Shorthand for hemoglobin A1c or glycosylated hemoglobin, an indicator of blood glucose control over the previous two to three months. Hemoglobin, a protein found in red blood cells, carries oxygen from the lungs to tissues throughout the body. Some of the glucose in the bloodstream can also bind to hemoglobin molecules for the life of the red blood cell, which is about four months. Throughout the life of the red blood cell, the higher the blood glucose level, the more glucose that becomes bound to the hemoglobin in that cell.
The percentage of hemoglobin in a blood sample that is glycosylated (has glucose attached to it) indicates how well blood glucose has been controlled over the previous two to three months. Typically, people who do not have diabetes have an HbA1c value of less than 6%. Based on the results of studies such as the Diabetes Control and Complications Trial, which showed that tight blood glucose control could reduce the risk of diabetic eye, kidney, and nerve disease, the American Diabetes Association (ADA) recommends an HbA1c goal of less than 7% for people with diabetes in general.
How often should people with diabetes have their HbA1c level tested? According to the ADA, people who are meeting their treatment goals and who have stable blood glucose control should get HbA1c testing at least twice a year. People whose treatment has been changed recently or who are not achieving their blood glucose targets should be tested four times a year.