A1c variation

I posted this in another forum, and then thought everyone should have a chance to see it. It's something I learned at misc.health.diabetes many years ago, but still seems not to be common knowledge.

Something that MANY people and docs don't know: people glycate differently. There can be as much as a 1% difference either way. So my 6% (I'm a low glycator) is equivalent to someone else's 7% ( a "normal" glycator) and even another person's 8% (a high glycator). I never had an A1c above the 6's, except when I was out of control and symptomatic in the beginning, when I had a 7.1%, and then when I got sick last September, and had a 10.7%. For me, that was LIFE-THREATENING; other people walk around with considerably higher A1c's and don't go into comas.

So the lesson is that docs SHOULDN'T rely on A1c alone, because if you are a low glycator, you might have an "excellent" A1c, and still be peaking well above 200 after meals, and never achieving a fasting BG below 150. (Me, when I was at my most symptomatic, with an A1c in the low-to-mid 6's). Conversely, those who bemoan the fact that they can never get their A1cs below 8% may be high glycators, and although they should still make the effort, maybe a 6% is simply unreasonable for them.

I am perturbed about the movement to make an A1c > 6.5% diagnostic for diabetes, because it will overlook some Type 2's in the early stages, when their BGs may not be catastrophically high, but still high enough to cause damage. There are already too many Type 2's who present with complications already present -- no need to make things worse!

Ideally, the doc should look at the whole patient -- A1c, yes, but also BG logs, diet habits, exercise habits, and life stressors before making a treatment decision. Possibly an OGTT and a professional CGM trial for 5 days (3 days is not long enough).

It seems to me that it would be better to catch some pre-diabetics, when they really do have a chance to improve their BGs with sensible eating and exercise than to let others go until they have started to go blind, have nephropathy (a lady I know is obese, has nephropathy and leg ulcers, and the doc insists she is not diabetic), etc.

Rant over, LOL!

So how can you tell if you are a low-glycator or a high-glycator? I’ve heard of this and have sometimes wondered if I am a high-glycator because even with maximal effort I can’t get an A1c below the high 6s. Now this may also be because I am missing highs and such, but when I went on a seven-day CGM trial the CGM data corresponded almost exactly to my meter data. In fact, I missed more lows than highs. I know other Type 1s who have similar numbers to mine yet have their A1c stay in the low 6s. I also think too much emphasis is placed on A1c, and recent research is showing that glucose variability (the swings from high to low each day) may be even more damaging than glucose average.

Well, I tested my BGs a lot, and then looked at the charts they have comparing A1c to average BG. When the chart said that an A1c of 7 was equivalent to a BG average of 154, and my A1c was 7.1, and I was NEVER under 150, and usually closer to 250 (or higher), I knew that the chart didn't apply to ME. I also knew that before I was diagnosed, I had lab fasting BGs of 138, and 3 months later 131, yet my A1c at a diabetes fair 2 months after that was 4.8. Here I was, running close-to-diagnosable BGs (the cutoff at the time was 140), and yet I had a lower A1c than many proven non-diabetics run (they can go up to 5.7 or even 6.4 and still not be diagnosable as diabetic). The third proof was that I went into a life-threatening coma with an A1c of 10.7, when I know that other people have 12, 13, or 14, and are still walking and talking.

So what I am saying is that the numbers do NOT correlate all that well with A1c, and your meter is your best friend.

Unfortunately, it may be that high glycators also have more glycation in other tissues, and be more at risk of complications, but I have never seen anything authoritative about that, pro or con. I wish there was more research on A1c variation, instead of this blind acceptance of the idea that everyone is the same.


Above are some scatter plots showing the relationships between A1C and average bg. Data is from DCCT participants.

You see a huge amount of scatter. i.e. A1C is not as precisely related to average bg, as those tables that others post on the web saying that an A1C of 7.8 is an average bg of 174 and an A1C of 7.9 is an average bg of 177. This is the value in a scatter plot. A scatter doesn't tell you "the right answer" but shows that there are ranges in any physical measurement due to a wide variety of factors. This really bothers those who believe that there is a "right answer" to a measurement, as if it were just reading a dollar amount to 5 decimal places out of a bank computer.

This doesn't necessarily mean that anything is "wrong" with the A1C, just that like any physical measurement, interpreting the data requires some broader context.

I strongly believe that when someone includes A1C as part of the diagnostic criteria, they mean to do so in a broad context. That doesn't mean that it will be interpreted by all readers in that same broad context.

Incidentally, I'm one of the "older generation" that was diagnosed as diabetic with no blood test at all. (In fact for the vast majority of the past couple millenia blood glucose was far harder to measure than it is today with our handy dandy pocket meters, and in fact it is only in the past decade or two that bg measurements have become primary rather than secondary diagnostic criteria for diabetes). Blood tests have huge value but we should all remind ourselves (and our docs) that we are much more than just a bunch of numbers on a lab report.

I know when I was first diagnosed, my fasting Glucose was 118. Three weeks later I was sick as a dog and had a BG of 719. So you know what happened? Was the test bad? or did things just give out and wham the big day had come. My glucose tolerance test three months before was normal so agian what happened?

I know now ever one wants to know why in the world I was being tested so much? Well my mom had the disease and I was 16 and about to go on a two month backpacking trip. Mom was paranoid that something might happen, so she talked the doc into doing the annual tests early and in rapid succession. The Doc and especially I, thought she was nuts. So we as a family took off for a 10 stay in Disney Land and whamo I was so sick I could not even hardly stand up. Well so two things happened. First I spent my 17th birthday in the hospital (actually I got out that day) and yeah Disney world is not always the happiest place on earth. Oh and one more thing I still went backpacking. No question today we would never let someone do that. But hey, mom was happy she proved her point.

Actually expect for ruining a long waited trip to Disney World things turned out ok.

rick phillips

Regardless of your number, the question isn’t “what is your number?” but “what are you going to do about it?”. I watch my average but I realize that it’s not accurate because I have to ‘ping’ my pump w/ fake readings to check IOB several times/ day too All of these tests have margins of error as well so I think that the thing to do is to be proactive and develop strategies to improve or maintain your level regardless of what it is? If nothing else, diabetes in this day and age is like a video game, where you have numbers blasting you all the time and you might as well blast back? I guess if you aren’t dx’ed but your numbers are off, you might be tempted to try to be proactive and fix your almost off number by running up and down the stairs or something like that but you are still dealing with a lot of numbers. Even if you aren’t diabetic, you could perhaps test your bg to find foods that are better, avoid cholesterol and do other proactive number things that people w/ diabetes do 12-15 times/ day (at least…) but I’m not sure what the goal of adding more categories into the mix as far as “standards” would be anyway?

Completely off-topic, but did some DCCT participants really have an average BG of over 40 mmol/L? That is really incredibly high!

It's trivially easy for me (and I like to think my control is pretty good at least most of the time) to hit 40 mmol/L... just miss a dose of insulin. Most home bg meters don't register well with numbers above 800 mg/dl or 44 mmol/L... I know mine just says "HI". I say "Hello" back when that happens :-).

You might get the impression from reading tudiabetes or other web-boards that your typical diabetic has an A1C or bg just a little above normal. Even today there's some stigma that prevents those with any but the most mild or well-controlled diabetes from sharing their experiences and numbers, much of the time. e.g. the cult of "any number above 140 means doom!".

I agree with you that it’s easy to hit HI (though on my meter that’s anything above 33.3 mmol/L, I haven’t heard of meters that go higher) just by missing a bolus or two or having a pump site go bad or something.

Your A1c is better than mine has ever been and I don’t think I have ever gone a day in my diabetic life where I haven’t been above 7.8 (140) a good portion of the time (this is why I tend to avoid those “above 140 is doom!” threads). I am sure in my Regular and NPH days I hit HI after a significant portion of my meals (but of course we never tested after eating back then, so I’ll never know)! So I am by no means trivializing how hard it is to have good control.

It’s just the idea of someone being that high as an average, all the time, that surprises me, rather than the number itself. I have known of out-of-control Type 1s who hang out in the 20s and 30s (350-600s) constantly, but 40-50 mmol/L is significantly higher than that and I would think these people would be going into DKA constantly.

Even though this thread started with the difficulties of precisely measuring A1C's I think there are similar difficulties with measuring average bg's. I think most of the scatter in the plot is high glycators vs low glycators vs labs with less than perfectly standard A1C calibrations (incidentally... reference ranges between labs for A1C's still vary by substantial amounts!!!) but realistically there is also error in the measurement of "average bg".

In the DCCT era most of those "average bg as measured at home" numbers were probably read from Chemstrips, or Ames Glucostix (some here think the Chemstrips were primitive... bet they never had to use Glucostix!!!! And those were 100 times better than urine testing!), and neither were awfully accurate at the high or low end (just like all of today's meters don't give a number at all but say "HI" above some threshold). Above a certain point the number really is just too god-awful high to worry about whether the exact number is 40 or 35 or 45 mmol/L... they're all too high!

And yes, a certain fraction of patients are teetering around in DKA much of the time. It's a sucky place to be. Again, so many of the frequent posters here have such excellent control you might think that the only obstacle a typical diabetic faces is keeping post-meal numbers under 7.8 (140 mg/dl) and A1C below 6.0. But realistically a huge chunk of the diabetic population (T1 and T2) has far far worse control, with bg's frequently above 25 mmol/L (450 mg/dl) and A1C's in the 14-17% range.

It's ironic that those with such good control are such frequent posters, when they probably don't appreciate at all the plight of someone who hasn't seen a number below 450 mg/dl in a long time, and those who struggle to get their A1C's below the 14-17% range probably don't appreciate at all the issues of those keeping A1C's in the low 5's. I like to think that I can see both sides of the situation, because although I often am able to get good control I know that sometimes the difficulties seem insurmountable and my numbers may go into the stratosphere at the slightest provocation, and that I have also ended up with 911 calls and ambulance rides for hypos too, but maybe I don't really understand the two extremes as well as I think I do! Certainly the lectures I get from those in excellent control sometimes seem like they are intended for someone who is NOT me :-)

I'm *not* extreme! I think that whether you aim for 5-6-7-8-whatever, diabetes is a lot of work. You can work on your BG or you can blow it off but it will still be a lot of work and a mental weight. You can deny it and rot but it will *still* be a lot of work.

I don't think that there's a lot of conclusive medical evidence about what happens when you run < 7 (*cough cough* Tim...:-)) because the medical industry is too intimidated by lawsuits or their own heirarchical standards to explore what it seems like quite a few of us are doing, fairly safely most of the time?

That is a good point about the use of colour-coded strips. I believe the DCCT ran from 1983-1993, though, so for at least the latter half of that I would think home meters would be used? At least, when I was diagnosed in 1991 they seemed to be the norm, but maybe I was just lucky and had a really up-to-date medical team. I can imagine the colour-coded strips would be far less accurate than even the most primitive meter, though.

I cannot relate at all to people who complain about an A1c of, say, 5.8%, or who complain about their A1c going “up” to something like 6.3%. Or sometimes I see posts from being about their blood sugar “going crazy” when their range throughout the day has been from 4.5 to 9.5 mmol/L … I personally would kill to have such good A1c numbers or such a flat range. It’s probably similar for people who have and A1c in the teens looking at the numbers of even those of us with a “high” A1c compared to most on these sites.

Tim wrote: "those who struggle to get their A1C's below the 14-17% range"

As a low glycator, I would be dead long before I got into a range that high!!!! (I already tried it!)

But that's precisely what I was trying to say in my original post. It's nonsensical to compare average BGs OR A1c's. For me, riding in the 6's is just like Jennifer's riding in the 8's. I almost NEVER stay under 140 after a meal, and I usually peak between 180 and 240. That's why I posted my VERY unusual semi-flatline to Flatliners! My fastings have been running in the 130's lately, but I still bet you I'll have an A1c in the low to mid 6's.

I certainly empathize with those who have wild swings. Since I have the easiest and best type of diabetes, I don't usually have those problems (although I HAVE been in both places -- low 32; high HI, couldn't get below 400 - HI for about a month, resulting in a diabetic coma in September), but it only takes a little bit of human empathy to know and appreciate how much someone is struggling.

If some of those who are struggling would post more often, they might see that others have more empathy, and offer more support than they think. When people offer suggestions, it's out of good will -- I don't think they are lecturing you. Most of the time, they are offering personal experience, but I think we all know everyone is different. Type 1 IS the pits, especially when you've had it for a long time, and if you're doing your best, at least most of the time, I don't think anyone can fault you. And getting complications is worse than the pits, but what choice is there but to carry on?

Or maybe I'm weird, because I DO care about the people who are struggling?

I have always wondered about this. I mostly try to compare my A1c to my previous A1cs...

I measure my blood sugar 15-20 times a day and I would be surprised if I am missing highs. I hardly saw numbers above 140 for 3 months and I was still above 6 with my A1c.

Jennifer, don't "kill" for such a good A1c number. It's merely luck, not virtue, just like being thin is luck, not virtue! I am grateful every day that I'm a low glycator, and that my BGs are usually in a reasonably reasonable range. That's luck, too. If I could share my luck, I would!

I'm sure you try a lot harder than I do -- but effort is not the whole ballgame. You do your best, but you have to play the cards you're dealt.

I could not relate to a woman in our therapy group, who has an income at least 3 or 4 times as much as I do, who constantly complained that she didn't have enough money. But my psychologist says, and I believe him, that it's a matter of perspective. For her, not being able to buy another piece of jewelry, or another pair of shoes is a hardship. Me, I have 3 pairs of shoes, including a pair of hiking boots, and that's it. And I don't buy jewelry at all. So I'm trying to understand her perspective, hard as it is. I really don't know if she would understand mine, but I'm trying to be an empathic, non-judgmental human being. That's the best way I know of to show support, because I can't change things, but I do care.

Hugs, Natalie ._c-

Perhaps WOT but re the $$ complaints, sometimes there are things like being upside down on their house that can really brutalize people's psyches that may not be apparent? Of course, if one hadn't conspicuously consumed before the 'crashe(s)', one might not be in that situation in the first place but income is no guarantee of financial tranquility.

Perhaps it's similar to BG though, in that financial concerns are almost always there?

I have struggled with on going inconsistencies between my A1c and my meter readings. My medical team admits there is a difference, but has no clue. My A1c readings are however consistent, and generally, if my meter shows improvement, it is reflected in the A1c. My last endo admitted the A1c was "off" and started a routine of ordering the fructosamine test as an additional check. There aren't the strict reference ranges and targets for the fructosamine which makes it more difficult to use as a guide for treatment. Between all the testing, A1c, fuctosamine and my meter readings, I feel like I have a good idea of what is going on.

The other issues which has been brought up is that the ADA has now taken the position that the A1c should be used for diagnosis of diabetes. Given the errors in the A1c test, the Washington Post raised questions about it's use. They focused on the lack of standardization, but the variation noted in this thread is perhaps a bigger concern. My concern is that the A1c, like the fasting glucose is a lagging indicator of diabetes. And the ADA itself failed to differentiate between a "screening" and a "diagnostic" technique. I have no problem with using the A1c as a screening test, it is better than nothing. But it is useless as a diagnostic test, and that is why the AACE has disagreed. In fact, for proper diagnosis, I've come to believe that the Oral Glucose Tolerance Test is much more effective for type 2 diagnosis. But in fact, almost nobody orders an OGTT today. But the tide may be turning, the ADA has now come out and called for the use of the OGTT for all pregnant women.

You are right, my post might have come across a bit harshly (plus yesterday morning I woke up at 21.3 mmol/L due to a failing pump site so may have been overly frustrated!). I try to emphathize with others, I think it’s just that in an environment where people run around saying you will get complications if your A1c is higher than 5 or 6% it gets frustrating sometimes when that seems like an impossible goal (especially when I myself am a perfectionist and feel like I’m just not trying hard enough!). Of course this was the whole intent of your post … Your numbers are interesting and are a reason I wrote in another post (I think, or maybe it was this one) that I find it much more useful to see others’ daily numbers rather than their A1c. I have compared daily numbers with an online Type 1 friend via our blog for about two years now and even though we have very similar control, her A1c is always 0.5 - 1% lower than mine. I love sharing numbers, though, as neither of us judges, sometimes we comment but it is never judgemental.

I read the Washington Post article, and it's only talking about at-home A1c tests, not the lab tests that most of us get. My objection to using the A1c for diagnosis is that low-glycators won't be diagnosed promptly, and will thus be subject to high BGs for a long time until they get sick enough to raise their A1c to a diagnosable level.

Case in point: If I could take my 1991 self, and transport it to 2010, I would have had a 138 fasting BG in June, and a 131 in September -- clearly diagnosable by today's standards. But in November, I would have had an A1c of 4.8, very clearly NORMAL by the proposed diagnostic use of the A1c. So who wins? Would I rather delay the diagnosis (and run out and shop for health and life insurance!) or do I want the early diagnosis, so as to delay or prevent complications?

As it was, and maybe fortunately, my diabetes progressed fairly rapidly (compared with Type 2's; slowly compared with Type 1's), and I was on insulin within 21 months of my PROBABLE diagnosis, and 5 months of my FORMAL diagnosis. But most Type 2 low glycators will not be so lucky.

I'm glad to hear that the AACE is against it -- I never had an OGTT, but wish I had -- the uncertainty and fear of those first 2 years was awful!

Living with diagnosed diabetes since Jan . 1983 . I have asked the question( numerous times ) why are my A1C's higher , than my average finger pokes, CGMS numbers, which would make me think , that the number should be lower. I have no known complications ...my aim is to keep the A1C results a steady outcome ( and will CHEER from joy , if the number comes down next A1C test ) .Do I glycate ( Hi or Low ) or not is the question ?

At the moment, it appears, that Apidra insulin , using since July 2010 , the 8 mm Sure-T's infusion sets WORK for this girl