When your “normal” blood sugar isn’t normal (Part 1)

November 12, 2010 in Diabesity | View Comments

childhoodobesityIn 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.” Diabetes, like all disease, 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.

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.

  • http://evolutionaryhealthsystems.blogspot.com Tyler

    Hi Chris- been reading your blog for a while, I’ve used the information from here to treat clients with really excellent results. Your research quality and the application of it is really top notch.

    Quick question – I’m 180 lbs, intercollegiate sprinter/jumper, following a strict evolutionary diet for ~10 months, diet was very good before that too, about 8-10% body fat, and overall in great health. However in my last blood test, my A1c was 5.7%. I tested BG values for 2 weeks afterwards and it only went over 126 twice, and was usually between 80-90 (while eating my normal lowish carb diet). The doctor was completely stumped as to why my A1c was so high, as am I. My other blood values were normal- TGs: 48, LDL: 91, HDL: 111.

    Any ideas off the top of your head as to why this would happen?

    Thanks a lot for the great info on the site by the way, you are an inspiration.


  • http://evolutionaryhealthsystems.blogspot.com Tyler

    forgot this, but my systemic inflammation is pretty good too, CRP was <0.1.

  • Chris Kresser

    Only thing I can think of that wouldn’t elevate FBG and post-meal BG, but would elevate A1c is dehydration. In this scenario, your hemoglobin would still be in the lab range but outside of what we call the “functional range”, which is the range that reflects optimal health. Polycythemia and erthrocytosis could do the same thing, but in that case your hemoglobin would be outside of the lab range.

    Were you under any additional stress during the previous 3-month period leading up to the A1c test? Cortisol elevations from physical (overtraining) or mental/emotional stress could elevate A1c, but we’d expect to see it in FBG and post-meal sugars as well.

  • http://evolutionaryhealthsystems.blogspot.com Tyler

    I can’t say I remember my hydration status at the time, I’m usually well hydrated but it’s definitely possible that I wasn’t. I’m going in for another one soon and I’ll make sure to hydrate well.

    The previous months were physically stressful as I was doing manual labor all day, training for track, and weight lifting, but not mentally stressful. I was also during intermittent fasting at this time (probably stupid idea considering the workload). Certainly could have elevated cortisol.

    I’ll let you know the results from the next test. I really appreciated the answer, thanks again.


  • http://www.wildeaboutsteroids.co.uk/ Margaret Wilde

    Dear Chris

    I’m not well-informed on this important topic, so please excuse my question. You write that “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.” – Is this absolutely permanent? – Or does the bonded hemoglobin eventually get broken down so that the person ‘gets another chance’ at regaining unglycated hemoglobin?

    Thank you very much for your interesting and informative blog.


  • Chris Kresser

    A normal life cycle for a red blood cell is 120 days. So when I say “permanent”, I’m just referring to that period of time. It’s absolutely possible to change A1c levels with diet.

  • http://www.wildeaboutsteroids.co.uk/ Margaret Wilde

    Thank you so much for that very cheering information. That’s great news.

  • java

    Amazing article..does a state of fasting , as in early morning blood tests alter scores. Should one ideally hydrate before these tests. But then what is ‘normal’ ? Tests done in a state of hydration or tests done without hydration ?

  • Jesse

    Hey Chris, what research are these tests and numbers based on? It’d be interesting to see how they came up with such values. Or were they just made up from nothing?

  • Chris Kresser

    Jesse: lab ranges are mostly determined by taking a bell curve of the results of those who get tested. And that is a huge problem I will be addressing in a future article.

    Java: eating will affect blood sugar, that’s why to obtain a fasted blood sugar reading (to see how the blood sugar behaves in a fasted state) it is necessary to fast for 12 hours. Many other things, such as cortisol levels, will also affect blood sugar in the fasted state. Being adequately hydrated is a normal physiological state, so yes, you should be adequately hydrated to avoid skewing the results.

  • Tim Huntley

    Hi Chris,

    Thanks so much for this article. I am new to reading your blog, but am very interested in learning more about blood glucose testing. I recently had some blood work done and because of a flaky reading on a fasting glucose test, my doctor reordered the test and an HbA1C test. While she was very pleased with the results (fasting of 90 mg/dl and A1C 5.5%), I thought the A1C seemed high. I purchased a blood glucose meter and have been doing some testing over the past week. So far the highest reading I have seen was 2 hours after eating a breakfast of oatmeal with butter, coconut flakes, cashew butter and about 2 Tbsp of honey. It was 141 mg/dl. That seems fairly high to me (for a presumably healthy person). Thoughts? (and FYI, I ate the same breakfast this morning without the honey and only hit 110 mg/dl)

    My plan is to continue testing after meals that are higher in carbs and see what foods tend to cause the highest spikes.


  • Chris Kresser

    This is exactly what I was talking about in the article. I can’t understand why a doctor would be “pleased” by an A1c of 5.5 when 5.6 is often considered to be pre-diabetic. That’s lunacy. Does some magic button get pushed between 5.5 and 5.6 that changes everything? I don’t think so.

    As I’ll explain in the next article, nerve damage, beta-cell destruction and other complications begin to occur as blood sugars rise over 140 mg/dL. Believe it or not, heart attack risk increases in a linear fashion as A1c rises above 4.6%. Granted, the increase in risk from 4.6% – 5.5% is very mild, but from 5.5% – 6.0% it goes up significantly.

    You may need to reduce your carb intake. There are several other potential causes of high blood sugar, such as high cortisol, so that might be worth investigating as well.


    Tyler the sprinter:

    Test your blood sugar immediately after a high stress workout and you might see an unfriendly blood sugar level.

    Just an idea that could explain the high A1c.

  • http://evolutionaryhealthsystems.blogspot.com Tyler

    Hi Perkdoug- I did test it after several exhaustive sprint workouts and I now know that they definitely elevate my BG for a while. I didn’t really ever get super high readings though, usually between 95-115. I really don’t know how this compares to a healthy BG response to exercise but it doesn’t strike me as too excessive.

    Thanks for the tip.

  • Chris Kresser

    That’s not excessive as a response, but do they return to baseline after 2 hours?

  • http://evolutionaryhealthsystems.blogspot.com Tyler

    Yeah, back down to 83-87 within an hour usually.

  • rmarie

    I am definitely pre-diabetic (have been for at least 10 years that I know of) and yes, my doc never said anything because it was usually well below 126. One of the reasons I’ve never taken an OGTT is that I weigh 89 lbs and I think drinking 75 oz glucose for such a small body is irresponsible. And they probably wouldn’t adjust it. I watch my carbs and things have not gotten worse over all that time. I’m in my late 60′s.

  • Chris Kresser

    I’ll explain how to cheaply and easily measure post-meal blood sugars in a future article, which is probably a more accurate indicator of CVD and diabetes risk than OGTT anyways.

  • rmarie

    Chris, I’ve been wondering about something re A1C tests and BG spikes for which you may have the answer:

    How long does the blood glucose have to be in the blood to bond to the hemoglobin. Is it immediate? For instance if a high BG spike of say 180 is brought back down quickly (without medication) does it have enough time to bond? (and influence the A1c test result)?

    I’m asking because I have learned a little trick. For example, if I eat something I suspect may raise my BG I test it after 1/2 hour and if it’s high, doing 60-80 jumping jacks will lower it 30-40 points within 10 minutes. Works every time and I have NEVER experienced hypoglycemia. My base line tends to stay around 115-120.

    It’s very convenient and quick without having to spend an hour running or bike riding.

  • Chris Kresser


    From what I’ve read, even relatively quick spikes can be harmful, but the effect worsens the longer they are elevated.

    A much better strategy, in my opinion, would be to avoid the spikes in the first place by not eating the foods that cause them, and by working to address the underlying mechanisms. Just my 2 cents.

  • Eva

    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.

  • Chris Kresser

    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.

  • Tim Huntley


    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).

  • Chris Kresser

    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.

  • Jim


    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.

  • Chris Kresser

    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.

  • Pål Jåbekk

    Just noticed this related article today: http://www.ncbi.nlm.nih.gov/pubmed/20627649?dopt=Abstract

  • Chris Kresser

    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.

  • Jim

    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.

  • Chris Kresser

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

  • bentzurm

    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.

  • Chris Kresser

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

  • bentzurm

    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.

  • http://none Vera Volk

    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

  • Chris Kresser

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

  • http://profiles.google.com/jackiepatti Jackie Patti

    A1C does not directly correlate to bg.

    For example, fructose can raise A1C, but not bg – I’m guessing that’s the cause as your LDL is a bit on the high side (gorgeous TG and HDL though).

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