but I feel pretty confident that is the issue. Note to self: look for simple solutions first!
  26. Peggy Nestor
    My conversation with the strip manufacturer was quite enlightening so I wanted to share. I had purchased my meter and strips from Amazon. The customer rep says they have been having issues with strips purchased from Amazon giving faulty readings. Even the "new" meter I purchased a few days ago is actually an expired product that was manufactured in 2011! The company is making it right and sending me a replacement meter, strips, and control solution. She is also sending me a list of reliable distributors. I have to admit I have skipped the control solution for the last few years and presumably that would have picked up my problem strips right away. So lesson learned!
  27. Kenn frye
    Hi, I am 54 type 2 have had two strokes in 2018, I have been one meal a day for three weeks, when I do eat my meal is 6 oz sirloin steak, and only water and black coffee to drink, my blood glucose level is around 174 after fasting in the morning, and ranges for 125 - 220 throughout the day, what am I doing wrong? I walk in the a.m 2.5 miles and again 1.5 at night, my doctor is no help!!!
    Reply: #28
  28. Crystal Pullen Team Diet Doctor

    Hi, I am 54 type 2 have had two strokes in 2018, I have been one meal a day for three weeks, when I do eat my meal is 6 oz sirloin steak, and only water and black coffee to drink, my blood glucose level is around 174 after fasting in the morning, and ranges for 125 - 220 throughout the day, what am I doing wrong? I walk in the a.m 2.5 miles and again 1.5 at night, my doctor is no help!!!

    I have two articles to share with you that may help shed some light. First is our guide to protein, please review it to see where your protein needs are https://www.dietdoctor.com/food-policy/protein The impact protein has on an individual will vary greatly. It may be that you need to consume other foods along with the protein depending on how lean the steak is.

    Here is our link to our one meal a day guide. https://www.dietdoctor.com/intermittent-fasting/omad It does not sound like you're eating very much food. You may be stressing your body.

  29. Shari
    My mom started keto diet. Her sugars were in the 119-145. Dr.suggested her to try it due to get AC1 being a 7.1. Now her sugars are only 59. She has no energy clammy and sleepy but can't sleep at night.
    She has lost 5 pds in 3 days. I'm sure it's water. But I'm concerned on sugar level of 59. After eating lunch they went to 49. I made her drink a bit of orange juice. What is happening?
    Doctors staff said no appt for a week😢
    Reply: #30
  30. Crystal Pullen Team Diet Doctor

    My mom started keto diet. Her sugars were in the 119-145. Dr.suggested her to try it due to get AC1 being a 7.1. Now her sugars are only 59. She has no energy clammy and sleepy but can't sleep at night.
    She has lost 5 pds in 3 days. I'm sure it's water. But I'm concerned on sugar level of 59. After eating lunch they went to 49. I made her drink a bit of orange juice. What is happening?
    Doctors staff said no appt for a week😢

    If your mother is on any medication for her diabetes, she will need to work with her medical professional as keto can work quickly to reduce blood sugar. https://www.dietdoctor.com/low-carb/with-diabetes-medications

  31. Pablo Cohen
    After days of searching your symptoms are exactly like mine. Any chance you could give me the reference of where you read about the liver been insulin resistant? I have been running for 6 months 7-14 miles per day and Went from 175 to 152 lb. but my A1C was 7 months ago 6.4 and now it’s barely 6. And my glucose average daily is about a 116-20 at fasting and after half marathons. Sometimes it will hit 90. I just can’t make sense of this contradiction.
    Reply: #32
  32. Crystal Pullen Team Diet Doctor

    After days of searching your symptoms are exactly like mine. Any chance you could give me the reference of where you read about the liver been insulin resistant? I have been running for 6 months 7-14 miles per day and Went from 175 to 152 lb. but my A1C was 7 months ago 6.4 and now it’s barely 6. And my glucose average daily is about a 116-20 at fasting and after half marathons. Sometimes it will hit 90. I just can’t make sense of this contradiction.

    Please see Dr. Fung's response to the first question in this Q & A. https://www.dietdoctor.com/why-is-blood-glucose-elevated-when-fasting

  33. LaWanda
    I am T2 and have been doing keto for about 6 weeks with little or no carbs and IF and my blood sugar is 200 every morning. But later, it goes down to about 160. It's scary and I know my doctor will try to add another pill. What can I do?
    Reply: #34
  34. Kristin Parker Team Diet Doctor

    I am T2 and have been doing keto for about 6 weeks with little or no carbs and IF and my blood sugar is 200 every morning. But later, it goes down to about 160. It's scary and I know my doctor will try to add another pill. What can I do?

    Please make sure to work with your doctor regarding your medicine dosage.

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