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Glycosylated Hemoglobin Test

(HbA1c; GHb; Glycohemoglobin; Diabetic Control Index)
  • Definition

    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
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  • Reasons for Test

    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

    There are no major complications associated with this test.
  • What to Expect

    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?
    Less than 5 minutes
    Will It Hurt?
    It may hurt slightly when the needle is inserted.
    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

    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

    Health Canada


    American Diabetes Association. Standards of medical care in diabetes mellitus. Diabetes Care. 2003;26 Suppl 1:S33-S50.

    American Diabetes Association. Standards of medical care in diabetes—2008. Diabetes Care. 2008;31:S12-S54.

    Aronow WS, Ahn C, et al. 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: Accessed September 3, 2015.

    A new number. American Diabetes Association website. Available at: Accessed September 3, 2015.

    Pradhan AD, Rifai N, et al. Hemoglobin A1c predicts diabetes but not cardiovascular disease in nondiabetic women. Am J Med. 2007;120(8):720-727.

    Saudek CD, Herman WH, et al. A new look at screening and diagnosing diabetes mellitus. J Clin Endocrinol Metab. 2008;93(7):2447-2453.

    Revision Information

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