HbA1c values reflect average blood glucose over approximately how many months?

• A. About 3 months
• B. About 1 month
• C. About 6 months
• D. About 12 months

Answer: (A)

HbA1c gauges how much glucose has attached to hemoglobin over the lifespan of red blood cells. Since red blood cells live about 120 days, the glycated hemoglobin level builds up reflecting average blood glucose over roughly the last three months. That makes about three months the best estimate for what HbA1c represents. The other timeframes are not aligned with the biology of RBC turnover: one month is too short to show a stable average, while six or twelve months would not match the way HbA1c incorporates glucose exposure over a typical red cell lifespan.