What is the definition or description of: hemoglobin a1c?

Sugar : Hga1c is the average percentage of blood sugar over a 120 day period of time (simplist answer).

Average Blood Sugar: It helps determine the average blood sugar over a long period of time, about 2 or 3 months. See: http://j.Mp/wy0zmc.

Average blood sugar: Hemoglobin a1c is an index. Every day, 1% of human red blood cells are recycled & replaced by new rbcs from the bone marrow. When they are "born, " the hemoglobin inside them takes a snapshot of the blood sugar at that moment. Add up 100 days of sugar readings, and that is the a1c average, which gives physicians an indication of blood sugar control over the previous 3 months to help direct therapy.

Estimate of Sugar: The hemoglobin A1c (now A1c) is a way of estimating someones blood sugar average as if it were being taken continually. Glucose binds to different proteins & Hgb is one of them. All the A1c is, is a percent of the Hgb with glucose attached. This can then be compared to a formula or tables to get an estimated avg glucose. The test is very good, but not perfect or accurate in all patients.