What does the medical abbreviation A1c mean?

A1c, also known as hemoglobin A1c or HbA1c, is a blood test that measures the average blood sugar level over the past 2-3 months. It is used to diagnose and monitor diabetes. A1c levels are reported as a percentage of total hemoglobin. The higher the A1c level, the higher the average blood sugar level has been over the past 2-3 months.