Why your “normal” blood sugar isn’t normal (Part 2)

November 18, 2010 in Diabesity | 87 comments

fat_normalIn 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.

Marker Normal Pre-diabetes Diabetes
Fasting blood glucose (mg/dL) <99 100-125 >126
OGGT / post-meal (mg/dL after 2 hours) <140 140-199 >200
Hemoglobin A1c (%) <6 6-6.4 >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 diabetes and cardiovascular disease.

Fasting blood sugar

According to continuous glucose monitoring studies of healthy people, a normal fasting blood sugar is 83 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’s not. A study in Diabetes Care showed that the risk of heart disease increases in a linear fashion as FBG rises above 83 mg/dL. Another study in the same journal showed similar results.

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.

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.

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%

And 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.

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 every 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.

This study showed that even after a high-carb meal, normal people’s blood sugar rises to about 125 mg/dL for a brief period, with the peak blood sugar being measured at 45 minutes after eating, and then drops back under 100 mg/dL by the two hour mark.

Another continuous glucose monitoring study confirmed these results. 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.

Even the American Association of Clinical Endocrinologists is now recommending that post-meal blood sugars never be allowed to rise above 140 mg/dL. Unfortunately, less informed groups like the ADA haven’t caught up with the science.

The consequences of this are severe. Nerve damage occurs as blood sugar rises above 140 mg/dL. Prolonged exposure to blood sugars above 140 mg/dL causes irreversible beta cell loss (the beta cells produce insulin). 1 in 2 “pre-diabetics” get retinopathy, a 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:

Marker Normal Pre-diabetes Diabetes
Fasting blood glucose (mg/dL) <99 100-125 >126
OGGT / post-meal (mg/dL after 2 hours) <140 140-199 >200
Hemoglobin A1c (%) <6 6-6.4 >6.4

But as we’ve seen in this article, these levels are only normal if you think increased risk of diabetes, heart disease, cancer and other serious complications is normal. Just because these conditions are common, doesn’t mean they’re normal.

If you’re interested in health and longevity – instead of just slowing the onset of serious disease by a few years – you’d be well advised to shoot for these targets instead:

Marker Ideal
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 very reliable for predicting diabetes or CVD risk. Post-meal blood sugars are by far the most 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.


Bridwell CPhT November 20, 2010 at 12:46 am

K… Don’t know where or how old this info is. I’m work in pharmacy and just took a CEU on Diabetes that the info is good on for the next two yrs. Normal is 70-130 and a1c of 7%. So… wondering what source is being used for these statistics. You can view mine at wwww.powerpak.com look for the CEU on Diabetes.

Chris Kresser November 20, 2010 at 8:59 am

Did you read the article? The whole point is that the mainstream targets you learned in your CEU class are not supported by the scientific literature. An A1c of 7% maps to an average blood sugar of 172 mg/dL. Studies clearly show blood sugar that high dramatically increases the risk of cardiovascular disease and diabetic complications. The same is true for a fasting blood sugar above 95 mg/dL and 2-hour post-meal / OGTT readings above 140 mg/dL.

Lacie November 20, 2010 at 10:51 am

Chris, this is some of your best work. My BF and I are two months into a low carb diet and my blood sugar has stabilized, but he still has extreme hunger between meals and has to eat 4x a day. Can’t wait for your third installment where you show how to check blood sugar between meals–I suspect he has some insulin issues that I don’t have.

Chris Kresser November 20, 2010 at 11:15 am

Thanks, Lacie. As for your BF, it could be a reactive hypoglycemia pattern, where the insulin surge after meals is too high, and he goes into a hypoglycemic state (which produces the extreme hunger). Cortisol dysregulation is often involved in this situation.

Jamie November 20, 2010 at 11:26 am

Thank you so much for these incredibly well-written articles.

Lynn November 20, 2010 at 4:33 pm

Great article. You mention that FBG can be elevated on a low carb diet. What do you consider a low carb diet to be in terms of grams? Anything under 150g a day or do you mean a keto diet?

Chris Kresser November 20, 2010 at 4:35 pm

Lynn: I think there’s wiggle room here, and it depends somewhat on the metabolic function of the individual. But I don’t consider 150g to be low-carb. I’d say that’s more in the realm of “moderate”. I’m thinking more like 100g and below.

Lynn November 20, 2010 at 5:25 pm

I used to think LC was under 100 carbs also, but apparently the strict definition of LC is less than 130: http://livinlavidalowcarb.com/blog/?p=6648.

My BS is better on 120-150 carbs than it was on VLC, but I am wondering why my FBS is not ideal still,; though my PP numbers are where they need to be.

Any thoughts?

Chris Kresser November 20, 2010 at 6:00 pm

If you’re PP & A1c are in the normal range, I wouldn’t worry about a mildly elevated FBG.

Lynn November 20, 2010 at 6:06 pm

Any other thoughts on correcting IR? I read all your posts and I watch my carbs, eat a strict gluten free diet, limit vegtable oils (I have recently gone further and embraced an extremly low PUFA diet, so no more bacon etc. for me) and get good sleep. I also take metformin and natural thyroid.

Despite all of this, my insulin is never below the magic 10. Any ideas on what I can do?

Chris Kresser November 20, 2010 at 6:30 pm

There are a number of botanicals and nutrients that can help improve insulin sensitivity. You could also try intermittent fasting, provided your cortisol levels are not out of whack.

Chris Kresser November 20, 2010 at 6:34 pm

Could also try high intensity strength training, to make sure you’re really depleting muscle and liver glycogen occasionally. Something like Body By Science.

Julie November 21, 2010 at 7:29 am

Chris: if, as you state, “low-carb diets induce insulin resistance,” why isnt it a cause for concern? I went low carb some time ago, no processed foods or bad oils, lost 20 lbs, do regular strength and resistance training, A1c 5.3, post-prandials <120, usually <100, very low BMI and BFP.

But now my FBG levels are as high as 125! (Used to be 87) I guess I don't get the logic behind the assurances that a low-carb diet "may not be a cause for concern" when in the same article you quote studies showing diabetes risk in people with FBG levels above 95. Type II diabetes runs in my family, including those who are not overweight. Does someone like me need to be concerned? What are the botanicals and nutrients you refer to that can improve insulin sensitivity?

Chris Kresser November 21, 2010 at 9:13 am


I didn’t mean to imply that it is never a concern; just that it may not be a concern. It depends a lot on what your post-meal and A1c levels are. For example, if you wake up at 105 mg/dL but drop down in the 80s soon after, and stay between 80-120 for the rest of the day, I may not be concerned (I’d also have to consider your symptoms, micronutrient status and other clinical variables).

However, if you wake up at 105, never drop below that level, and experience post-meal BS of above 140, then I’d be concerned. Those are two totally different patterns.

The studies that were done showing FBG >95 causing harm were likely done in people eating the Standard American Diet (for the most part). I suspect had the researchers tested their post-meal blood sugars, they would have been high. So I’m not sure we can extrapolate those results to someone eating a low-carb diet. I believe there are some studies showing that higher FBG with normal post-meal BG doesn’t predict future diabetes, but the opposite is not true, i.e. studies show that you can have a normal FBG, but if you have elevated post-meal BG you’re still at risk.

This is a complicated topic and several variables are involved. Check out an interesting article and discussion in progress at Stephan Guyenet’s blog. Make sure to read the comments.

Chris Kresser November 21, 2010 at 9:19 am

Julie: also note that some people actually experience better blood sugar control on a moderate carb. diet than a low-carb diet. I suspect this is related to the phenomenon I described above, where introducing some carbohydrate gets the body accustomed to burning it again, and probably prevents cortisol and/or epinephrine from getting involved.

Michael Barker November 21, 2010 at 5:26 pm


Thank you for doing this topic. I write a diabetes blog and I try not to club the ADA all the time but those guidelines always seem to pop up. They are a major problem because they give people a since of security that they shouldn’t have.

I was actually thinking about this just before I read your blog. I’m a type 2 ketosis prone diabetic with a family history of diabetes and because of this I view the ADA guidelines as nearly tragic for people like me. I’ve come to a decision that I’m going to tell people in my family what are the real guidelines for diabetes. Basically, I’m taking the FBS ADA guidelines and using them for everything. Less than 100 is normal. 100 to 120 is the prediabetic range and above 120 is diabetic. I know that sounds pretty drastic for postprandials and the like but I would rather my children and grandchildren have a chance for a healthy future.

I wrote a long blog on hemoglobin and A1c and put up charts of the people who are most likely to have these sorts of problem, whether they are diabetic or not. Interestingly enough, this seems to match up with peoples that live where Malaria or Malaria like diseases occur.

Michael Barker November 21, 2010 at 5:46 pm


Just read your replies on Whole Health. Here’s something to test on people you know who spike easily. Give them a NSAID for two or three days. If their blood sugars cease to spike then it might be a glucose desensitization issue. The has to do with inhibiting COX-2 and PGE 2. I’m reporting on this on my blog.

Chris Kresser November 21, 2010 at 8:11 pm

Thanks for your input, Micheal. I’ll check out that post.

Jay November 22, 2010 at 12:02 pm

Another great article, Chris. I’m puzzled by my FBS being around 95-99 but frequently my 2 hr post prandial will be below 90. Shouldn’t the FBS come in lower? Is this a morning cortisol stress response?

Chris Kresser November 22, 2010 at 12:35 pm

Not necessarily. It’s common for LC folks to have FBG in that range. Presuming your A1c and post-meal numbers are good (which it sounds like they are), I probably wouldn’t worry about it. As your body becomes accustomed to burning fat for fuel, insulin sensitivity decreases. This can cause a “dawn effect” where FBG is higher than you’d expect it to be.

Some people find that adding a moderate amount of carbs in the form of safe starch, for example, helps normalize their blood sugar.

Mark T November 22, 2010 at 5:49 pm

This is very interesting. I recently started eating fairly low carb, trying to follow the guidelines of the Perfect Health Diet (thanks for reviewing that, great book!) Then I got a FBG among other screening tests, because suddenly three elderly members of my family have been stricken by cardiovascular disease. The FBG was 110 mg/dL, causing me to investigate and freak out. Using a cheap glucometer I found evidence of the “dawn phenomenon” (83 mg/dL fasting usually, but 95-100 in the morning, have not repeated the 110 lab value). More shocking, I ate 8 oz of potato and it spiked my BG up to 237, down to 169 at 2 hrs, then mildly hyperglycemic (70 mg/dL) for a couple of hours. Response to a normal low-carb dinner was pretty benign. I did not mention the potato test to my doctor, who is unconcerned. I don’t know what to think. Looking forward to your next post!

Chris Kresser November 22, 2010 at 6:06 pm

Mark: that kind of pattern is consistent with reactive hypoglycemia, which is often the earliest stage of the progression towards diabetes. I’m glad to hear you’re now eating low-carb, as BG of 237 after a potato is definitely cause for concern.

If you’ve been LC for some time, it’s possible your body has adapted to burning fat and that’s why your glucose tolerance is impaired. The only way to find out would be to eat a higher amount of carbs over a 3-day period. If your blood sugars start to come down, it suggests you are adapted to fat burning but don’t have metabolic damage. If your BG stays high, it suggests you’ve got some metabolic damage that needs to be addressed.

Mark T November 22, 2010 at 6:22 pm

Thanks for your thoughts, Chris. I may give your carb-up test a try. I think I may have always had this response to carbs, at least the reactive hypoglycemia part. I get a little sleepy after an unusually large meal, which in the past has always meant a meal with plenty of carbs. I used to think everyone reacted that way. Maybe my mom’s side of the family (where the CVD is occurring) all have this too, staying mild enough to not trigger investigation for diabetes, but causing damage. My wife (a doctor) and a friend (a nurse) both are very skeptical I could be T2 diabetic, perhaps because I am not overweight and seem healthy. But BG of 237 is not healthy! Do you think I should get a HbA1c test to assess the current damage level?

Chris Kresser November 22, 2010 at 6:28 pm

Mark: if you’ve always had that response, and if you feel sleepy after carby meals, I wouldn’t recommend the carb re-feeding. That’s indicative of a metabolic issue, and it’s probably not wise to potentially push your blood sugars above 200 in light of this.

Mark T November 22, 2010 at 7:36 pm

Chris, thanks again for your advice. So do you think I should eat a low-carb diet, monitor BG to keep it under some level (140?), occasionally check HbA1c, and continue to exercise regularly? Should this prevent further trouble? Can the metabolic problem be improved, or just worked around carefully?

Chris Kresser November 22, 2010 at 8:45 pm

Usually it can be addressed. It depends on what’s causing the problem in the first place. For example, if it’s “lifestyle”-related (i.e. diet, stress, sleep, etc.) and it’s early enough in the process it should be possible to completely restore healthy metabolic function. If it’s autoimmune, or has progressed long enough to where beta cells have been destroyed, then insulin signaling may be permanently damaged. In that case it would be a case of improving insulin sensitivity and glucose utilization to the fullest possible extent, and making dietary and lifestyle changes to prevent further damage. Feel free to check out my professional site and book a free 15-minute consultation if you’re interested in pursuing this further.

Mark T November 22, 2010 at 8:52 pm

Thanks, Chris, that’s encouraging. I’ll check out your site. I have learned a lot from your blog.

Angela November 23, 2010 at 6:51 am

Hi Chris
Thank you for your blog. It comes at just the right time. For the second time this year, my A1c was 6.0, so my doctor now wants me to do a 3 hour glucose test but I’ve been very weary of doing this (especially since my fasting glucose is 78). Your post-meal monitoring makes more sense to me. I know that I should be concerned that I might be pre-diabetic (even though I’m skinny). I’m looking forward to learning how to do this. Also, what kind of exercise do you feel is best to keep blood sugar levels down?

Chris Kresser November 23, 2010 at 8:31 am


I think high intensity strength training is the best type of exercise for restoring and maintaining insulin sensitivity and glucose utilization. I’ll write an article about this soon.

Angela November 23, 2010 at 10:10 am

Great! Thank you.

Susan November 23, 2010 at 4:59 pm

Hi Chris,

What a timely post. I have been low carbing at about 50 carbs average per day for the past 21 months. I don’t normally check my BS but, was curious when I did do a FBS to find my morning level at 115. Then, I read about the phenomenon of LCers having high morning levels and felt a little more reassured. I have been checking my post-meal levels for the past few days and I am pretty confused. One hour after eating my level will be around 101 and two hours later it will be at 113. Even after three hours it is still going up, say to 119. I will have had nothing to eat or drink during this time. Is, perhaps, my meter not working correctly? Shouldn’t my levels be decreasing after that first hour postprandial?

Chris Kresser November 23, 2010 at 5:11 pm

I’ve seen patterns like that in my practice and it’s pretty typical of cortisol dysregulation. That may be why your fasting blood sugar is elevated as well. The normal pattern would be a blood sugar peak 45 minutes after eating, returning to baseline by 2 hours. Something is raising your blood sugar in a fasted state, and cortisol (and/or glucagon) are the likely culprits.

Jo November 24, 2010 at 6:38 am

Hi Chris, firstly thanks for your posts, I’ve read them all and it is helping me in my plans to manage some diagnosed and undiagnosed problems. I want to monitor my blood glucose levels as they have been creeping up in FB tests. I had an OGTT, came in under range, but not a lot. I live in Australia, is there any chance you can convert the lab values you recommend into the common ranges we have here? Our fasting levels (IMVS labs) are “normal” at 4 to 6 mmol/L, and two hours post OGTT <7.8 mmol/L


lynn November 24, 2010 at 7:05 am

Hi Jo

To convert US units to mmol/L, simply divide by 18. So, a US unit of 90 divided by 18 = 5.0 in the UK, Ireland and Australia units. To convert an Aussie unit of 5.0; multiply by 18 = 90.

My blood glucose monitor is in the MMMOL/L units, but since all literature I read is in US units, I convert instantly and focus on the US number.

simona November 24, 2010 at 7:08 am

Hi Chris,
I have two questions. You have been very kind and answered many already. I hope it’s not too much to ask.
Regarding that effect of raised post prandial glucose after reintroducing carbs, I remember there was a day when I had two very small boiled potatoes in a salad with protein and fat for lunch and I felt very sleepy after a while. The idea was to help revv up my metabolism (a la Matt Stone) I got a bit scared but now (after reading Stephan and you) I understand that it takes time for the body to adapt. However, my body shows signs of previous hyperinsulinemia, like skin tags, small acanthosis nigricans, I was wondering how can I know if it’s still a problem after two years of low-carbing and losing weight. Is insulin resistance not the cause? Would high-cortisol (chronic stress) cause high insulin too and then high androgens (which is also a problem)?
My mother has diabetes type 2 for the last 25 years or so. She has had severe hypos and some of them happen at night. What could be the reason for a hypo at 2-3 am when there isn’t much basal insulin left (taken at 8 a) Is the glucagon/epinephrine release necessary to get glycogen out of liver not working?
Four questions, not two.

Thank you.

Jo November 24, 2010 at 7:16 am

Thanks Lynn, these conditions have killed my brain! Am looking forward to the next article, I’ll be picking up a monitor shortly.

lynn November 24, 2010 at 7:32 am


If you want to try Matt Stone’s protocol, I would suggest you pick up his free RRARF eBook. His program is not just about increasing carbs; it is also very low fructose and very low in PUFA’s. There are other parts of it too.

Also, feel free to email him. He is very responsive to emails.

I have tried everything to get my insulin down and eight years of low carbing has done nada. So, I am trying the Ray Peat program. It is high carb too; but is extremely stringent re: PUFA, meat etc. The only thing Stone and Peat have in common with the SAD is that they both include carbs. However, thereoin they are world’s apart. Just raising carbs ala SAD won’t help at all. The biggest misconception re: Stone is that he advocates junk food and junk carbs. He does not. :)

lynn November 24, 2010 at 7:32 am

Also Jo, what conditions do you have?

simona November 24, 2010 at 8:42 am

Thanks Lynn,
I have his free ebook. I have been low carb (50 g veg carbs) low Pufa (o6 only from meat, olive oil and eggs, o3 about 2 grams for a while, stopped it) and low sugar, low fruit, no wheat, no pulses for more than two years (aug 2008). Minimal supps. I was only increasing potatoes and sweet potatoes (see also Paul Jaminet’s blog) for the last month. I should be doing better, but still struggling with gum disease/infections, even worse than a year ago, acne, hairloss, weight loss stall. Wide ranging hormonal issues, I think, cortisol affecting inflammation, underlying androgen (5 alpha reductase) problems due to possibly inherited insulin signalling problems. Just guessing here, trying to make sense of it. Couldn’t get a clear PCOS diagnosis in the last 10 years I’m suffering of these symptoms. More recently low T3 shows the metabolism slowed down, the cause of which is not clear.

Chris Kresser November 24, 2010 at 9:04 am


High cortisol can cause insulin resistance, and vice versa. Low cortisol can cause hypos during the night. Insulin upregulates 17-20 lyase in women, which converts estrogen to testosterone and causes androgen dominance.

Unfortunately this stuff is very complex and it’s impossible for me to say more without knowing the particulars of your case. There’s no one-size fits all approach. Over-feeding may work in some people whose metabolic function is still relatively intact (though under-functioning), but I don’t believe it’s a good strategy across the board.

lynn November 24, 2010 at 9:23 am

Hi Simona

Peat is more gung ho anti PUFA’S than Stone is. A max of two eggs a day, olive oil only as a condiment and PUFA free meat such as beef and lamb.

When one increases carbs, it can expose hidden issues. Have you had a cortisol saliva test, a full thyroid panel (TSH, Free T4, and Free T3, anti-TPO, anti-TgAb and Reverse T3) and sex hormone panel done?

What are you basal temps? Temps during the day? Have you been to Stop The Thyroid Madness?

simona November 24, 2010 at 2:16 pm

Thanks Chris,


I saw a private endocrinologist in August and I think she asked for these tests, I had them done, but unfortunately I haven’t seen the results although I asked for them. She hasn’t said anything besides the fact that my LDL cholesterol is high. You would think she knows how to interpret them properly. She didn’t ask for a salivary cortisol test, so I’m just guessing there, from my experience. She doesn’t want to prescribe T3 as allegedly it is not licensed in Ireland.

simona November 24, 2010 at 2:22 pm

Oh, my basal temperature was ok when I had a look at it in the morning but I’m freezing all the time especially at night when I go to bed late, however, very often it’s around 14 C in the house. I checked that website too.

lynn November 24, 2010 at 2:24 pm

Hi Simona

Do you live in Ireland? Snap…..

It is ILLEGAL for her to withhold your test results. You need to speak to her secretary and demand them. If that fails, send a written letter to the records department, citing the Data Protection Act 1989. If nothing within a month, threaten them with legal action. Worked for me, because they knew that what they were doing was illegal.

T3 is available in Ireland yep. It’s not illegal.

simona November 24, 2010 at 5:41 pm

Oh, hello there. Thank you for reminding me about the Data Protection Act.

Jo November 24, 2010 at 7:12 pm

Lynn, I have Hashi’s, IBS, diagnosed with fibro, not yet convinced as I have chronically high inflammatory markers and signs of lupus without the ANA, kidneys at stage 2, elevated liver enzymes etc. I’ve just changed doctors and he is redoing all tests, so I haven’t modified my diet yet as I wanted to have these results without changing anything (to help eliminate factors that may be causing symptoms), then going to reexamine diet.

Susan November 25, 2010 at 12:53 am


Thank you so much for your response. Could a chronic aggravating pain, such as in a heel spur, possibly be responsible for the inbalance of cortisol and/or glucagon that causes the rise in blood sugar?

Once again, thank you.

Chris Kresser November 25, 2010 at 9:21 am

It would be the inflammation, more than the pain, that could contribute to cortisol dysregulation and blood sugar imbalance. But yes, the end result is the same.

Emily November 29, 2010 at 8:06 am

Hi Chris, thank you so much for your informative articles. I would be very interested to hear more of your thoughts on reactive hypoglycemia. I’ve had symptoms for as long as I can remember – eating moderate carb or low carb paleo helps a great deal. Not once in my life have I had a (fasting or otherwise) blood glucose reading over 100, though I haven’t done a careful two and three hour post-prandial test all together. Fasting is typically in the 70s, 1 hr after 50 g dextrose is low 80s, and other than that a few 90s over the years when not fasting. My symptoms of shakiness, sweating, and weakness occur approximately 2&1/2 hour after a high sugar meal (sugary cereal and skim milk, for example, back in the day, or a coke, which I haven’t had in 20 years due to this issue) and resolve with juice consumption or eating a piece of fruit. Once my blood glucose was checked then and it was high 60s, another time low 70s. (A aspartame diet drink while fasting, especially “cherry-flavored” will cause the same symptoms after 2 hours, though I haven’t checked the blood glucose then).

Anyway, your more detailed thoughts on the whole topic of reactive hypoglycemia would be most welcome. I seem to have found my curative diet in any event.

Chris Kresser November 29, 2010 at 9:45 am

Hi Emily,

With reactive hypoglycemia (RH), it’s typical to see a big spike in blood sugar after meals, followed by a hypo. In your case, I’m not seeing any spikes at all so I’d be more likely to call what you’re dealing with plain old hypoglycemia.

If you’ve been able to manage it with diet, that’s fantastic. Be aware that hypoglycemia is often associated with low cortisol levels or cortisol dysregulation, so that may be something you want to investigate.

Prof. Khalid November 30, 2010 at 9:46 pm

Dear Chris it is a great article. Two issues here (49y old)
1. My blood sugar after 2 hrs from normal meal is 100-120
However fasting is 110. I have low bg variance around 110 all the day.
2. My a1c is 6.5 and does not match with my average of 110

Chris Kresser December 1, 2010 at 9:04 am


What are your highest readings at 1-hour after meals? With an A1c of 6.5, and FBG of 110, it would appear you must be having some spikes somewhere throughout the day.

OTOH, A1c isn’t always accurate for a variety of reasons. You could try getting fructosamine tested to see how it compares.

Blood sugar regulation is complex, and individual. It’s hard for me to say more without doing a more extensive intake.

Michael Barker December 1, 2010 at 9:42 am


One thing I just thought about in relation to Khalid. Most of the world uses mmol/l for A1c. A 6.5 would translate into about a 5.5 mg/dl A1c which would be about the right number given his daily readings. He might just need to check the units.

Chris Kresser December 1, 2010 at 9:43 am

Good point, Michael. It would be so much easier if the U.S. caught up with everyone else in this regard.

Lila December 2, 2010 at 6:18 am

Recently diagnosed with insulin-dependent diabetes, and told to check BG only before meals and bedtime. These numbers were usually nothing to worry about.

But then I started post-prandial testing and was horrified to find out how worrying those were. I am on insulin but the ‘quick’-acting does absolutely nothing for the first two hours, then starts working about three hours later and is done in five hours. (A pattern verified by two weeks of testing hourly while awake, from which my fingers are just recovering, ouch.)

My FBG is normally in the 90s and each 10g of carb will raise by BG by about 50. Anything I eat will stick around until my insulin gets going 2-3 hours later, so it only takes a piddling 10g to put me in the >140 danger zone. If I do a 2-hour PP reading, it is *always* high but if at that point I add a small bolus, I’ll hypo about 3 hours later.

I have tried injecting further and further in advance of meals (up to 2 hours before eating, despite being warned not to do so by my diabetes team) but this hasn’t always worked as it is really hard to estimate how much you’re going to eat 2 hours later. Plus some days, the insulin does do what it says on the tin and leads to dangerous hypos (in the 20s).

Most days when the bolus is matched to my food, I’m back in normal range 5 hours later. Evidently I would prefer never to go above 140 but since it only takes 10g of carb to do that, that is easier said than done even on a low-carb diet. How much do I need to worry about those hours when my BG is above 140, as it almost always comes back down later?

My A1C is 5.9 which is a bit higher than what I would like; however my diabetes team doesn’t think it should go any lower.

Chris Kresser December 2, 2010 at 9:38 am

Lila: Have you read Dr. Bernstein’s “Diabetes Solution”? He’s T1 himself and it’s by far the best book I know of for T1s because he goes into great deal on how to use insulin properly with an LC diet. You might also want to check out bloodsugar101.com.

Lila December 2, 2010 at 10:13 am

Hi, I have read both cover to cover.

I’m just worried about constantly going over 140. My diabetes team isn’t too concerned about this because my BG is back in range by the next meal, and they say my A1C is fine and control is excellent. But from what I read from Jenny Ruhl and also from yourself (as in this article), BG shouldn’t go over 140 *ever* and I just wonder how concerned I should be as mine often does.

Chris Kresser December 2, 2010 at 12:05 pm


All of the research I’ve read, and people whose opinions I respect (like Jenny Ruhl & Dr. Bernstein), suggests that keeping blood sugar below 140 mg/dL is the best way to prevent future diabetic complications. I don’t have much experience with T1, so you might want to contact Jenny and see what she thinks. She’s usually pretty responsive.

Lila December 2, 2010 at 12:16 pm

Hi – despite living my life like a T1, I am officially a ‘ketosis prone type 2′. So I have the double joy of MDI/hypos _and_ the T2 baggage of ‘sloth and gluttony’ etc.

So does your advice on never going above 140 also apply to shooters like me?

Chris Kresser December 2, 2010 at 12:26 pm

I don’t see why it would be different, since the high blood sugar spikes are what cause the organ damage, complications and elevated CVD risk. Perhaps Micheal Barker will chime in here. He has a blog specifically for T2KPD.

Lila December 2, 2010 at 12:45 pm

Organ damage etc caused by spikes by themselves (with HBA1C below 6), or prolonged high levels (HBA1cs of 6.5 and above)?

I’m being told only the latter, but you seem to be saying *both*

With my deranged metabolism (slightly more deranged than your ‘average’ diabetic!), the only way I can never got above 140 is to never eat more than 10g of carb in one sitting.

Michael Barker December 2, 2010 at 1:32 pm

Yikes! Lila, I read your post and the first thing I thought was that you might be a KPD. I really try not to post too much on other’s blogs so I wanted to see what Chris had to say.

First of all, you’re one of the few people who I’ve heard of that have been officially dubbed “KPD”, that is a miracle in itself.

What made me think you were KPD? Your fast acting doesn’t work. Your body is producing counter regulatory hormones strong enough to counter a fast acting insulin. You go low hours after the fast acting is long gone, which means that your body is making insulin. You have a very strong response to carbs and that A1c is hanging near 6. Welcome to the “goofy” diabetes.

This is where KPD differs from regular type 2. Everything is still there and it’s working, it’s just all miss timed. It’s as if some control element is broken so the pieces no longer work together. The continual spikes, however, are going to keep messing up the system though.

I am willing to talk with you about this. You can find me on “Diabetes Forums” as Rekarb or on Tudiabetes with the same name.

reem December 9, 2010 at 4:57 am

I eat very low carb, except once a day i eat about 30-40g carbs in the form of white rice or sweet potato (this is to spare protein – i don’t want to have to eat an extra 50g protein a day just for gluconeogenesis).
My fasting BG is about 83 mg/dl , but i just checked my BG about an hour after I ate some white rice, and it was 147 mg/dl!!!
I’m pretty concerned about this! I’ve been eating this way for about 3 weeks now.(before, i was practically zero carb)..Will i always have peripheral insulin resistance, or will my body get used to this amount of carbs i eat per day?

Chris Kresser December 9, 2010 at 8:28 am


When your body has become accustomed to burning fat for fuel, it becomes naturally insulin resistant. However, this usually reverses after 3-4 days of a higher carb diet. I would keep testing and see if it doesn’t resolve.

It’s possible, however, that there are other mechanisms causing poor glucose tolerance that need to be explored. If your metabolism is damaged from previous poor eating habits or from autoimmune disease, your carbohydrate tolerance may remain low.

Another possibility, if you’re not doing this already, is to add high-intensity strength training to your regiment. This is an excellent way to restore insulin sensitivity and improve glucose tolerance. I’ll be writing an article on this soon.

Bryan Opfer December 19, 2010 at 5:18 pm

Chris, I just got some blood results back:

FBG: 78
A1C: 5.4
HDL 63
Trig: 65

The A1C # seems high. My diet has been Paleo+raw dairy since April 2010. However, I was borderline anemic on a few tests during late summer. Think there’s anything to worry about with that A1C number?

Chris Kresser December 19, 2010 at 5:40 pm

Bryan: test your post-meal blood sugars. A1c isn’t particularly reliable in that it can be influenced by a number of different factors. If your post-meal #s are normal, I wouldn’t worry about the A1c – especially in light of your FBG. You could also run fructosamine, which is another measure of average blood sugar that isnt affected by hemoglobin variation.

Bryan Opfer December 20, 2010 at 12:15 am

Thanks, Chris. I am going to pick up a glucose monitor this week. BTW, fructosamine was 1.9 in that same blood work.

Chris Kresser December 20, 2010 at 9:03 am

Assuming fructosamine was measured in umol/dL, 1.9 is excellent and suggests you don’t have elevated blood sugars. But the glucometer is most accurate, so still a good idea to do that.

Bryan Opfer December 20, 2010 at 9:09 am

It was measured in mmol/L. The report says that 1.2-2.1 is “normal”

Chris Kresser December 20, 2010 at 9:19 am

Okay. Since it’s getting towards the top of the range, probably good to test the post-meals.

simona December 23, 2010 at 2:03 pm

Hi Chris,
is very low fasting insulin (below the range) something worth considering or it is just good?
2.073 mcIU/ml (you mentioned <5 mcIU/ml) or 14.4 pmol/l less than 16.5 lower end of the lab range
at the same time glucose was 5.2 mmol/l or 93.69 mg/dl a bit high
I was eating low carb which could explain the higher glucose but previously in the last 2 years since I'm low carbing my FBG has been low 4.5, 3.9, 4.1. or under 81.

Chris Kresser December 23, 2010 at 2:20 pm

Fasting insulin is an inaccurate marker, especially in the mid-to-later stages of insulin resistance. I think post-meal blood sugars are more useful in measuring insulin sensitivity and glucose tolerance.

Bryan Opfer December 23, 2010 at 5:27 pm

Hey Chris, I did my glucometer testing. Here are my results for premeal, 1,2 and 3 hours after:

Day 1: 87, 96, 100, 87
Day 2: 89, 101, 114, 94
Day 3: 92, 151, 141, 80

I had white rice on day 3, which apparently I should not eat. Anything else I should gather from this?

Chris Kresser December 23, 2010 at 5:49 pm

Looks pretty normal except for the white rice. Definitely want to avoid that.

Chris Kresser December 23, 2010 at 5:53 pm

Oops. My response got submitted before I was finished.

One potential question mark is that your 2-hour reading was higher than your 1-hour on two days. That can indicate a compromised or delayed insulin response, or in some cases, slow digestion. Still, the important thing is that you’re below 140 at one-hour and below 120 at two-hours which you are in all cases except the white rice day.

Bryan Opfer December 23, 2010 at 6:14 pm

I definitely have digestive issues (IBS-C) that I have been working on for a while. It was IBS-D before I eliminated gluten. Also had a positive ANA test, so possible autoimmune issues, although lupas was ruled out. My new years resolution might be to book an appointment with you.

reem January 1, 2011 at 10:38 am

Hey chris, me again ;)
I followed your advice and continued to test. I’ve been eating 30-50g carbs for several weeks now (in the form of white rice or winter squash).
Yesterday, i tested my FBG and it was 77
Today I ate 40g carb in the form of white rice, and 1 hour later it was 171 mg/dl!!! i just tested it now (1.5 hrs later) and it is 158.
I don’t understand, i wouldve thought my body would be used to the carbs by now?? However it may be worth mentioning, that the past few days i have been recovering from jetlag and my sleeping cycle has been really messed up (going to sleep really late, sleeping 12 hours or more..) so maybe this has disrupted by BS balance?
It still doesn’t make sense though that my FBG is normal, yet my response to carbs is insanely abnormal.
BTW, I’m 20 yrs old, and have never been overweight. I’ve been eating LC for a few years now (and before that a high carb moderate fat diet, and before that a junk food, high carb high sugar high gluten and everything bad diet)

I appreciate your thoughts!!

lynn January 1, 2011 at 10:55 am


How long have you been eating higher carb? Glucose tolerance TEMPORARILY decreases on LC and will be higher at first. I once got a BS of 170 when I first moved to a higher carb WOL. Now I get a MAX BS of 120 for the same amount of carbs.

So, give it time. Also, be aware that protein increases BS. You might be very surprised to find that a potato with some butter will cause less of a spike than a steak with potato. Strange, but true.

Chris Kresser January 1, 2011 at 11:58 am

It’s actually not strange at all to see normal FBG and impaired post-meal blood sugars. There are studies showing that people with normal FBG and impaired OGTT are at higher risk for developing diabetes later on. I don’t say this to scare you, but to clarify why post-meal #s are a better indicator of glucose tolerance and insulin sensitivity than FBG.

It may be that your numbers come down further after more time. However, it’s possible that you have LADA or some other process affecting insulin output or sensitivity. The low-tech response is to simply avoid whatever raises your blood sugar above 140 mg/dL if you continue to experience this.

David January 12, 2011 at 9:02 pm

Hi Chris,

Just spent five days collecting BG levels. Found this article after as many days of searching–most searches return information for diabetic rather than non-diabetic scenarios so it took awhile.

I’ve gone on a keto diet on-and-off over the last 10 years and always feel dramatically better on one, but eventually grow weary and give it up. Idea is that the glucometer will help motivate me to stay mostly low-glycemic even when keto grows old.

As expected, my levels are below ADA pre-diabetic, but are not idea by the standards of the studies cited above. Will be interesting to see if I can knock the 10-20 mg/dl off the baseline over time.

The thing I find interesting is that my BG level goes up quite a bit after each of my three weekly weight lifting sessions. I work out pretty hard and consistently, always going as close to maximum intensity as reasonably possible. Today, three days into keto, my BG was 95 before a lower-body session and a tad lower at 93 at the end of the session. Twenty minutes later it went to 120 mg/dl and gradually drifted back down to 105 over two hours. Haven’t eaten since hours before the session. Before switching to keto BG peaked at 130 after lifting. On cardio days (500 kcal in 35 minutes rowing) BG followed a similar pattern on high-carb and was close to flat on keto, rising 10 mg/dl at the end of the workout and staying there.

I’ve read that an increase in BG post-workout is to be expected since the liver brings glucose out of storage for muscles to use, but can’t find much information on what levels would be reasonable to expect for an normal to mildly glucose intolerant person.

Do you have any information regarding this? Any interesting studies?



MommyD February 24, 2011 at 10:04 pm

How would all this apply to children? would the numbers be the same as adults? If not, could you share what optimal levels would be for kids? I would love to show my kids what happens to them after they junk out on high sugar foods!

deb b March 4, 2011 at 11:16 pm

My post exercise BG# is higher after weight work out (but is lowered with 10 min of “easy” cardio). Would this be “expected” (I’m paleo). Also, BS is often higher after overnight fasting. Does this indicate that glucagon or gluconeogenesis has kicked in as BS drops during the night?

At some point, can you define “low carb” ….I get my carbs almost exclusively from low glycemic veg – but these can add up. When people are quoting under 50 grams of carbs per day, does this usually mean TOTAL carbs, or are then netting out fiber? I can easily eat 3 cups raw brussels sprouts (yields about 2 cups cooked) either way total carbs are about 24 grams. Same for cabbage, etc.

reem March 6, 2011 at 8:13 am

I#ve been continuing eating the same way for the past few months, but still no improvement. Occassionally my blood sugar readings are normal (especially if i eat alot of fat with carbs, or i eat them after a workout or with whey protein).
However today i ate about 80g carbs (white rice) with about 2 tsp fat (first thing i’ve eaten today)

12pm – ate half the rice
12:30 – ate the rest of it
1pm – 128 mg/dl
1:30pm – 174.6
2pm – 156
2.30pm –

Clearly i have problems..I called my doctor the other day requesting hbA1c, etc, but she refused because i am “20 years old and not a diabetic”

I’m really not sure what to do now. I#m cutting out the white rice,and will see how other starches affect my blood sugar, but is there any way to reverse this? Any supplements/nutrients to take, lifestyle changes, etc? How can i find out what is going on with my body?
Would appreciate any advice as i’m really at a loss here…

deb b March 6, 2011 at 11:02 am

Could I suggest trying to immediately replicate? i.e. if you get one that high (174.6) immediately do another stick. This happened to me today. I have been testing a lot the last 24 hours and knew from the quantity of CHO I had eaten my BS could not have increased as high/fast as it did. I retested using “better technique” (I got a bigger initial drop of blood and it filled the strip more rapidly) and this time it was what I would have anticipated. I sometimes use two glucometers side by side (there is far more variability than it seems there should be). Also, next time you are having a lab fasting BS, take your glucometer and do finger stick just before the draw – then you will have an idea of the accuracy of your meter. Bayer Contour is working best right now – but I am using up my Accu-check strips, just as a relative indicator (i.e. does exercise make BS go up or down), as it routinely runs 10-20 higher than the Bayer.

Question for Chris – from the “data” (google David Mendosa ‘Free Foods’ blog article where Dr. Bernstein weighs in) we would expect that 10 gm CHO will increase BS 50 in Type 1 and non-obese type 2. Do you have an “overlay” for low-carb/Paleo type eaters? I am wondering if this might also happen?

Still trying to understand why intense exercise (kettlebell type work out for an hour) in a fasted state increases blood sugar, while 10-15 min easy cardio (treadmill walking after mea) decreases. Does this make physiological sense in terms of glycogen and glucagon kicking in:fasted state and muscle uptake of glucose: fed state?

Other ideas: Listened to a lecture on continuous blood glucose monitoring results. It showed (in agreement with what Calorie Restriction society says) that your am (first) blood glucose response is the strongest (insulin production is shut down from the overnight fast, and needs to be gently teased awake – not shocked with a quick glucose spike). This is great reinforcement for NOT starting the day off with CHO (especially something as glycemic as white rice).

Chris Kresser March 6, 2011 at 8:19 am

Reem: seems your glucose tolerance is impaired for some reason. There’s no way of knowing why without investigating further. The typical culprits when blood sugar doesn’t improve with dietary changes are cortisol dysregulation or (less likely) late onset autoimmune diabetes (LADA, or Type 1.5). A1c isn’t particularly helpful in this situation – post-meal #s are much more accurate.

reem March 6, 2011 at 12:20 pm

thanks for the quick response. Is there a way i can get tested for cortisol dysregulation or LAMDA?

Eddie March 9, 2011 at 9:44 am

I’m eating Paleo / low carb and have just started tracking my blood glucose. A typical day sees me at a average of 5.5mmo/L of 99mg/dl, no matter if it’s FBG or post prandial. Also, my 2hr post prandial is the highest. Can you touch on delayed insulin response on a future podcast? Should I be aiming to get BG any lower? A1c results are due in the next week, so that’ll reveal more.

Date Time mmol/L Notes
09-Mar 06:13 5.1 FBG
09-Mar 08:05 5.2 Post workout, fasted, 10g BCAA
09-Mar 08:50 5.5 Post workout, 10g BCAA
09-Mar 12:21 5.4 Pre-lunch
09-Mar 13:31 5.4 1hr post prandial
09-Mar 14:31 5.7 2hr post prandial
09-Mar 15:28 5.5 3hr post prandial

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