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Home Your Health Multimedia Encyclopedia HbA1c

HbA1c

Definition

HbA1c is a test that measures the amount of glycated hemoglobin in your blood. Your doctor may order this test if you have diabetes.

Alternative Names

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

How the test is performed

Blood is drawn from a vein. The vein is usually on the inside of your elbow or the back of your hand. A nurse will clean the site for germs. The nurse then wraps an elastic band around the upper arm. This puts pressure on the area and makes the vein swell with blood.

Next, the needle is gently inserted into your 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. Then the area 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, or onto a slide or test strip. A bandage may be placed over the area if there is any bleeding.

How to prepare for the test

No special preparation is needed.

How the test will feel

When the needle is inserted, you may feel a slight pinch or some stinging. Afterward, there may be some throbbing.

Why the test is performed

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.

The test may also be used to screen for diabetes.

You have more glycated hemoglobin if you have had high levels of sugar in your blood. In general, the higher your test result is, the higher the risk that you will develop problems. You could develop eye or heart disease. Uncontrolled diabetes can also lead to kidney disease, nerve damage, or stroke.

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

The closer your level is to normal, the less risk you have for these problems.

Normal Values

An HbA1c of 6% or less is normal.

If your it is above 6.5%, you may be diagnosed with diabetes.

If you have diabetes, try to keep your level at or below 7%. But you and your health care provider must decide what a normal level is for you.

Talk with your doctor about the meaning of your test results.

What abnormal results mean

Abnormal results mean that your blood glucose levels have been above normal over weeks to months.

If your level is above 7%, your diabetes control may not be as good as it should be.

High values mean you are at greater risk of problems from having diabetes. If you can bring your level down, you lower your chances of long-term complications.

Ask your doctor how often you should have your level tested. Usually, doctors recommend testing every 3 or 6 months.

What the risks are

Getting a blood sample from some people may be more difficult than from others.

Other risks linked with having blood drawn are slight. Some are excessive bleeding, fainting, bruising, or infection.

References

International Expert Committee Report on the Role of the A1C Assay in the Diagnosis of Diabetes. Diabetes Care. July 2009 32:1344-1345.

American Diabetes Association. Standards of medical care in diabetes--2010. Diabetes Care. 2010 Jan;33 Suppl 1:S11-61.