Diabetes Testing

Is a Lower A1C Level Better or Worse?

It seems logical that the lower our blood glucose levels are the better we will be. Most of us have always assumed that lower blood glucose levels would protect us better from the complications of diabetes. In fact, during the past two decades several studies showed a linear relationship between blood glucose, as measured by A1C levels, and worsened health.

glucose meter

But now, several recent A1C studies have shown a J-shaped relationships, in which at the lower end some bad things happen, at the center things are better, and at the top end things are terrible. While linear relationships are the rule in observational studies, U-shaped and J-shaped curves aren’t uncommon, and some authors lump both of these shapes as U-shaped.

All of the studies relating A1C levels and ill health — the earlier ones and the recent ones alike — are observational.  They study correlations, which aren’t proof, because other confounding factors that the researchers didn’t take into account could have been the problem.

5.4-5.6 Seems Safest

The first of these newer studies showing that a very low A1C level is unhealthier than a higher one came out in the February 2015 issue of Diabetes Care. This analysis of the German National Health Interview and Examination Survey 1998 that studied about 6,300 people for about 12 years indicated that people with an A1C level of 5.4 to 5.6 had the lowest risk of excess mortality.

Because this result puzzled me so much, I asked Dr. Richard K. Bernstein for his reaction.

“These A1c measurements were made years ago in Germany,” he replied, “before international agreement on how it would be measured. The modern elution method would likely give considerably different results. It is even possible that several different methods were being used at different sites during the study.”

A1C and Dementia

Even more recently, however, I came across a similar finding for a specific complication of diabetes — dementia. While the study itself, which I reported here last month, doesn’t report the finding, the author subsequently stated that “very low HbA1c levels were associated with increased risk of developing dementia.”

What’s the cause and what’s the result is the question, Dr. Naveed Sattar commented. “In people who have very low blood glucose levels, below guideline levels, I suspect that there are other reasons that they are sick and their A1C is low because of this and that then leads to dementia,” this professor of metabolic medicine at the University of Glasgow, says.

Recommended Targets

A1C target levels are based, of course, on minimizing the complications of diabetes and take into consideration the levels that people without diabetes have. But the targets vary widely.

The latest recommendations of the American Diabetes Association in its current “Glycemic Targets” for most people is a level below 7.0 percent. The ADA adds that we may have “more stringent A1C goals such as below 6.5 percent” if we don’t take diabetes drugs that can cause hypos. The ADA doesn’t say here what they consider a normal A1C level to be.

The ADA’s recommended A1C level is one extreme. Dr. Bernstein stands at the other extreme. “A truly normal HgbA1C ranges from 4.2 percent to 4.6 percent,” he wrote in Dr. Bernstein’s Diabetes Solution (fourth edition, page 57). On several later pages of this book, Dr. Bernstein states that this should be our blood glucose goal.

Normal Levels

I haven’t been able to find any studies that support either extreme. One small study that I discussed in “The Normal A1C Level” here several years ago indicated that a normal level is probably between 4.7 and 5.7.

This study is in fact consistent with an ADA study in its journal Diabetes Care by a group of a dozen of our most well known diabetes researchers who set out to define what our A1C levels would be if we were for all intents and purposes cured of diabetes. This “consensus group” of experts defined cure as complete remission for a long enough time that the risk of recurrence is very low. Specifically, they determined that this A1C level is one in the normal range for at least a year without taking any diabetes drugs of ongoing procedures. That level, they write, is 5.6.

New Goal Levels

On a very low-carb diet we can easily bring our A1C level down to 5.6. Personally, my level has stayed close to 5.5 in dozens of tests for the last eight years on such a diet and without using any diabetes drugs. But until now I longed to bring my level below 5.0, much closer to Dr. Bernstein’s recommendation.

I wonder now, however, whether a level of about 5.5 might be the safest. While nobody knows for sure what the best A1C level is, it seems clear that it for our safety we must keep it below 6.0.

This article is based on an earlier version of my article published by HealthCentral.

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  • Dev at

    David Mendosa-

    Thanks for your contribution for this deadly disease.I would love to have your comments & article on Intermittent Fasting.


    • David Mendosa at

      Thank you, Dev. Actually, I have already written several articles here about intermittent fasting. Please check them out!

  • LaBerta Finck at

    Dr. Mendosa, thank you for responding. I realize the A1C is an average for three months and now I won’t worry as much. My Triglycerides came down a small amount but I am happy with whatever I can get. After all I am 77 and making changes that I will follow for whatever remaining years I have left, and over the past 15 years I have gradually moved to healthier choices anyway.

    • David Mendosa at

      Very good, LaBerta. The worry never helps! But the more that you follow a very low-carb diet the greater the reduction in your triglycerides will be. I was personally amazed at how fast and far mine went down when I started low-carbing.

  • Ellen at

    I realize that most of your readers are probably Type 2s, and I am a very late-onset Type 1 (in my 50s, at first diagnosed as 2, but later changed because producing zero insulin). But it is very discouraging to read that we should keep our A1c below 6 (or even below 5!) “for our safety.” I am on a pump and work extremely hard to eat low-carb and exercise (though probably not enough), and I work regularly with a diabetes educator, but the best I can do after several years is mid-7s. My endocrinologist thinks that’s actually pretty good, but reading articles like yours just makes me feel like the mountain is impossible for me to climb. I’m otherwise healthy, but I am depressed about this. Am just venting, because the data is what it is, I guess. Thanks.

    • David Mendosa at

      I sure didn’t want to depress you, Ellen. Take it one day at a time.

  • LaBerta Finck at

    Having been diagnosed as pre-diabetic in June, I went low carb and stopped eating candy and desserts. My glucose is down from 103 to 85 but I am concerned about my A1C which has only gone from 6.0 to 5.8. I am hoping it will bet a bit lower but am wondering if I should still be as concerned about it. Someone had said that they kept theirs at 4.5. I don’t think after reading this blog that I want it to get that low.

    • David Mendosa at

      You are doing well, LaBerta. The A1C level changes slowly, so be patient!

  • Marilyn at

    An interesting concept Michael K. Perhaps someone will come up with a reference.

  • Michael K at

    I have mentioned this to you in the past but I will repeat it here. I wish I could remember where I read this but A1C levels in Diabetics are not apples for apples with non diabetics because diabetics red blood cells do not live for the same amount of time as non diabetics. As I remember a 5.6 in a diabetic could actually reflect a higher blood sugar level than a non diabetic.

  • Marilyn at

    David, I think what I’m really asking is that if your HbA1c is consistently 5.4 and not reduced further by a continued good adherence to a very low carb diet, then perhaps Dr Bernstein’s view that an ideal HbA1c should range between 4.2-4.6 is simply not attainable for some and that for those individuals a range between 4.7-5.7 is completely healthy and not diabetic? Isn’t that what your post is essentially saying?

    • David Mendosa at

      What a great question, Marilyn. I think that the reason why my A1C level stays around 5.4 is that I am not sufficiently motivated to bring it lower because I actually think that a level of 5.4 is good enough. I hope that I’m right, but only time will tell.

  • Marilyn at

    I’ve been very low carbing for well over 2 years now and my HbA1c reduced from my first reading (pre low carb) to 5.4 and stayed there. I’m not a diabetic but as I consistently have blood sugars around the 6.0 mark, my GP considers me to be at prediabetic levels. I have often wondered how much ‘room’ there is for ‘normal’ readings to have a naturally broader range.

    • David Mendosa at

      A level of 6.0 is right on the cusp, Marilyn. Could you explain your question a bit, please?