HbA1c

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HbA1c is a test that measures the amount of glycated hemoglobin in your blood. Glycated hemoglobin is a substance in red blood cells that is formed when blood sugar (glucose) attaches to hemoglobin.

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

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 germ-killing medicine (antiseptic). The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.

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Next, the health care provider gently inserts a needle into the vein. The blood collects into an airtight vial or tube attached to the needle. The elastic band is removed from your arm. 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, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

No special preparation is necessary.

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.

Your doctor may order this test if you have diabetes. It is used to measure your blood sugar control over several months. It can give a good estimate of how well you have managed your diabetes over the last 2 or 3 months.

You have more glycated hemoglobin if you have had high levels of glucose in your blood. In general, the higher your HbA1c, the higher the risk that you will develop problems such as:

• Eye disease
• Heart disease
• Kidney disease
• Nerve damage
• Stroke

This is especially true if your HbA1c remains high for a long period of time.

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

Review Date: 05/02/2009
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.