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

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. This puts pressure on the area and makes the vein swell with blood.

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. Then 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 needed.

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

The test may also be used to screen for diabetes.

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.

An HbA1c of 6% or less is normal.

If your HbA1c is above 6.5% you may be diagnosed with diabetes.

If you have diabetes, try to keep your HbA1c level at or below 7%. However, you and your health care provider must decide what a normal HbA1c level is for you.

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

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

If your HbA1c is above 7%, it means that your diabetes control may not be as good as it should be.

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

Ask your doctor how often you should have your HbA1c tested. Usually, doctors recommend testing every 3 or 6 months.

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

Other risks linked with having blood drawn are slight, but may include:

• Excessive bleeding
• Fainting or feeling light-headed
• Hematoma (blood accumulating under the skin)
• Infection (a slight risk any time the skin is broken)

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.