High A1C doesn't match my meter readings

I just got my most recent A1C results, and I was very confused to see that it was 6.1. My last one was 5.6 and even that seemed way too high judging by my meter readings. I test a lot, sometimes 12 times a day, and I also eat a lot of the same things so I know how my BG reacts to my diet. My fasting BG has been a little higher recently, but only about 90, and I rarely go over 120 at an hour. By 2 hours I am back under 100. According to my meter, my average is about 100 at the moment. I read somewhere that the A1C corresponds to your average after meal number because that is when glycosylation takes place. This would make some sense because my highest number after eating is around 125. I know Jenny posted about this on her blog. Anyone else have a similar experience? I am also wondering about the fructose test. Has anybody had this? I do eat a mostly vegetarian diet but not a whole lot of fruit.

“Two individuals with the same average blood sugar can have A1C values that differ by as much as 1 percentage point)”

From: http://en.wikipedia.org/wiki/Glycosylated_hemoglobin

Typical A1c test methods are off by +/- 0.3 frequently and by +/- 0.5 or more at least 3% of the time according to research published by Larry Fox and also the team at DirecNet so it’s hard to say. There is also the possibility that your blood chemistry contains one or more aspects that interfere with the A1c test; things called hemoglobinopathies which are not typically screened for. The NIH just published an advisory on this, too.

Read more here…

I’ve never experienced anything like this, but have you tried all the checks on your own meter? Also do you keep a running average on your meter? Look in Dr Bernstein’s book or on the web to see if your average is a long way off the expected A1c. I’m in England and so only really know the numbers in mmol/l where the lower numbers basically almost line up, so an average of 5mmol/l corresponds to an A1c of 5%. also is your meter calibrated correctly? Sounds like a silly question, but I scared myself the other evening with a reading of 8.5mmol/l (,about150mg/dl) when I knew it shouldn’t be that high. I had stupidly forgotten to recalibrate after I opened a new pack of strips. Even after having this meter a couple of years, I forgot.
Having said all that, 6.1% and 5.6% are way better than many people manage to achieve. I’m just waiting on my latest results and will be happy with 5.5%.
Lastly, in my jumbled thinking,you say your numbers have been a little higher lately. How long since your previous test? A red cell has a life of about 120 days and so A1c is more accurate over that length of time.

I do callibrate my strips and have tested my meter. Plus my meter always corresponds to how I feel and to the number of carbs I eat. For example, when I accidently drank a real soda, I was at 220, when I eat a small apple, I go up to 130. I’m guessing I am just an oddball whose A1C does not correspond because my first A1C of 7.2 was way, way higher than my BG suggested. I have a very robust second phase insulin release and never go much over 180 at 1/2 an hour, even with a high carb load. Then my BG drops rapidly till I get a fairly low rebound and some hypo symptoms. So on diagnosis, I was bouncing between 180 and 60 with a fasting rate of 80. Shouldn’t have translated to a 7.2, which is an AVERAGE of about 170.

I have no more ideas, but I noticed one thing I find interesting in your reply. you say your meter corresponds to how you feel. That’s fascinating. I don’t feel any different unless I go very low, which rarely happens as my medication shouldn’t allow it. I’m using Metformin and Starlix. I never go very high, so I don’t know how that would feel or even if I’d know.

I just spoke with the school nurse and she suggested it might be tie for a small amount of basal insulin. And that I should have my fructose level checked. I’ll try those things. As to how I feel, I’m pretty sensitive to anything over 150 or under 70 and those are rare numbers these days for me. I can’t imagine that my true BG numbers are 40 points higher than I am getting since I would notice if I was going high enough to average 125.

umm an off idea? Might you need to put a new set of batteries in your meter? Sometimes my numbers look weird and I change for a new set and things match up better with the Dr office.

I’ve always had A1cs higher than my BGs would seem to indicate. I even tried a CGM to see if I was going high at night or at unexpected times of the day, when I wouldn’t think to test. I wasn’t.

I’ve tried talking with the techs at LifeScan to see if possibly something in my body chemistry or vitamins could be causing falsely low BGs on my meter, but they couldn’t come up with anything (not that they tried very hard; just spouted the usual stuff).

Remember that the A1c assumes your red blood cells live 120 days. If for some reason they live longer than that (RBCs of people without spleens do live longer), your A1c will be higher than expected. If they live a shorter time than that, for instance if you’ve given blood or if you’re anemic, your A1c will be lower than expected.

Researchers used to think that some people are just “good glycators” and glycate hemoglobin more robustly than others. That’s possible. But I’ve seen recent papers suggesting it’s more likely red blood cells that live longer than usual.

I think the important thing to focus on is whether your A1c, done at the same lab, is going up or down consistently, or staying the same.

Many medical people assume that you’re testing wrong or sneaking sugary treats and not mentioning them. Ignore them. There’s probably something in your physiology that is causing different A1cs than expected.

I’m picking up on your comment about people’s assumptions.
I’m maddened by the assumption that if something is anomalous, you are telling lies. I don’t get this with my present health-care team, they’re great! ( even if they don’t approve of low-carb diets) However I do remember getting it when my daughter, now a married woman, was small. The receptionist, who answers the health centre phone got the sharp end of my tongue at least once.

It’s not just health care people. You can spend 5 hours trying to solve a complex problem with your computer system, finally give up and call tech support, sit on the phone for 30 minutes, and then have the person ask, “Is it plugged in?”

The problem is that many people do forget to plug the computer in and do use the wrong strips or don’t wash their hands before testing and do say they’ve been following their diets when they’re not.

Those of us who don’t fit the standard profile just have to learn to let these things wash over us.


Read this article. It indicates that your A1C will more reflect you last 30 days that the 90/120 total average.


More, yes. But there’s still some effect of the older levels.

I think your idea about the age of the red blood cells must be the rreason. The fact is that I have never gone over 140 ever, so it is not an issue of the last 30 days. The research shows that the better your BG control, the longer your cells live, so that paradoxically you have a higher A1C. I have been testing more frequently and know for a fact that 45 minutes after eating my BG is about 135, one hour it’s at 120 and at 2 hours it’s at 95-105. Fasting and over night is very constant at 90. That is not typically an A1C of 6.1. My A1C seems to correspond with the one hour number rather than the true average. it makes some sense that if my cells are living longer than 120 days, they have more chances to pick up glucose and they pick it up at around 120. However, your comment about looking at my own trends is a good one, and my A1C IS higher than it was 6 months ago, in spite of a better diet, so I am guessing that’s to do with my higher fasting rate. I will give it a couple of weeks to see if it settles back to around 80 and if not, I will talk to my endo about a low level of basal insulin. Thanks for all your help.

Here’s a reference that includes graphs of mean BG and A1c for different people. The mean relationship is linear, but there’s a tremendous amount of scatter. From graph A in Figure 2, it looks as if a person with an average BG of 5 mmol/L (90 mg/dL) could have an A1c from 4 to 13! And the average would be about 6.5. This is very different from the formulas they use to calculate average BG from A1c.

Your point about the worse control destroying RBCs is also a good one that those with higher A1cs should remember.

Wow, Gretchen,
That’s a complicated article. It worries me a little though that it seems to suggest that a higher A1C does correlate with greater risk for complications regardless of the cause: higher MBG or higher glycation. I am thinking that it would make sense to try basal insulin as a way of getting my A1C to come down lower. It is frustrating though to think that I can achieve near normal BG and yet still have a pretty high A1C with its concommitant risk factors. The RBC longevity theory doesn’t fully explain it since non-diabetics have longer lasting RBCs and they have A1Cs in the 4.6-4.8 range.


SOME non-diabetics have A1cs in the 4.6-4.8% range. Many, however, are in the mid-5% range, like my partner who has never tested over 115 and still gets 5.4% A1cs.

If you do try a basal, stay away from NPH. Two weeks on it and I seem to have developed antibodies to R which made it stop working properly. Coincidence? I don’t think so, even if I can’t come up with a mechanism to explain it. I had been doing so well on R for so long before that. My guess is it has something to do with a reaction to the protamine.

I think a higher A1c definitely correlates to higher risk of complications. But again, this is an average, like the relation between BG and A1c. Some people have good A1c’s and don’t have complications. Others have lousy A1c’s and get complications. If I come across a graph showing individual results of A1c vs complications, like the graph of BGs and A1c, I’ll let you know.

What are the other options for basal insulin? I really don’t know anything about it.

I have always had a much higher a1c reading compared to my meter. My meter may read 140 and my a1c would equate to 180 or higher. Now that I have a cgms my a1c has dropped to 6.7 and 6.8 for the last 6 months. There were many times I didn’t know I was 180. My cgms now tells me.