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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

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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.
  • It may also be used to screen for diabetes in high risk people, including:
    • Adults of any age who are overweight or obese (BMI ≥ 25 kg/m²)
    • People who have one or more additional risk factors for diabetes, such as first-degree relative with type 1 diabetes, polycystic ovarian syndrome, or high risk ethnic background
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.


If your HbA1c levels are high and you have never been diagnosed with type diabetes talk to your doctor about what to do next

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—2014. Diabetes Care. 2014 Jan;37 Suppl 1:S14-80.

Diabetes mellitus type 1. Available at: Updated May 31, 2017. Accessed August 29, 2017.

Glycemic control monitoring. Available at: Updated May 31, 2017. Accessed August 29, 2017.

HbA1c measurement. Available at: Updated February 13, 2017. Accessed August 29, 2017.

Last reviewed September 2017 by EBSCO Medical Review Board Michael Woods, MD, FAAP

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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