A1c is a lab test that shows the average level of blood sugar (glucose) over the previous 3 months. It shows how well you are controlling your diabetes.
HbA1C test: Glycated hemoglobin test; Glycosylated hemoglobin test; Hemoglobin glycosylated test; Glycohemoglobin test
How the Test is Performed
A blood sample is needed. Two methods are available:
- Blood drawn from a vein (venipuncture
). This is done at a lab.
- Finger stick. This can be done in your health care provider's office. Or you may be prescribed a kit that you can use at home.
How to Prepare for the Test
No special preparation is needed.
How the Test Will Feel
With a finger stick, you may feel slight pain.
With blood drawn from a vein, you may feel a slight pinch or some stinging when the needle is inserted. Afterward, there may be some throbbing.
Why the Test is Performed
Your doctor may order this test if you have diabetes
. It shows how well you are controlling your diabetes.
The test may also be used to screen for diabetes.
The following are the results when A1c is being used to diagnose diabetes:
If you have diabetes, you and your doctor or nurse will discuss the correct range for you. For many people the goal is to keep your level below 7%.
The test result may be incorrect in people with anemia, kidney disease, or certain blood disorders (thalassemia). Talk to your doctor if you have any of these conditions.
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What Abnormal Results Mean
Abnormal results mean that you have had a high blood sugar level over a period of weeks to months.
If your A1c is above 6.5% and you do not already have diabetes, you may be diagnosed with diabetes.
If your level is above 7% and you have diabetes, it often means that your blood sugar is not well controlled. Your target A1c should be determined by you and your health care provider.
The higher your A1c, the higher the risk that you will develop problems such as:
If your A1c stays high for a long period, the risk of these problems is even greater.
Ask your doctor how often you should have your level tested. Usually, doctors recommend testing every 3 or 6 months.
Obtaining a blood sample from some people may be more difficult than from others.
Other risks of having blood drawn are slight, but may include:
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
American Diabetes Association. Standards of medical care in diabetes--2012. Diabetes Care. 2013 Jan;33 Suppl 1:S11-61.
Buse JB, Polonsky KS, Burant CF. Type 2 diabetes mellitus. In: Melmed S, Polonsky KS, Larsen PR, et al., eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 31.
Inzucchi SE, Sherwin RS. Type 2 diabetes. In: Goldman L,Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, Pa: Elsevier Saunders; 2011:chap 237.
Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Bethanne Black, and the A.D.A.M. Editorial Team.