A streamlined stack of supplements designed to meet your most critical needs - Adapt Naturals is now live. Learn more

When Your “Normal” Blood Sugar Isn’t Normal (Part 1)


In the next two articles we’re going to discuss the concept of “normal” blood sugar. I say concept and put normal in quotation marks because what passes for normal in mainstream medicine turns out to be anything but normal if optimal health and function are what you’re interested in.

Here’s the thing. We’ve confused normal with common. Just because something is common, doesn’t mean it’s normal. It’s now becoming common for kids to be overweight and diabetic because they eat nothing but refined flour, high-fructose corn syrup and industrial seed oils. Yet I don’t think anyone (even the ADA) would argue that being fat and metabolically deranged is even remotely close to normal for kids. Or adults, for that matter.

In the same way, the guidelines the so-called authorities like the ADA have set for normal blood sugar may be common, but they’re certainly not normal. Unless you think it’s normal for people to develop diabetic complications like neuropathy, retinopathy and cardiovascular disease as they age, and spend the last several years of their lives in hospitals or assisted living facilities. Common, but not normal.

In this article I’m going to introduce the three markers we use to measure blood sugar, and tell you what the conventional model thinks is normal for those markers. In the next article, I’m going to show you what the research says is normal for healthy people. And I’m also going to show you that so-called normal blood sugar, as dictated by the ADA, can double your risk of heart disease and lead to all kinds of complications down the road.

The 3 Ways Blood Sugar Is Measured

Fasting blood glucose

This is still the most common marker used in clinical settings, and is often the only one that gets tested. The fasting blood glucose (FBG) test measures the concentration of glucose in the blood after an 8-12 hour fast.

It only tells us how blood sugar behaves in a fasting state. It tells us very little about how your blood sugar responds to the food you eat.

Up until 1998, the ADA defined FBG levels above 140 mg/dL as diabetic. In 1998, in a temporary moment of near-sanity, they lowered it to 126 mg/dL. (Forgive me for being skeptical about their motivations; normally when these targets are lowered, it’s to sell more drugs – not make people healthier.) They also set the upward limit of normal blood sugar at 99 mg/dL. Anything above that – but below 126 mg/dL – is considered “pre-diabetic”, or “impaired glucose tolerance” (IGT).

Oral glucose tolerance test (OGTT)

The OGTT measures first and second stage insulin response to glucose. Here’s how it works. You fast and then you’re given 75 grams of glucose dissolved in water. Then they test your blood sugar one and two hours after. If your blood sugar is >140 mg/dL two hours later, you have pre-diabetes. If it’s >199 mg/dL two hours later, you’ve got full-blown diabetes.

Keep in mind these are completely arbitrary numbers. If your result is 139 mg/dL – just one point below the pre-diabetic cut-off – you’ll be considered “normal”. Of course this is perfectly absurd. Diabetes isn’t like catching a cold. You don’t just wake up one day and say, “I’m not feeling so well. I think I got a bad case of diabetes yesterday.” Like all disease, diabetes—and diabesity—is a process. It goes something like this:

malfunction > disease process > symptoms

Before your blood sugar was 139, it was 135. Before it was 135, it was 130. Etcetera. Would you agree that it’s wise to intervene as early as possible in that progression toward diabetic blood sugar levels, in order to prevent it from happening in the first place? Well, the ADA does not agree. They prefer to wait until you’re almost beyond the point of no return to suggest there’s any problem whatsoever.

[End rant]

The other problem with the OGTT is that it’s completely artificial. I don’t know anyone who drinks a pure solution of 75 grams of glucose. A 32-oz Big Gulp from 7-11 has 96 grams of sugar, but 55% of that is fructose, which produces a different effect on blood sugar. The OGTT can be a brutal test for someone with impaired glucose tolerance, producing intense blood sugar swings far greater than what one would experience from eating carbohydrates.

Like what you’re reading? Get my free newsletter, recipes, eBooks, product recommendations, and more!

Hemoglobin A1c

Hemoglobin A1c, or A1c for short, has become more popular amongst practitioners in the past decade. It’s used to measure blood glucose in large population-based studies because it’s significantly cheaper than the OGTT test.

A1c measures how much glucose becomes permanently bonded (glycated) to hemoglobin in red blood cells. In layperson’s terms, this test is a rough measure of average blood sugar over the previous three months.

The higher your blood sugar has been over the past three months, the more likely it is that glucose (sugar) is permanently bonded to hemoglobin.

The problem with the A1c test is that any condition that changes hemoglobin levels will skew the results. Anemia is one such condition, and sub-clinical anemia is incredibly common. I’d say 30-40% of my patients have borderline low hemoglobin levels. If hemoglobin is low, then there’s less of it around to become bonded to glucose. This will cause an artificially low A1c level and won’t be an accurate representation of your average blood sugar over the past three months.

Likewise, dehydration can increase hemoglobin levels and create falsely high A1c results.

The “normal” range for A1c for most labs is between 4% and 6%. (A1c is expressed in percentage terms because it’s measuring the percentage of hemoglobin that is bonded to sugar.) Most often I see 5.7% as the cutoff used.

In the next article we’ll put these “normal” levels under the microscope and see how they hold up.

ADAPT Naturals logo

Better supplementation. Fewer supplements.

Close the nutrient gap to feel and perform your best. 

A daily stack of supplements designed to meet your most critical needs.

Chris Kresser in kitchen
Affiliate Disclosure
This website contains affiliate links, which means Chris may receive a percentage of any product or service you purchase using the links in the articles or advertisements. You will pay the same price for all products and services, and your purchase helps support Chris‘s ongoing research and work. Thanks for your support!


Join the conversation

    • Absolutely blood sugar levels can and DO increase when you are sick. Any stress, including illness, can trigger hormonal changes that elevate our blood glucose. Mine typically rises 10-15% during times of illness.

  1. i monitor my bg daily when my diabetic husband does his. my bg always is between 60 – and no higher than 111. i had lab work done and my bg was 104. my a1c was 10.0. the dr. said i am diabetic! how is this possible? i am in good health, lift iron, rollerskate, dance, bike and trikke. will be adding swimming this winter too. i am 68 and feel fit and healthy. i eat low carb, lean meats and lots of veggies. no grains or milk. but allow yogurt. my husband had the blood work done at same time. his glucose is always over 300. it has been as high as 600. his a1c was 6.5. do you think they could have had a mix up? i am very confused. can you help?

    • Something is certainly confused there. When I was diagnosed as a Type II diabetic my fasting BG was 267 (much higher post-prandials) and my HbA1c was 12.1%.

      The 10.0% HbA1c converts to a 24hr average blood glucose level of 240 mg/dl. The 6.5 converts to 140 mg/dl.

      The 10.0 is most-certainly a diabetic number. Depending on who you talk to the 6.5 is considered diabetic or pre-diabetic. In my opinion, it’s most certainly a diabetic number.

      Both the IDF (International Diabetes Federation) and the AACE (American Association of Clinical Endocrinologists) state that 140mg/dl is where damage starts to occur, and both recommend that even post-prandial (after-meal) numbers stay NO HIGHER than the 140mg/dl level. Myself, I like to see my post-prandials no higher than 120mg/dl.

      • Hi Glen,
        I just found out that my fasting blood sugar is 267. I typed it into google and was brought here to this discussion board. Can you offer some encouragement by telling me what you have done to improve your health (diet/meds) and what your numbers are now? I feel overwhelmed. Thanks.

    • Boy, I’d have loved to hear the rest of that story! If the “BG is always”‘s were correct, does sound like maybe some blood samples were mislabled.

  2. I have Sjogren’s Syndrome and am afraid that I may be coming up with Type I diabetes.
    My fasting blood sugar as measured by glucometer is in the high 90s (95-99).
    My HbA1c was 5.4%.
    While those numbers alone wouldn’t get me clinically diagnosed, my fasting BG levels have been rising, I have urinary urgency, +ANA (1:160), weight loss, dry mouth, dry eyes (that may be due to SjS).

    I understand that Type I diabetes may have a rapid onset of months to even weeks.
    What would be the best set of tests to determine whether my immune system is attacking my islet cells and I am losing the ability to produce insulin. Would I have to just wait for the effects to show up or are there tests that show specifically if this process is taking place.

    • Hi John,
      I have Sjorens Disease, too. The dry mouth and eyes is part and parcel to the illness.

      As for your numbers, you need to see an Endocrinologist ASAP to discuss those concerns. My numbers are similar to yours.

      Type 1 is an auto-immune issue where the body attacked the cells of the pancreas responsible for producing insulin.

      Because you already have inflammatory auto-immune illness, you do have a greater than average risk of developing other auto immune issues. I’m in the pre-Type 2 diabetic stage. I was diagnosed with Sjogrens, Lupus, Hashimotos and Scleroderma, and Fibroymyalgia all in January, 2009. Once the body begins down that path, you have to pull yourself up by your bootstraps and make many lifestyle changes. It’s just the hand we’ve been dealt in this life, sorry to say.

  3. Hi Chris, in recent months I seem to have succeeded (or so I thought) in lowering my BG levels with dietary changes. I test every morning on waking and at varied times through out the day (before/after meals etc) and have a 90 day average reading of 6.3 which according to the Diabetes uk calculator should give me a HbA1c of about 6. Calculating it with the formula: 90 day av + 2.52 / 1.583 gives a HbA1c of 5.6 yet my results have come back with an HbA1c of 6.9 which would mean my average BG would have to be about 8 – 8.5 and it is never that high. In the last 6 months I’ve quit smoking, lost 22lbs and thought I’d considerably lowered my bg. I feel I could cry, all the effort and then getting that result back.Could the test be wrong?

  4. Vera: stay tuned. Part 2 to follow tomorrow, and another article on the subject next week.

  5. Chris, I read this article on testing blood sugar levels. I am confused about which tests are meaningful for a monitoring, maintenance? My Mom is Type 2 and one nephew is Type 1. I am attempting to understand and monitor Mom’s condition long distance, third person. Thank you, VeraMae

  6. I’m assuming you will delve into how you use post-meal blood sugar in the following posts, so I’ll be patient and save all my questions about that for that post. thanks.

  7. I don’t recommend the OGTT, as I mentioned. I prefer post-meal blood sugar testing using a glucometer.

  8. chris, when talking about OGTT how do you take into consideration the physiological insulin resistance one acquires from being fat adapted via a sane paleo nutrition plan? Both Peter from Hyperlipid and Robb Wolf have written about this. Do you consider it still useful? apart from that I just don’t feel comfortable with giving anyone such a bolus of pure liquified glucose, even for testing sake.

  9. Jim: I don’t see why they wouldn’t be. Alcohol also causes fatty liver, which could explain your lipid profile.

  10. Chris, thank you for the reply. You’re very kind to take the time, not just for me but all the other questions you’ve addressed in the past. And, you also have one of the very best health and nutrition blogs I’ve seen.

    My brother had an interesting observation about the beer consumption: he stated that it seemed to increase when I gave up wheat a few years ago, and we wondered if the exorphin polypeptides present in wheat and barley might be present in beer, as they were in the pasta and bread that I used to “love” to eat.

  11. Great find, Pål. Yes, there are quite a few studies in the literature proving the inferiority of FBG and A1c to OGTT for predicting future diabetes.

  12. Yep, the beer could definitely do it, via impaired liver function. Would also be worth exploring cortisol and other mechanisms, because your diet (aside from the beer) sounds good. A few potatoes a week wouldn’t explain those numbers, which as you know are well into the pre-diabetic range. Testing your post-meal blood sugars on a day when you drink beer, and a day when you don’t, would be a good next step. Also after you eat potatoes.

    • Chris, I was diagnosed with prediabetes over a year ago. This was determined by an A1C test of 5.9.
      My fasting blood sugar was 78 at the time..Ironic, huh?
      After avoiding fruit (only eat berries now and then) and being very low carb, I brought it down to 5.7 by last February. Again, the fasting BS is always good..low to mid 80s. I’ve been now testing at home and most post prandials are in the high 80s or high 90s. I ate one sweet potato with a meal a few weeks ago and my post prandial tested a whopping 143!
      I am giving up all starches because I think they are a problem for me.
      I practice intermittent fasting (16 hours fasting) I follow some of the principles of the Warrior Diet. I would love your opinion on that. Does intermittent fasting do harm or will it help. I lost 8 lbs participating in it. I weight about 110 now. My waist went down to 27 from about 30 or 31.
      I’m 56 and I’ve been working out for 27 yrs. so you can imagine how shocked I was to be slapped with the pre diabetic label. Ok, ok…I was a chronic sugarholic and cut way back on it but obviously not soon enough.
      I do HIIT or Peak8 Cardio and I pump iron. I take after dinner walks almost every night.

      Any other suggestions to come up with a better A1C. My other sugar levels always look great. My last Triglyceride measure was 75.

  13. Chris,

    I had a VAP panel done a couple of weeks ago and was disappointed to find that in the 3 years since the last VAP, I have changed from pattern A/B to pattern B. Subclasses are: LDL4=25.2, LDL3=56.9, LDL1=5.7. My fasting glucose was 117, CRP=2.3, Cystatin C=1.17, A1c=5.6, Insulin=6.9.

    I avoid wheat and other grains, vegetable oils, and do eat meats, coconut oil, pastured butter. In congruence with the Perfect Health Diet, I have begun to eat a bit more starchy carbs like potatoes a couple of times a week and sweet potatoes about once a week. I do drink too many (5 or 6 per day) light beers with about 5 grams carb each. Is that the ‘problem’? Also, I just turned 70YO, don’t take any meds. Any thoughts would be much appreciated.

  14. Tim: your lipid profile looks great to me. I wouldn’t be worried about high LDL if your TG/HDL ratio is good, which yours is. But sure, improving insulin sensitivity is always a worthy goal.

  15. Chris,

    Thanks for the advice re: reducing carbs and investigating cortisol. I thought I was doing pretty good on the carbs (eating a WAP diet), but as I have begun to pay strict attention to everything I eat, it seems I have been eating a lot more than I realized.

    I have also been reading about the enzyme HMG-CoA reductase and how insulin stimulates it which in turn causes the liver to make more cholesterol. Would you expect that lowering average blood glucose levels, which should lead to lower average insulin levels would then lead to lower cholesterol carried by LDL? My current lipids are TC 241, LDL 161, HDL 64, and Triglycerides 64 (and while the LDL is “high”, it is almost all pattern A – big and puffy).

  16. Yes, it’s an exciting time in the field of autoimmune research and treatment. I did see the vaccine study, but because of the danger vaccines can present I’m far more inclined towards using nutritional compounds to regulate the immune system. Huge strides have been made in this regard over the past several years, and especially over the last two to three years. I’m wary of Big Pharma’s role and don’t trust them to prioritize safety and effectiveness over profit – in autoimmune disease or treatment of any other condition.

    • I’m just learning more about pre-diabetes as I’ve had some high numbers in the last while–and have experienced off the charts stress in the last couple of years. You mentioned investigating cortisol levels (which I understand are affected by stress). How is cortisol tested for? Thanks.

  17. Chris, you are so cool for answering everyone’s questions! I learn a lot of additional useful info from the Q and A. Speaking of diabetes, I thought you might find this interesting if you haven’t already heard, but looks like they are working hard and doing very well on an apparent vaccine of sorts for type I diabetes and this approach, if successful could well be also useful for all kinds of other autoimmune diseases. As usual, it focuses on containment instead of prevention or cure, but I would not be very surprised if it became the next big pharm cash cow:
    We can only hope that at least its benefits will outweight damages (fingers crossed). One thing is for sure, there is a very big and growing market for effective autoimmune disease treatment.