HbA1c

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HbA1c

Definition:

HbA1c is a test that measures the amount of glycosylated hemoglobin in your blood. The test gives a good estimate of how well diabetes is being managed over time.

Alternative Names:

Glycosylated hemoglobin; Hemoglobin - glycosylated; A1C; GHb; Glycohemoglobin; Diabetic control index

How the test is performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell with blood.

A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.

In infants or young children: The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test:

No special preparation in necessary. You do not need to fast (stop eating).

How the test will feel:

When the needle is inserted to draw blood, you may feel moderate pain, or only a prick or stinging sensation. Afterward, there may be some throbbing.

Why the test is performed:

This test measures blood sugar control over an extended period in people with diabetes. In general, the higher your HbA1c value, the higher the risk that you will develop problems such as eye disease, kidney disease, nerve damage, heart disease, and stroke. This is especially true if your HbA1c remains elevated on more than one occasion.

The closer your HbA1c value is to normal, the less risk you have for these complications.

Normally, only a small percentage of the hemoglobin (Hb) molecules in red blood cells become glycosylated (that is, chemically linked to glucose). The percent of glycosylation increases over time, and is higher if there is more glucose in your blood. Therefore, older red blood cells will have a greater percent of glycosylated hemoglobin, and diabetics whose blood glucose has been too high will have a greater percent of glycosylated hemoglobin.

Review Date: 8/1/2005
Reviewed By: Nikheel S. Kolatkar, MD, Clinical and Research Fellow, Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Harvard Medical School, Boston, MA. Review provided by VeriMed Healthcare Network.

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