November 29, 2002
Question from Phoenix, Arizona, USA:
How important are postprandial sugars if the A1c is in the acceptable close to 6%? If two people with diabetes were to have the same A1c, but one had vastly varying sugars while the other one had stable sugars, is there an increased risk for the first (i.e., cardiovascular or other risks) excluding hypoglycemia?
For a long time, it has been recognised that a given level of hemoglobin A1c reflected only a mean blood sugar. Thus both a state where there was very little variation and one where the high and low ranges were much greater. There have been no studies that have compared the incidence of complications in two such groups because of the obvious difficulty in getting enough data over sufficient time to correlate the standard deviations with complications. However, the obvious risk of an A1c of between 6 and 7 when there are wide blood glucose fluctuations is not so much the high levels as that of hypoglycemia, especially if there is hypoglycemia unawareness.
Postprandial blood sugars are only indirectly part of this issue. Just as the early morning fasting blood sugar is a good way of calibrating the effectiveness of bedtime Lantus (insulin glargine) in providing basal insulin needs, so the occasional two-hour postprandial value can monitor how effectively the dose of bolus given just after the meal and modified according to the pre-meal blood sugar and the ‘carbs’ consumed is containing blood sugars at this time. Such measurements are of less value when using simpler insulin regimens such as twice-a-day Regular and NPH.