Saturday, February 26, 2011

A1c and Iron

Sigh. It's happened again. I set up an experiment and then something beyond my control made the results meaningless.

That often seems to happen. I'm doing a test that requires measuring blood glucose (BG) at a specific time, and just as I'm about to do so, the phone rings, and it's an important call I can't ignore. Or I want to compare BG control on two consecutive days, do a whole slew of tests on day 1 and then on day 2 come down with the flu, which makes any BG measurements useless.

I've always had A1c levels that seem to be higher than what I'd expect on the basis of my BG readings. Because of this, I even spent more than $500 on continuous glucose monitor sensors (a kind friend gave me the meter) to make sure I wasn't going high at some unexpected time when I wasn't measuring.

I wasn't. The results were what I'd expect. Fastings were 70 to 90, and going over 130 was rare. But my A1c was always around 6, which calculates to an average BG of 130, which means I'd be going way over 130 a lot of the time to balance the lower fastings.

I tested my two different meters (Ultra and Freestyle), and they agreed quite well with each other and with my hospital lab.

I know there's some individual variation in red blood cell (RBC) lifetimes, and an increased lifetime could raise A1c, because the longer a RBC has been in your body, the more likely it is to be glycated.

So when I read, as reported here, that low iron can make your A1c higher than it should be, I decided to try taking iron-containing multivitamins a couple of weeks before my next A1c. I usually use iron-free vitamins, because iron can contribute to cardiac problems, and people with diabetes are at increased risk of that.

The theory is that if you're iron-deficient, you won't produce reticulocytes, or new RBCs, as fast as you should, so your body will let the older, more-glycated RBCs live longer. If you take iron, you'll produce more new, glycation-free RBCs, so your A1c will be lower.

I did the test, and the results seemed to confirm the theory. My A1c dropped to 5.3, which is about what I'd expect.

But then I read the fine print. Apparently the A1c machine at the local hospital had broken, so they sent all the samples to the Mayo Clinic. So was the lower A1c because of the iron? Or was it because Mayo was using a different type of test that gave different results. I didn't know.

So I did the test again. Two weeks before I gave blood, I switched to the iron-containing vitamins. This time the A1c, done at my local hospital, was 5.4.

I called the hospital lab to make sure they were still using the high-performance liquid chromatography method they'd used before. This is supposed to be the best method because it's the one used in the famous DCCT trials.

They weren't. They'd changed methods to an immunoassay. So was the result this time because of the iron? Or was it because of a different method?

I don't know. I'll have to do it all over again. I don't get labwork every three months, more like six, because it's a pain and the results are usually pretty much the same. So maybe by the time I get this resolved I'll be living in a nursing home. Who knows.

It's just one of the many frustrations of having diabetes.

On the other hand, being able to test things is one of the fun things about having diabetes. With so many other diseases, we have to let the medical people do all kinds of arcane tests and procedures. I don't know of a home MRI machine, or a home "put in your own coronary stent" kit, for example.

If I ever resolve this issue, I'll post here about it.


  1. On the third hand, you could just be a high glycator, the opposite of me. (Reference: FAQ on When I had my coma, I had an A1c of 10.7, which translates to an eaG of 260. NO WAY!! I was running 400's and 500's for months before it happened.
    I'm also curious whether you've had your ferritin measured -- that could give you some idea of where you stand as to iron.
    Always enjoy your columns! :-)
    Natalie ._c-

  2. Yes, high glycation is another possibility. Then one needs to find out if high glycation on hemoglobin equates to high glycation on other compounds. And they need to determine if complications relate more to A1c or to actual BG.

    Joslin is currently studying why some people get complications and others don't.

    In my case, high glycation wouldn't explain why the number dropped to 5.3 with iron plus different lab.

    Yes, I had ferritin measured, and it was on the low end of normal, which is why I decided to do the iron test. At least I don't have hemochromatosis.

  3. I vaguely remember Dr Eades recommending that diabetics should donate blood regularly to control their usually high iron levels! (My copy's out on loan at the moment, so I can't check.) What an interesting disease we have... Hope you get a good run at the next experiment, Gretchen!

    (btw, my diabetic shelves are bare atm as a result of another newbie being given appalling information - yours was the first book I handed her, to calm her down...)

  4. Nicky, People with diabetes don't necessarily have high iron. Just those with hemochromatosis, which can cause diabetes.

  5. Did you ever figure this out? I'm new to your blog, so still browsing the posts - sorry if I missed it.

  6. No. I gave up. I also recently started thyroid, which can also affect BG, so I'd have to do the whole experiment over again.

  7. In case you're still checking this...A1C of 6 means average BG around 100, which seems in line with your readings. Don't know where you saw 6=130, I think that's what caused your confusion.

  8. Anonymous, There are different formulas for calculating average BG according to A1c. Bernstein uses the number 130. This site

    gives a formula that works out to 126. Other formulas come up with other numbers.