NBME Form 13 Practice Test

HbA1c reflects average blood glucose over roughly 2 to 3 months because glycated hemoglobin accumulates as red blood cells circulate, and their lifespan is about 120 days. As older cells are replaced, the HbA1c level integrates glucose exposure across that circulating period, giving a picture of long-term glycemic control rather than short-term fluctuations. Keep in mind that factors altering red blood cell turnover (like certain anemias or hemolysis) can affect the reading.