May 28, 1999
A1c (Glycohemoglobin, HgbA1c)
Question from Israel:
I am a 28 year old diabetic patient (type 1). In order to achieve good control one must have a near normal HbA1c (which I do). But, HbA1c reflects only the mean glucose level during the past three months (i.e., HbA1c of all-month peaks of glucose (30 –> 370) would be the same as all-month glucose level of 200 mg/dl). Therefore it is not enough for good glucose control. Is there another parameter one can use to check if his glucose levels are not varying too much (i.e., standard deviation)?
You are absolutely right, it is not only the mean blood sugar that matters (as represented by the A1c), but the standard deviation too. However the latter calculation is almost never done: first, because most people would not know how to do it, and second, because achieving a near normal A1c is considered a sufficient achievement. I expect that when the GlucoWatch and the Minimed sensors come into increasing use sometime next year that a lot more attention will be paid to the more detailed analysis of the greatly increased amount of information: e.g., 70 blood sugars a day on the GlucoWatch and many more with the MiniMed sensor. Ultimately I expect that this sort of information will be fed reliably directly into a pump control to complete a closed loop system and no patient calculation will be needed!