Glycosylated Hemoglobin Test

(HbA1c; GHb; Glycohemoglobin; Diabetic Control Index)


A glycosylated hemoglobin test (HbA1c) is a blood test that measures the percentage of hemoglobin (a protein found in blood red cells) that has attached to glucose. The higher your blood sugar is, the more that glucose gets attached to your hemoglobin.


glucose and RBC
Copyright © Nucleus Medical Media, Inc.

Reasons for Test    TOP

HbA1c shows how high your blood sugar levels have been during the past 3 months. This can help your doctor determine how well you are controlling your diabetes. Your doctor may also use HbA1c to test you for diabetes.

Possible Complications    TOP

There are no major complications associated with this test.

What to Expect    TOP

Description of Test

You will be asked to sit. An area inside your elbow will be cleaned with an antiseptic wipe. A large band will be tied around your arm. The needle will then be inserted into a vein. A tube will collect the blood from the needle. The band on your arm will be removed. After all the blood is collected, the needle will be removed. Some gauze will be placed over the site to help stop bleeding. You may also be given a bandage to place over the site. The process takes about 5-10 minutes.

After Test

Apply pressure to the site until bleeding stops.

How Long Will It Take?    TOP

Less than 5 minutes

Will It Hurt?    TOP

It may hurt slightly when the needle is inserted.

Results    TOP

Talk to your doctor about what goal is right for you. If your HbA1c levels are high, you may need a change in treatment, such as:

  • Changing your medications
  • Increasing your level of physical activity
  • Modifying your diet

Talk with your doctor about when you should be tested again.

Call Your Doctor    TOP

After the test, call your doctor if any of the following occurs:

  • Redness
  • Swelling
  • Persistent bleeding or discharge
  • Pain

If you think you have an emergency, call for emergency medical services right away.


American Diabetes Association
National Diabetes Education Program


Canadian Diabetes Association


American Diabetes Association. Standards of medical care in diabetes—2008. Diabetes Care. 2008;31:S12-S54.
Aronow WS, Ahn C, Weiss MB, Babu S. Relation of increased hemoglobin A1c levels to severity of peripheral arterial disease in patients with diabetes mellitus. Am J Cardiol. 2007;99(10):1468-1469.
Check your hemoglobin A1c IQ. National Diabetes Education Program website. Available at:
...(Click grey area to select URL)
Accessed September 3, 2015.
A new number. American Diabetes Association website. Available at:
...(Click grey area to select URL)
Accessed September 3, 2015.
Pradhan AD, Rifai N, Buring JE, Ridker PM. Hemoglobin A1c predicts diabetes but not cardiovascular disease in nondiabetic women. Am J Med. 2007;120(8):720-727.
Saudek CD, Herman WH, Sacks DB, et al. A new look at screening and diagnosing diabetes mellitus. J Clin Endocrinol Metab. 2008;93(7):2447-2453.
American Diabetes Association. Standards of medical care in diabetes mellitus. Diabetes Care. 2003;26 Suppl 1:S33-S50.
Last reviewed September 2015 by Kim Carmichael, MD
Last Updated: 9/3/2015

EBSCO Information Services is fully accredited by URAC. URAC is an independent, nonprofit health care accrediting organization dedicated to promoting health care quality through accreditation, certification and commendation.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

To send comments or feedback to our Editorial Team regarding the content please email us at Our Health Library Support team will respond to your email request within 2 business days.