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January 15, 2003

A1c (Glycohemoglobin, HgbA1c)

Question from Pontiac, Illinois, USA:

I am 22, have had type 2 diabetes treated with Glucophage [metformin] and Actos [pioglitazone] for a couple of years, and when I check my glucose levels at home, my sugars are always well above where they should, regardless of my diet that day. However, my A1c is always well within range. (i.e., my most current one was 6.7%). I was always under the impression that of the two means of monitoring, the A1c was more accurate so I purchased another glucose machine to doublecheck my readings, but so far, they have consistently been the same with that machine. What do you think the cause might be? What actions can I take to prevent it?


I’d check your meter against the lab to make sure it is accurate and your technique is correct. I’d also check the normal range of hemoglobin A1c in your lab because 6.7% would be above normal in many labs. If you a carrier of the trait for sickle cell disease or a similar blood cell disorder call C disease, some tests used to measure A1c give false low results if you are a carrier for either disorder.

Additional comments from Dr. Tessa Lebinger:

You either need more medication or insulin if your blood glucose readings are consistently elevated. Many people diagnosed with type 2 diabetes really have slow onset type 1, thus more insulin deficiency than is possible to treat only with pills. With longer duration of type 2 diabetes, there is also less insulin produced by the pancreas as well. A1c levels only provide an overall average. If you have spikes of blood glucose readings, then the A1c sometimes looks lower than the actual blood glucose levels. You’ve done good detective work to prove that the meters are consistent with each other so this is not likely a problem with the blood glucose data. You should make sure there is no anemia or other problems interfering with A1c tests causing a falsely low A1c level. Another test called fructosamine can also be used for more short term glycemic control analysis compared to A1c levels. Go back and discuss this with your diabetes team and see if they can help you figure all this out.