Ask the Diabetes Educator Archive

8/8/05

Q:
My doctor tells me to fast before my A1C test. The lab taking the samples says it doesn't matter. Since I can only supply samples during the afternoon because of my work schedule, the fasting is a problem with no breakfast or lunch for that day.

A:
No fasting is required for an A1C test, as this is an average measurement, not what's relevant for that day. What the resulting numbers reflect are blood sugars over the preceding 2.5 - 3 months at different percent rates. The preceding month's testing numbers contribute to 50% of the A1C number, the remaining 50% divided between the 2 months preceding that. In most cases, consistency in lifestyle habits will have the percentages in closer range to one another.