Wednesday, June 18, 2008


I got a phone call a few days ago about my labwork. The nurse said it was "perfect." Since they won't give the actual numbers over the phone, I didn't say anything, but I had my doubts. Anyway, my cholesterol was excellent now (although my HDL was lower), which is great. Last time I was in the normal range, but just out of the diabetic range, if you know what I mean. My A1c was much like last time: abnormally low. I don't know why this has been happening, just for the last year. The endo didn't seem too concerned about it, since we know what my A1c *should* be, and that's not really worrying. It's just confusing to other doctors who of course first want to know what my A1c is, and then I have to explain it. Not that I really have an explanation. Anyway, I just read this about donating blood yesterday in the Diabetes In Control Newsletter:

The donation of red cells does indeed have an effect on A1c levels. Since the test measures a type of hemoglobin in the red blood cell that attaches to glucose, the amount of red blood cells in the blood has a direct correlation to A1c levels.

We already know that patients who have a high turnover in red blood cells, such as those with sickle cell anemia, have an artificially low A1c, because they are making a higher number of new red blood cells. This is similar to what happens when red cells are lost due to a blood donation. A normal donation may require up to four weeks of new red cell production and a double donation may take eight weeks.

It takes about 8 weeks for new red blood cells to attach to glucose and raise the A1c to pre-donation levels.

A1c levels can actually be decreased by 4 to 8% for the first 4 to 6 weeks after a donation, and if a double donation A1c can be as much as 16% off for even a longer time.

Based on this information it is important to tell your patients that they should have their A1c done just prior to the donation, and more importantly we should ask if they have donated blood when they see us for an appointment.

Information from Practical Diabetology June 2008
Richard Benjamin, MD, CMO American Red Cross Blood Services

I don't donate blood. I don't have anything obvious, like sickle cell. I do have recurring anemia and have to take iron or it comes back, but they've never really found an underlying cause (other than the most obvious one). So it sounds like the problem could be too high turnover of red blood cells? I guarantee I am not secretly running low or anything. If anything it should be higher than any past A1c, just due to progression. Oh, and if I saw this A1c for a Type 1, I wouldn't say it was "perfect" - I'd be quite worried.


Eric Link said...

Hi - I follow your blog and wanted to let you know that our HomeCheck A1c might be something you would like to try. It extensively screens the blood sample for 100's of issues before the A1c is done. It will tell you what is wrong if possible. We can also follow up w/ the lab and find out more about what is going on. You can get one here if you are interested.

Robert said...

I have polycythemia vera for years treated with phlebotomy and Intron-a injections. Dx 1990. Started IFN 1995. Age 60. Recently dx with DM. A1c accuracy affected? GLU elevated on CBCs. No diabetic symptoms but primary says I have multiple classic metabolic syndromes.

Christine-Megan said...

My a1c is always surprisingly low too, but I do donate blood. Even when I don't, it's lower than I expect though.

Lili said...

Eric - Thanks, but I'm not sure how much that would help me, unless it can tell the age of red blood cells.

Robert - I am not a doctor. Maybe you could surf on over to or and post your questions.

Christine - I've heard that at the lower range of A1cs, they tend to be a little lower than they should be. Isn't it weird? Everyone puts so much stock in A1c.