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Why Your “Normal” Blood Sugar Isn’t Normal (Part 2)


In the last article I explained the three primary markers we use to track blood sugar: fasting blood glucose (FBG), oral glucose tolerance test (OGTT) and hemoglobin A1c (A1c). We also looked at what the medical establishment considers as “normal” for these markers. The table below summarizes those values.

Fasting blood glucose (mg/dL)<99100-125>126
OGGT / post-meal (mg/dL after 2 hours)<140140-199>200
Hemoglobin A1c (%)<66-6.4>6.4

In this article, we’re going to look at just how “normal” those normal levels are – according to the scientific literature. We’ll also consider which of these three markers is most important in preventing diabesity, diabetes, and cardiovascular disease. But before we do that, I’d like to make an important point: context is everything.

As I mentioned in Part 1 of this article series, there are potential problems with how well these tests are utilized to diagnose diabetes. This is an area that needs further study, but continuous glucose monitoring for the general population may be a better marker.

In my work with patients, I never use any single marker alone to determine whether someone has a blood sugar issue. I run a full blood panel that includes fasting glucose, fasting insulin, A1c, fructosamine, uric acid and triglycerides (along with other lipids), and I also have them do post-meal testing at home over a period of 3 days with a range of foods.

If they have a few post-meal spikes and all other markers or normal, I’m not concerned. If their fasting BG, A1c and fructosamine are all elevated, and they’re having spikes, then I’m concerned and I will investigate further.

On a similar note, I’ve written that A1c is not a reliable marker for individuals because of context: there are many non-blood sugar-related conditions that can make A1c appear high or low. So if someone is normal on all of the other blood sugar markers, but has high A1c, I’m usually not concerned.

With all of that said, let’s take a look at some of the research.

Fasting Blood Sugar

According to continuous glucose monitoring studies of healthy people, a normal fasting blood sugar is 89 mg/dL or less. Many normal people have fasting blood sugar in the mid-to-high 70s.

While most doctors will tell you that anything under 100 mg/dL is normal, it may not be. In this study, people with FBG levels above 95 had more than 3x the risk of developing future diabetes than people with FBG levels below 90. This study showed progressively increasing risk of heart disease in men with FBG levels above 85 mg/dL, as compared to those with FBG levels of 81 mg/dL or lower.

What’s even more important to understand about FBG is that it’s the least sensitive marker for predicting future diabetes and heart disease. Several studies show that a “normal” FBG level in the mid-90s predicts diabetes diagnosed a decade later.

Far more important than a single fasting blood glucose reading is the number of hours a day our blood sugar spends elevated over the level known to cause complications, which is roughly 140 mg/dl (7.7 mmol/L). I’ll discuss this in more detail in the OGGT section.

One caveat here is that very low-carb diets will produce elevated fasting blood glucose levels. Why? Because low-carb diets induce insulin resistance. Restricting carbohydrates produces a natural drop in insulin levels, which in turn activates hormone sensitive lipase. Fat tissue is then broken down, and non-esterified fatty acids (a.k.a. “free fatty acids” or NEFA) are released into the bloodstream. These NEFA are taken up by the muscles, which use them as fuel. And since the muscle’s needs for fuel has been met, it decreases sensitivity to insulin. You can read more about this at Hyperlipid.

So, if you eat a low-carb diet and have borderline high FBG (i.e. 90-105), it may not be cause for concern. Your post-meal blood sugars and A1c levels are more important.

Hemoglobin A1c

In spite of what the American Diabetes Association (ADA) tells us, a truly normal A1c is between 4.6% and 5.3%.

But while A1c is a good way to measure blood sugar in large population studies, it’s not as accurate for individuals. An A1c of 5.1% maps to an average blood sugar of about 100 mg/dL. But some people’s A1c results are always a little higher than their FBG and OGTT numbers would predict, and other people’s are always a little lower.

This is probably due to the fact that several factors can influence red blood cells.

Remember, A1c is a measure of how much hemoglobin in red blood cells is bonded (glycated) to glucose. Anything that affects red blood cells and hemoglobin – such as anemia, dehydration and genetic disorders – will skew A1c results.

A number of studies show that A1c levels below the diabetic range are associated with cardiovascular disease. This study showed that A1c levels lower than 5% had the lowest rates of cardiovascular disease (CVD) and that a 1% increase (to 6%) significantly increased CVD risk. Another study showed an even tighter correlation between A1c and CVD, indicating a linear increase in CVD as A1c rose above 4.6% – a level that corresponds to a fasting blood glucose of just 86 mg/dL. Finally, this study showed that the risk of heart disease in people without diabetes doubles for every percentage point increase above 4.6%.

Studies also consistently show that A1c levels considered “normal” by the ADA fail to predict future diabetes. This study found that using the ADA criteria of an A1c of 6% as normal missed 70% of individuals with diabetes, 71-84% with dysglycemia, and 82-94% with pre-diabetes. How’s that for accuracy?

What we’ve learned so far, then, is that the fasting blood glucose and A1c levels recommended by the ADA are not reliable cut-offs for predicting or preventing future diabetes and heart disease. This is problematic, to say the least, because the A1c and FBG are the only glucose tests the vast majority of people get from their doctors.

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OGTT / Post-Meal Blood Sugars

If you recall, the oral glucose tolerance test (OGTT) measures how our blood sugar responds to drinking a challenge solution of 75 grams of glucose. I don’t recommend this test, because A) it’s not realistic (no one ever drinks 75 grams of pure glucose), and B) it can produce horrible side effects for people with poor glucose control.

However, there’s another more realistic and convenient way to achieve a similar measurement, and that is simply using a glucometer to test your blood sugar one and two hours after you eat a meal. This is called post-prandial (post-meal) blood sugar testing. As we go through this section, the numbers I use apply to both OGTT and post-meal testing.

As the table at the beginning of this article indicates, the ADA considers OGTT of between 140 – 199 two hours after the challenge to be pre-diabetic, and levels above 200 to be diabetic.

But once again, continuous glucose monitoring studies suggest that the ADA levels are far too high. Most people’s blood sugar drops below 120 mg/dL two hours after a meal, and many healthy people drop below 100 mg/dL or return to baseline.

A continuous glucose monitoring study showed that sensor glucose concentrations were between 71 – 120 mg/dL for 91% of the day. Sensor values were less than or equal to 60 or 140 mg/dL for only 0.2% and 0.4% of the day, respectively.

On the other hand, some studies suggest that even healthy people with no known blood sugar problems can experience post-meal spikes above 140 mg/dL at one hour. As I said in the beginning of the article, context is everything and all of the markers for blood sugar must be interpreted together.

If post-meal blood sugars do rise above 140 mg/dL and stay there for a significant period of time, the consequences are severe. Prolonged exposure to blood sugars above 140 mg/dL causes irreversible beta cell loss (the beta cells produce insulin) and nerve damage. Diabetic retinopathy is an extremely common (and serious) diabetic complication. Cancer rates increase as post-meal blood sugars rise above 160 mg/dL. This study showed stroke risk increased by 25% for every 18 mg/dL rise in post-meal blood sugars. Finally, 1-hour OGTT readings above 155 mg/dL correlate strongly with increased CVD risk.

What does it all mean?

Let’s take a look again at what the ADA thinks is “normal” blood sugar:

Fasting blood glucose (mg/dL)<99100-125>126
OGGT / post-meal (mg/dL after 2 hours)<140140-199>200
Hemoglobin A1c (%)<66-6.4>6.4

But as we’ve seen in this article, these levels depend highly on context and whether all markers are elevated, or just a few of them.

If you’re interested in health and longevity – instead of just slowing the onset of serious disease by a few years – you might consider shooting for these targets. But remember to interpret the numbers together, and also remember that blood sugar is highly variable. If you wake up one morning and have a fasting blood sugar of 95, but your A1c and post-meal numbers are still normal, that’s usually no cause for concern. Likewise, if you see a one-hour post-meal spike of 145 mg/dL, but all of your other numbers are normal, that is also usually no cause for concern.

Fasting blood glucose (mg/dL)<86*
OGGT / post-meal (mg/dL after 2 hours)<120
Hemoglobin A1c (%)<5.3

*If you’re following a low-carb diet, fasting blood sugars in the 90s and even low 100s may not be a problem, provided your A1c and post-meal blood sugars are within the normal range.

Another key takeaway from this article is that fasting blood glucose and A1 are not often reliable for predicting diabetes or CVD risk. Post-meal blood sugars are a more accurate marker for this purpose.

And the good news is that this can be done cheaply, safely and conveniently at home, without a doctor’s order and without subjecting yourself to the brutality of an OGTT.

I’ll describe exactly how to do this in the next article.

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Join the conversation

  1. Hey Everyone! So I just got back my A1C level and it came out to very, very high (7.9). This was extremely shocking to me since I have no family history of diabetes, am 26, not overweight (125 pounds – 5’5), and eat very healthy, organic foods (generally a low-carb diet).

    I’ve been testing myself everyday prior to seeing my PCP and my fasting blood glucose was at 88, and all post meals have been in the 80s. Have you guys seen this before? Just want to have some sort of idea prior to walking into that doctor’s office next week. Please let me know!

    • I read your story and it was exactly what happened to me. I did everything “right” by medical standards, and yet was pre-diabetic. The way I reversed it is realizing that fats are not bad. Carbs are. I have now been on a keto diet (80% fat) for 1 month and my FBG this morning tested at 85mg/dL. You can do this too. Just remember this simple fact. Fats are critical for life and will do you no harm unless you combine them with lots of carbs, Protein is also critical for life. Carbs are completely optional

      • Ahhh the enthusiasm of the newly converted Keto absolutists! Presh.

        You realize your meter could be off by 20%, right?

        You realize now you have your lipid panel to deal with on Keto, right?

        I’m sure you’re praying your lipids don’t matter and that it’s only “your fluffy large particles that matter” or you’re up the creek.

        LOL vegetable and fruit carbs are not “completely optional” in a person claiming they’re interested in health.

        My complete diet is vegetable/fruit carbs with low healthy fats and low-ish protein and my numbers are GOOD.

    • This was already covered in the article. Did you READ IT?

      How low carb is “low carb” by your standards. How many carbs?

    • Also how long have you been getting these number? If you didn’t have a HIGH glucose, before…a doctor will NOT usually order an A1C.

      So why did you have one?

  2. Hi Chris, I greatly enjoyed your article on blood glucose variations. I’m a scientist, degree in Astrophysics and work in
    laser fusion. I’m diabetic. Found out about 8 years ago. My weight is 150 and height 9ft1/2in. I control my glucose through diet and can vary it pretty much anyway I want. I do not take medication. I have done many glucose tests on myself. The one that puzzles me is described here. Morning before breakfast 119, an hour later 90, 2and 1/2 hours later 97. This is not uncommon. I feel fine during this time. My diet is pretty consistent and is based roughly off Barry Sears Enter the Zone book. Is this behavior common? What causes it? Thanks

    • Reseach “dawn phenomenon” Its actually very common for diabetics to have their highest blood sugars first thing in the morning

    • Your weight is too low for a 9 ft 1/2 person. You could try reducing your height.
      Laser fusion, great, Where are the fusion power plants? perhaps the calculations are off a decimal?

  3. Puzzled.

    I posted previously about my elevated a1c which showed up last year (6.1). Since then, I dropped weight and started an aggressive strength training program. I saw an endocrinologist who ran my fasting insulin and looked for signs of LADA. My fasting insulin was normal (3) and my a1c dropped to 5.2%. The doctor didn’t see any antibodies for adult type 1 diabetes and when I asked the doctor to explain the results; the doctor said my body is processing sugar just fine.

    Did strength training revenue insulin resistance? That was the original diagnosis.

    Are there any other tests that I should inquire about? Have I lost any beta cells?

    I used to spike above 160 (1 hr) and 140 (2 hour) after a decently loaded carb meal (and before weight training). Now I don’t. I’ll hit 130 after 1 hour and 110 at 2 hours when I have a similarly carb loaded meal.

    Aside from my food tests. I’m on a very low carb diet.

    I posted to this forum so that those on track for type 2 can read this. For many, cutting body fat and building muscle may be the solution.

    I appreciate your comments/advice.


    • Hi Austin – Did you ever get any answers? I think I am a lot like you, though I haven’t had an endo check me for antibodies in 4 years. (Going soon.) I eat very low carb but my fasting blood sugar and A1C are still elevated. (100-120 fasting and recent 5.8 A1C.) So frustrating. Looking for ideas and more resources.

    • You wrote, “Since then, I dropped weight and started an aggressive strength training program.” Then you asked if strength training reversed your insulin resistance. Don’t you think that losing weight has much to do with with your much improved BG numbers?

  4. Hi There – I eat a low carb higher fat diet. After 10 hrs of fasting I woke up and took my measurements. It was 2.9mmol when I woke up. I have issues sleeping and waking up a lot and I’m trying to determine if my blood sugar is to slow.

    I tested after a basic meal of fish and veggies (1hr after) and I was 5.6mmol

    It’s great it’s not high but how do you know if it’s too low?

  5. So I got my A1c test results today,and it came back as 5.6. However,I keep a journal of the results of my blood glucose tests that i take on my monitor,and my fasting ranges are between 140-300..once it got as high as 596. Then 2 hours later,it was 375,so still a bad number to be at. My blood sugar never goes below 140,which is confusing because my A1c test came back at 5.6..And my blood glucose tests after I eat meals,always spike up at least 30-40 points. I’ve had 5 readings that came back with numbers higher than 200,and that was with no food in my system. I still have to take the glucose tolerance test..and trust me,i know my body well enough to know how bad my blood sugar spikes after I eat a meal..So my question is,if my A1c test came back normal,though I’m still getting high blood sugar readings with no food in my system,does this mean I could have an undiagnosed case of Diabetes? I also have high triglyceride levels as well. Any advice would be greatly appriciated..

    • A1C results are not accurate is you are even slightly anemic. There are a few other conditions that cause this also. A glucose tolerance test is far more accurate.

    • While A1c of 5.6 usually maps to Blood Glucose between 110 and 120, in some individuals it will correspond to average levels above 150 mg/L. You may be one of them. I think the larger question is whether high BG or high A1c is thought to be associated with long term risks associated with diabetes. I speak as a novice, but from what I’ve read I think the A1c is the more important measure. If your blood generally doesn’t become gluconated over time (what A1c measures) then what does it mater that BG (measured at any given instant with a glucose meter) is consistantly high?

    • Debra is right and depending on the cause of the anemia A1c could be either higher or lower. A1c can also be effected by other factors, such as drug interactions, even hyperglycemia. Why your A1c appears to be, and/or what is causing it to be low is something you probably will want to discuss with your doctor, and he/she can order tests to confirm whether it is reliable, such as fructosamine, A1a, A1b, and etc., as well as tests for anemia if suspected.
      Another possibility is that the meter is off or the test strips are bad (not to mention that technique may cause erroneous highs). Home meters can differ from Lab results by 15% even when functioning properly, but even then 15% off of 300 is still high. The first step here is to test with someone else’s supplies (or use a lab) to verify the readings you are getting are correct.
      The point I made earlier is that not being typical is not always a bad thing, that is assuming both A1c and BG results are correct, and it is a possibility that they both are. Which better reflects a state of health? A1c is the “gold standard” primarily because it is the most studied and is inexpensive. As a time averaged indicator of BG it may better predict complications resulting from consistently high BG. Meters, on the other hand, or instantaneous readings of BG are very useful for identifying what effects BG, like foods, timing, stress or behaviors. Modifying or eliminating such factors feed back into lowering the long-term average BG thereby reducing risk of complications. Meter readings are like daily quizzes; A1c is like a semester grade. The one results in the other, the object being to improve both.
      Most instructive at this point would be using the meter to try and identify what lowers BG readings and identify patterns rather than worry about the specific numbers. Once results are achieved which are consistently lower it will be interesting to see how that impacts upon a future A1c test. Eventually, an accurate A1c cannot be further reduced in spite of ever lower and lower BG meter readings.

    • Those blood sugar levels are much too high. Go to a doctor as soon as possible.

  6. The veterans administration has labeled me diabetic. They took my blood after I slept for 2 1/2 hours up late the night before slamming Pepsi playing video games and rolled in there eating a bag of honey BBQ potato chips. I had no clue they were going to test my A1c and glucose. I told them I just ate they said it won’t matter. My test was through the roof 297 glucose 8.8 A1c. Now here’s the question I’ve got, I’ve never experienced any symptoms of being a diabetic like ever, I can eat like absolute crap and nothing happens. So long story short the VA scares the ever loving shit out of me. I keep saying hey I’m pretty sure you guys botched my test, they don’t listen try to put me on medication I say nope to that, I buy a tester and start sticking the hell out of my finger daily. And after every meal and randomly throughout the day I get the following values 100, 104, 110, 107. Now bear in mind I ditched the soda and have only eaten food I make now for the last 4 weeks. I go back to them in May so they can monitor my diabetic condition…. the 30th I see a civilian doctor for a second opinion. I just have major doubts that I have an issue. I’d say the issue I had was I can’t eat like a 20 year old anymore. Any way wouldn’t mind some input and thoughts on this. I intend to follow up here with the results from the civilian doc.

    • So you’ve made some positive changes. Good for you! Be sure they check your A1c again in May and you should be able to see it has improved because of those changes. However, with your 8.8% last time there’s little doubt about your diabetes. While the 297 reading means nothing because you just ate, the A1c is an average created over the previous 3 months and is unaffected by what you just ate. When you test at home the reading you get before you eat should be near the reading 2 to 3 hours after you eat. Because we don’t know the circumstances of your 100plus Glucose readings its impossible to comment on them, but if you were fasting they’re not in the “normal” (i.e. non-diabetic) range. It’s not bad to try diet and exercise in lieu of medication when you’re first diagnosed but even with those changes most people eventually need to add medication as they age and their diabetes progresses. When, what and how much is what makes us all different. Good luck!

      • After eating and taking my blood glucose test 1-2 hours after eating for the last 4-5 weeks it has returned a value daily between 90-113. So far the highest readings I’ve gotten correlate to when I’ve had bouts of PTSD and stress 182 and 184 I’ve only seen those numbers once on the same day, I took a random sample and pretty much dug myself into a deeper state of depression that day.

        My earlier post was not very clear those tests were taken after eating an hour ish after.

        Today I believe I am not diabetic how on earth can a diabetic continue to have normal values????

        My fasting levels the last 3 weeks have been between 78-92.

        Something else is going on and the veterans administration tried to put me on metformin from a single a1c test and said Dude your type 2.

        More to come my appointment is fast approaching the 30th

        I’ll be showing my civilian doctor the readings from my one touch meter.

        My life style changes however have helped significantly my blood pressure went from being 120/86 down to 108/68. Those were my readings before hand surgery yesterday.

  7. I just want to share a personal revelation. My fasting glucose levels kept being 110 up to 130. Post prandial was always normal. So I started a examining the different things I did before bed. One thing I did before bed was to take my blood pressure medicine Cozaar. I decided to start taking it in the morning instead. Ever since then my fasting glucose level has been below 89. This morning it tested at 77.
    I hope this helps someone!

  8. I’ve been told I have pre-diabetes and I certainly do not want this to keep going in the wrong direction. Last blood test was A1c 5.8 and 101 glucose. I’ve been testing my glucose levels according to your suggestion on and off for a few months to see if I can track the culprits. My fasting blood sugar is always between 94-111 (mostly 101+). It never rises beyond 120 even 45 minutes after a meal except when I tried eating just brown rice. Then it rose to 140. In the evening after a meal and a glass of wine it’s only 80. I’ve tried no carbs at all, no alcohol, Berberine, etc. and can’t seem to figure out what is causing these erratic numbers. I eat 90% Paleo and have also read about the dawn phenomenon so have tried a snack before bedtime. I’ve also tried intermittent fasting. The lowest AM reading I’ve ever had was 87. But there is no rhyme or reason to the patterns so I can’t figure out what is causing this. I do have low cortisol as well as low steroid pathway hormones and wondering how/if this relates. Any insights/suggestions on how to turn this around so it’s not continually creeping up would be appreciated.

    • Carla, most people have what I call red flag foods. We know that it is the carbohydrates that effect the blood sugar levels. Carbs are found in all our foods except our protein sources like eggs and your meats,some veggies, Is very low in nuts and cheese. The good new is carbs are our bodies main source of energy for our cells. There is very little symptoms to diabetes so most people do not really know. Being tired all the time is one of the few symptoms people experience. The amount of carbs in the rice, because it is a starch can push the b.s. levels higher. If you would balance the carbs with some source of protein and a little fat you might not notice such a high. And it could be that rice is one of your red flag foods. Two hours after you eat anything, if you get a spike like that, then monitor that food closer, how much did you have and what did you have with it. This can tell a lot but sometimes it is just hard to know. Typically the starch group and of course sweets is what gets most people.When we go to long with out eating our body kicks in an gives us energy from stored sugars in the body and we can have a higher number instead of a lower one, so it is important to eat regular spaced healthy meals.Exercise is a great benefit to keeping those number lower to, and some days it just dont seem to make sense what you do. Pain, illness and stress also effect these numbers somewhat. The American Diabetic association is a great place to get reliable information from. If you are getting high readings regardless of the why the body is sending you a warning that the pancreas is not working as effectively as it has in the past, an now is the time to make those changes. I hope this has helped. Is hard to answer like this, I am a diabetic educator so I see this a lot.

    • I’d love to share resources if you’ve found anything. My situation seems similar. I eat low carb, do hot yoga and intense workouts (one or the other every day). My numbers are really similar to yours, though I rarely get a low post-prandial unless I eat too many carbs – like my pancreas is giving extra effort since it doesn’t usually have that many carbs to contend with usually. Western doctors can’t figure it out and don’t think I have a problem since A1C is under 6… even though I eat so little carbs! So frustrating that they don’t get it! I’ve spent too much money on functional medicine and just want to keep trying my own thing. I do think Berberine and black seed oil taken at bedtime, along with some protein, helps a bit.

  9. 57yrs, was a gestational diabetic, I have been on 2000mg metaphormin since 2009, I had taken the 3 hrs glucose test several time and failed miserably.My morning readings r great, My 2 hr post reading have and are always high (155-255)….however my A1C is 5.6, my weight is good….I have been using a short term insulin for my meals-Asparta, works well. My Dr. wants to take my insulin away, due to my normal A1C #’s….Your thoughts?

    • I don’t know what your carbs/insulin units ratio is but seems to me reducing the amount of insulin you use would be better than stopping altogether cold-turkey. If your A1C can be controlled with less artificial insulin let your body supply what its meant to supply.

  10. Hi, hope you are doing well. I was hoping you could help me resolve a dilemma. My morning blood glucose levels range between 95 and 99. However, after constantly monitoring the levels at 1, 2 and 3 hour intervals respectively, I have concluded them to be normal. After about 2.5 hours of a meal, my levels range from 85 to 90. Also, my fasting levels (8 hours without a meal) are always under 90 at night but they are close to 100 in the morning. Could you please shed light on this? I shall be ever so grateful.

  11. Hi Chris,

    I have observed that when having a meal that contains both fats and carbs my blood glucose takes longer to rise, and it takes longer to go back to base. So the graph/curve of the spike takes longer to complete: in my case it takes about 1.5 to 2 hours to reach a pick of 160 when having both carbs and fats, then it takes another 2 hours to go back to base.
    when having carbs without fats the spike is lesser and going back to base is shorter (the same amount of carbs will not get me to the 160 peak but more like 140). Also, I know for sure that I am not insulin resistant (on the contrary, I am very insulin sensitive).

    My questions:
    – Your recommendations for doing the OGTT are based on consuming only carbs. But what would be the recommendations (numbers) for a healthy individual when fats are consumed as well with the carbs. Would they still remain 140 after first hour, 120 after two hours etc. Fats definitely change the curve right?
    – Is there a natural way to “prime” insulin (maybe through eating some food that spikes insulin but not glucose, or supplement), before consuming carbs such that the pick will be lower? … because in the case of being insulin sensitive and yet experiencing this high pick it seems that the response mechanism of the pancreas is delayed in my case? Is there a variety in the response time among people and therefore that would be normal still? (I have tested negative for type-1 and type-1.5, that is no auto immunity against pancreas)

    • An OGTT is a diagnostic test, and as such in order for the results to be relevant one performs the test as prescribed. Consuming fats anytime during the test would totally invalidate the results. There is a hormone that is sensitive to fats consumed which slows the progression of what is eaten from the stomach to the small intestine; fats, carbohydrates, proteins and indigestibles, the whole shebang. So, that fats plus carbs takes longer than carbs alone to peak and then return is entirely normal. There is some variety from person to person how quickly BG is metabolized, but mostly what you have observed is a function of WHAT is eaten.
      As far as the magnitude of your peak that is mostly a result of how many carbs you consume and how quickly, but is also affected by how you collect your data. Do you check your BG every 30 seconds for the whole two hours? No? You may be missing your peak value by virtue of timing. Also consider that a Glucose meter is considered “accurate” even when yielding a measurement 15% off the true value. With this in mind, 140=160 under certain circumstances.
      Your body’s release of insulin is in direct proportion to your blood’s glucose level (unless you’re completely T1). Therefore there is no way to “prime” your blood with insulin other than via injection. (The body’s insulin reaction is pretty rapid anyway.) The best way to lower your BG peaks, if that is your goal, is to EAT MORE SLOWLY, and to consume fats with your carbohydrates. Diabetics are taught to not just eat an apple, but eat an apple with some peanut butter.

  12. Chris, you wrote: “One caveat here is that very low-carb diets will produce elevated fasting blood glucose levels. Why? Because low-carb diets induce insulin resistance. Restricting carbohydrates produces a natural drop in insulin levels, which in turn activates hormone sensitive lipase….”
    Maybe because the article is so old the above wrong information is iin it still ? The reality, as Jason Fung has explained well it is that when insulin drops liver glycogen is first released. If one was diabetic-2 or pre-diabetic-2 before one went on low carb the liver is larger and fattier than normal. That means longer time with higher than normal fasting blood sugar. There are two ways to quench this smouldering fire: Several weeks on ketogenic calorie restricted diet. Calorie restriction is a must, as the energy in the liver must be used up. On a ketogenic diet it has been proven time after time that calorie restriction does not reduce metabolism as long as there is minimum body fat left, which means a gradual restoration of perfectly healthy insulin levels can be attained without freezing, which means when the targets in FBG, waist measure (and body weight!) are met, all is stable. A faster variant is to combine fasting 3-5 days in a row which brings insulin down much quicker. The drawback here is that FBG tends to go up as long as the liver isn’t “empty” of glycogen or fat . But after a few weeks like that the liver is restored! (Eating carbs at night is counter productive as it raises insulin and only gives a temporary lower FBG as insulin stays high preventing glucose from liver to flood the system.) Lowering insulin is the safe way to empty liver sugar stores but it means a temporary flooding with glucose, until the liver store is empty. Clearly a finite process, but after 2 days without lowered FBG many believe that the theories put forward above are right. I have however tested Jason Fung’s ideas on myself, and they worked! I lost 9 kgs (20 lbs) over 3 weeks fasting 5 dayas and eating 2 days. Energy and body temperature great all the time, ended about 4 months ago. FBG came down to 3.1 for me at the end of the 3rd day. Since I at the same time was full of energy my “hypoglycemia” was accompanied by ketones, providing that extra energy. Today my FBG is 80 (4.4) eating a low carb diet, nearly ketogenic! My waist also reduced significantly during the IF ,and it stayed down! I am amazed that it was possible also for a rather old guy like me, 70, to remove that stubborn bump, often through sad experiences named the widow-maker.

  13. There’s something a bit funny phrasing-wise in the article. It says “continuous glucose monitoring studies suggest that the ADA levels are far too high” which makes it sound like you’re measuring ADA levels in the blood. Maybe the ADA levels ARE too high. =D! Kidding aside, thanks Chris. Long time reader.

  14. Your 2nd to last paragraph has left me wanting more information and it seems to be where most articles leave off and I have been searching for MONTHS the answer to this question. I would love (NEED!) to hear more! Here’s the paragraph that left me wanting more info and I will explain with my own situation following.
    *If you’re following a low-carb diet, fasting blood sugars in the 90s and even low 100s may not be a problem, provided your A1c and post-meal blood sugars are within the normal range.

    I have been doing low carb (Keto) hardcore for 8 months, no cheats and staying at 20g of carbs or less with an occasional 40g day. I noticed at 8 weeks into the diet that I was not losing weight, knew there was a medical hangup. I decided to test my blood sugar levels. All post meal #’s were excellent (Under 120, usually averaging around 108) but noticed that my fasting blood glucose numbers ranged anywhere from 123 – 163. So discussed this with Dr. Wanted to put me on Metformin and I asked for her to allow me to continue keto to the 6 month mark and to see if it would change my FBG. I lowered my protein intake (worried that maybe too much protein was causing a glucose excess?) and I began to slowly lose weight from my stall. But I stalled again and again. in 8 months, my weight loss has been 35lbs with no cheats and I added Intermittent Fasting to my regimin. So I know that my FBG has to be the culprit behind my stalls. At the 6 month mark, I agreed to Metformin as the numbers were not changing(Sigh – I did not want to, but something needed to give). I had blood work done, thyroid was fine, cortisol was fine, my vitamin levels fine and my A1c was at 5.7. I was prescribed 500mg of Met at night with dinner. At first, it did not lower my FBG, it stayed in the 140’s, with occasional dips into the 130’s. And finally after 3 weeks, I added Turmeric + Cinnamon to my nightly dose of Met. This finally started bringing my numbers down. Mostly in the 115 range with an occasional number around 108. So I am seeing progress. BUT your paragraph, that I quoted above, says that if you are doing LCHF, then these numbers may not be a problem (I know my numbers above the low 100’s are a problem, but what did you mean, that it may not be a problem in the low 100’s if you are LCHF? Can you send me links to read? I’m battling something fierce here and I can’t figure it out. Something is hindering my weightloss in a big way and I know that it has to do with high fasting glucose and while I am finally getting them to come down, I feel like I am still missing something (and why do I feel like giving into Metformin is going to create a larger problem for me?). I’m desperate to lose weight. It’s coming off painfully slow (I’m 44 but no where near menopause yet, according to OB). I know that I am not eating things I shouldn’t be, I have re-evaluated carb creep, studied Jason Fung, hung on every word of Eric Westman, yet still, I am struggling to get this fat loss moving! I feel like I am definitely fat adapted because I’m not hungry, I can go hours and hours without eating, all of the tale tale signs of ketosis are evident. What can I do to get over this huge hump of extreme insulin resistance and start losing this weight once and for all? I cut out dairy and still no improvement. So I added it back in. I am missing something somewhere. I am grateful that I have lost 35lbs (and inches too!) and I know I shouldn’t be ruled by the scale, but I feel like I should have lost more inches by now and more weight. Any insight would be so appreciated by me! IF I eat breakfast (I usually try to fast) it’s 2 or 3 eggs with spinach scrambled in or green peppers / onions (keeping an eye on carb count), lunch is usually a salad with meat and home made ranch dressing and dinner is always a protein with a veggie (Cauliflower, greenbeans, spinach, broccoli, yellow squash, zucchini – something along those lines). I rarely ever do any crazy recipe baking and prefer to keep it simple, but occasionally, in desperate times, i will make a mug cake with almond flour or make jello fluff, but it’s pretty rare.

    • Oh and I watch my macros carefully. I stay around 50-60g of protein per day and maybe around 100g of fat per day. I’ve played with the fat macro on multiple occasions for weeks at a time to see if It made a difference, I will go lower (80g or higher and stick to those for a few weeks to see if there is a trend up or down, but nothing seems to make a difference, fat wise. I am usually right around 100g per day, give or take 10 grams either way. I’m at 20g of carbs. I’ve tried upping them to 30-40 with no change (I stall out here) and I have actually done just a few days with 10g of carbs or less, no change or even several days at 0g, but I miss veggies too much and 0g seemed to cause more issues than it’s worth (going back to the eating too much protein causes excess glucose theory???)

    • Do you monitor with ketone test strips? Dr. Robert Atkins writes about stalling on a carb regulated diet. Thyroid among other things, but you said yours was fine. I’d bet your high FBG isn’t CAUSING your slow weight loss; I think they’re both SYMPTOMS of the same thing, whatever that might be.

    • I have also done low carb and lost 68lb but put it back on over a couple of years.
      I have now lost 75lb on the Blood Sugar Diet and watched my blood sugar A1c drop from 11 to 5. I was on 2000mg of metformin a day and that has also dropped to 500mg but I am likely to come off it altogether at my next review, as in my opinion I have successfully reversed my diabetes.
      The reason I am replying to your comment is that on both diets I have also ‘stuck’ at regular intervals and the only thing that helped on these occasions was to INCREASE carbs until the weight loss started again – sometimes just one carb meal would be enough, other times a couple of days, but every time I stalled, this worked.
      A day ago, I had bread three times in one day and was convinced I had put weight on, only to find I had lost another couple of pounds. I don’t know why it works, but it works!

      • Tricking your body and taking it out of keytosis from starving it from sugar is the key. The body will naturally return it self to normal and then after a few days of cheating on your low carb diet start the process all over with the carb reduction and your body will again start to burn off fat again. So it’s good to cheat and add carbs for a few days when you can’t seem to loose any more. Your body will tend to stop loosing the fat as a defense mechanism to save its self from starvation when in keytosis. When too much weight comes off all at once your body will again try to save its self and eventually start consuming muscle to feed it.

    • Jennifer P, It sounds like you are doing great with your diet. Are you exercising at all? Building muscle may add pounds, but you still lose inches. Building muscle is also great because it helps to change your metabolism. (I’m talking about moderate exercise and muscle building, not becoming a professional body builder.) My own personal goal is 30 minutes of moderate exercise a day, which may include walking, riding my bike, using the elliptical machine, nautilus weights, and yoga. (I don’t do all of them every day.)

    • I suggest that you read How Not to Die and follow a whole food plant based diet as Dr Gregor suggests as closely as possible. See how that works for your overal health and not just the issue expressed above. It sounds like it shouldn’t be too hard for you being that you eat better than the average person.

    • Thanks for sharing. I struggle with the same problems. I can’t get the last 10 pounds off. I wonder if having my FBG always over 100 stops my ability to be in ketosis. I’m a try adding a higher carb Day here and there. Will also try adding cinnamon and tumeric at night. I hate that it has to be such a pain. I guess it’s because we are so good at storing fat for survival!

  15. I’m hypothyroid and have been on thyroid medication for about 15 years. I’ve gained a considerable amount of weight in the last few years even though I eat a healthy diet and exercise. My endo has been checking my A1c for the last 3 years and it’s gone from 5.7, back down, and then 5.8 and now up to 5.9 recently. My recent fasting blood sugar was 77. She wants me to start s low dose of metformin. I’m confused about the higher a1c and lower fasting blood sugar. Thoughts?

    • An A1c of 5.8 would indicate that your AVERAGE blood glucose is close to 120mg/dl. If your FBG is 77 then your non-fasting levels are probably well above 160 (maybe even higher than 200). A “normal” person should spend very little time (non-fasting) above 140. That’s probably why she’s prescribed Metformin. 77 is surprisingly for an A1c of 5.8, but if your FBG was say 100 with an A1c of 5.8% she might not have prescribed the Metformin. You should ask her. You may not be prediabetic and as the author writes there may be better ways for finding out what is going on than having an OGGT, but you may want to get a glucose meter to test often at home and you may want to educate yourself on Insulin Resistance.

      • Actually, my a1c this time was 5.9 and my FBG was 77. It’s strange. I’ll look back and see what my FBG was those other times that my A1c was in the pre diabetic range and post.

        • Sound like hypoglycemic swing for you. You probably drank black coffee before the blood test. Don’t drink anything except plain room temperature water, and make sure you didn’t eat and didn’t drink anything except water for 12 or more hours.

        • Remember FBG is the least accurate marker for disglycemia because it is only a snapshot, i.e. it is not time-averaged, and it is more easily influenced by other factors including how active you are just minutes before the test. A1c=5.9% correlates to an Average BG of 123mg/dl.

    • My a1c was 6.5 and I was put on Metforman… It caused me to have ketoacidosis because I couldn’t eat. My fasting blood sugar I stopped taking it for 4 days because I was admitted to the hospital. My A1c went from 6.5 to 6.1 in 7 days. While in the hospital my fasting blood sugar was between 77 and 89. I got one reading of 110 because my nurse made me eat graham crackers and drink apple juice before bed. Since I been home, the my blood sugar stayed between 88 and 96. I ate pineapple before bed and that’s probably why I got 96. Idk… I think I’m pre-diabetic, but I don’t want to chance anything. I constantly check my BG because this is a wake up call.

  16. Hello,

    Fasting blood glucose is 176
    A1C is 5.2%

    Similar results 4 months ago

    Not anemic

    White male 70 years old

    My Dr. says since 5.2% is in target range – just ignore the elevated glucose number

    Any advice –

    Thank you!

    • Did you eat ANYTHING in the two hours previous to the 176 reading? No? Get ahold of a glucose meter and check your fasting BG again.

  17. Hi Chris, I had gestational diabetes for my pregnancy, before I got pregnancy, I had a test on my A1C and was 5.3. I had excellent control with my GD and my BG has always been under 7. However, I just had the baby 2 months ago, and I have been testing my sugar level after meals, fasting has never been a problem, 2 hours occasionally goes high after high carb meals. But sometimes it was like two hour BG spike like 9 or 10, then 2.5 hours back to under 6..almost seems like there is a delay in my insulin…I also started to test my one hour BG, and it has been higher than 7.8, normally around 8.4. Shall I get concerned?

    • I’m in a very similar situation. I was dx with GD at 26 weeks and very easily diet controlled. Rarely had a number above 140 (1 hour tester) and when I did it always was below 120 2 hours post meal. I’m 2 months postpartum and I’ve been spot checking and my 2 hour number seems to be lagging. I had a hefty pizza meal with close to 100g of carbs and my 1 hour number was 130 and my 2 hour number was 132! My 3 hour number was 110 when I checked out of curiosity.
      Tonight we had a quick fast food meal between running errands and again it was close to 100g of carbs. We took a 30 min walk when we got home and I was so happy to see my 1 hour number at 115. Checked the 2 hour number and it was 143!! I don’t get this!!!

  18. This is a fabulous article which outlines considering patients individuality in context to disease prevention and managementbrather than looking just at lab testing alone, misleading many doctors to misinterpret the numbers and not serve their patients well, again the limitations of evidence-based medicine in clinical practice

    • I couldn’t agree more. My doctor just sent me for an A1C test and I have diagnosed anemia. My 12 hour fasting blood sugar checks (at home) are never below 150 and run as high as 175….for 7 straight days. Yet, my body craves sugar.