Glycosylated Hemoglobin Test (Hemoglobin A1c)

Say: gly-KOH-sih-lay-tid HEE-muh-glow-bin

This blood test can tell someone if their diabetes is under control or out of control. As a person's blood sugar gets higher, glucose attaches to hemoglobin (a substance inside red blood cells that carries oxygen to cells). When this happens, the hemoglobin has become glycosylated. The glucose stays attached to the hemoglobin for the life of the red blood cell, or about 2 to 3 months.

This blood test measures the amount of glycosylated hemoglobin in the blood. In other words, it's a way of figuring out what the person's average blood glucose level was for the 2–3 months before the test. This can help determine how well a person's diabetes is being controlled over time.