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URL of this page: https://medlineplus.gov/lab-tests/hemoglobin-a1c-hba1c-test/

Hemoglobin A1C (HbA1c) Test

What is a hemoglobin A1C (HbA1C) test?

A hemoglobin A1C (HbA1C) test is a blood test that shows what your average blood sugar (glucose) level was over the past two to three months.

Glucose is a type of sugar in your blood that comes from the foods you eat. Your cells use glucose for energy. A hormone called insulin helps glucose get into your cells. If you have diabetes your body doesn't make enough insulin, or your cells don't use it well. As a result, glucose can't get into your cells, so your blood sugar levels increase.

Glucose in your blood sticks to hemoglobin, a protein in your red blood cells. As your blood glucose levels increase, more of your hemoglobin will be coated with glucose. An A1C test measures the percentage of your red blood cells that have glucose-coated hemoglobin.

An A1C test can show your average glucose level for the past three months because:

  • Glucose sticks to hemoglobin for as long as the red blood cells are alive.
  • Red blood cells live about three months.

High A1C levels are a sign of high blood glucose from diabetes. Diabetes can cause serious health problems, including heart disease, kidney disease, and nerve damage. But with treatment and lifestyle changes, you can control your blood glucose levels.

Other names: HbA1C, A1C, glycohemoglobin, glycated hemoglobin, glycosylated hemoglobin

What is it used for?

An A1C test may be used to screen for or diagnose:

  • Type 2 diabetes. With type 2 diabetes your blood glucose gets too high because your body doesn't make enough insulin to move blood sugar from your bloodstream into your cells, or because your cells stop responding to insulin.
  • Prediabetes. Prediabetes means that your blood glucose levels are higher than normal, but not high enough to diagnosed as diabetes. Lifestyle changes, such as healthy eating and exercise, may help delay or prevent prediabetes from becoming type 2 diabetes.

If you have diabetes or prediabetes, an A1C test can help monitor your condition and check how well you've been able to control your blood sugar levels.

Why do I need an HbA1C test?

The Centers for Disease Control (CDC) recommends A1C testing for diabetes and prediabetes if:

  • You are over age 45.
    • If your results are normal, you should repeat the test every 3 years.
    • If your results show you have prediabetes, you will usually need to be tested every 1 to 2 years. Ask your provider how often to get tested and what you can do to reduce your risk of developing diabetes.
    • If your results show you have diabetes, you should get an A1C test at least twice a year to monitor your condition and treatment.
  • You are under 45 and are more likely to develop diabetes because you:

You may also need an A1C test if you have symptoms of diabetes, such as:

  • Feeling very thirsty
  • Urinating (peeing) a lot
  • Losing weight without trying
  • Feeling very hungry
  • Blurred vision
  • Numb or tingling hands or feet
  • Fatigue
  • Dry skin
  • Sores that heal slowly
  • Having more infections than usual

What happens during an A1C test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for an A1C test.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

A1C results tell you what percentage of your hemoglobin is coated with glucose. The percent ranges are just a guide to what is normal. What's normal for you depends on your health, age, and other factors. Ask your provider what A1C percentage is healthy for you.

To diagnose diabetes or prediabetes, the percentages commonly used are:

  • Normal: A1C below 5.7%
  • Prediabetes: A1C between 5.7% and 6.4%
  • Diabetes: A1C of 6.5% or higher

Providers often use more than one test to diagnose diabetes. So, if your test result was higher than normal, you may have another A1C test or a different type of diabetes test, usually either a fasting blood glucose test or an oral glucose tolerance test (OGTT).

If your A1C test was done to monitor your diabetes, talk with your provider about what your test results mean.

Learn more about laboratory tests, reference ranges, and understanding results.

Is there anything else I need to know about an HbA1C test?

The A1C test is not used to diagnose gestational diabetes or type 1 diabetes.

Also, if you have a condition that affects your red blood cells, such as anemia or another type of blood disorder, an A1C test may not be accurate for diagnosing diabetes. Kidney failure and liver disease can also affect A1C results. In these cases, your provider may recommend different tests to diagnose diabetes and prediabetes.

References

  1. American Diabetes Association [Internet]. Arlington (VA): American Diabetes Association; c1995–2022. Understanding A1C: A1C does it all; [ cited 2022 May 17]; [about 5 screens]. Available from: https://www.diabetes.org/diabetes/A1C
  2. American Diabetes Association [Internet]. Arlington (VA): American Diabetes Association; c1995–2022. Common Terms; [cited 2022 May 17]; [about 57 screens]. Available from: https://diabetes.org/about-diabetes/common-terms
  3. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Testing for Diabetes and Prediabetes: A1C; [reviewed 2021 Aug 10; cited 2022 May 17]; [about 4 screens]. Available from: https://www.cdc.gov/diabetes/diabetes-testing/prediabetes-a1c-test.html
  4. Centers for Disease Control and Prevention [Internet]. Atlanta: U.S. Department of Health and Human Services; Diabetes Risk Factors; [reviewed 2022 Apr 5;cited 2022 May 17]; [about 3 screens]. Available from: https://www.cdc.gov/diabetes/risk-factors/
  5. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2022. A1c test; [cited 2022 May 17]; [about 7 screens]. Available from: https://www.mayoclinic.org/tests-procedures/a1c-test/about/pac-20384643
  6. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2022. Diabetes Mellitus (DM); [modified 2020 Sep; cited 2022 May 17]; [about 13 screens]. Available from: http://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/diabetes-mellitus-dm-and-disorders-of-blood-sugar-metabolism/diabetes-mellitus-dm#v773034
  7. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests; [updated 2022 Mar 24; cited 2022 May 17]; [about 8 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
  8. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Diabetes Tests & Diagnosis; [reviewed 2016 Dec; cited 2022 May 17]; [about 6 screens]. Available from: https://www.niddk.nih.gov/health-information/diabetes/overview/tests-diagnosis#who
  9. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; The A1C Test & Diabetes; [reviewed 2018 Apr; cited 2022 May 17]; [about 10 screens]. Available from: https://www.niddk.nih.gov/health-information/diagnostic-tests/a1c-test#affected
  10. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Insulin Resistance & Prediabetes; [reviewed 2018 May; cited 2022 May 17]; [about 8 screens]. Available from: https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes/prediabetes-insulin-resistance#develop
  11. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What is Diabetes?; [reviewed 2016 Dec; cited 2022 May 17]; [about 4 screens]. Available from: https://www.niddk.nih.gov/health-information/diabetes/overview/what-is-diabetes#types
  12. Testing.com [Internet]. Seattle (WA).: OneCare Media; c2022. Hemoglobin A1c; [modified 2021 Nov 9; cited 2022 May 17]; [about 12 screens]. Available from: https://www.testing.com/tests/hemoglobin-a1c/
  13. Testing.com [Internet]. Seattle (WA).: OneCare Media; c2022. Glucose Testing; [modified 2021 Nov 9; cited 2022 May 17]; [about 11 screens]. Available from: https://www.testing.com/glucose-testing/
  14. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: A1C; [cited 2022 May 17]; [about 4 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=A1C
  15. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2022. Glycohemoglobin (HbA1c, A1c); [current 2021 Jul 28; cited 2022 May 17]; [about 8 screens]. Available from: https://patient.uwhealth.org/healthwise/article/en-us/hw8432

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.