Hemoglobin A1c; HbA1c; glycosylated hemoglobin; glycohemoglobin; Glycated hemoglobin
A1C is a blood test used to screen people to find out whether they have diabetes or prediabetes. It's also used in people who know they have diabetes to measure how well they are controlling their blood sugar and to guide their treatment decisions over time.
You may need this test to check for prediabetes or diabetes. If you already know that you have diabetes or prediabetes, you may need this test to see how well you are controlling your blood sugar.
People with diabetes must track their blood sugar (glucose) levels every day to make sure they aren’t too high or too low. The A1C test gives results for a longer period of time. It shows whether your blood sugar has been too high on average in the previous two to three months. When blood sugar is high, more glucose builds up and sticks to your hemoglobin, a protein that carries oxygen in red blood cells. The A1C test measures the percentage of hemoglobin that is coated with blood sugar.
Depending on the type of diabetes you have, how well it's controlled, and your health care provider’s preferences, you may need to have the A1C test two or more times a year. The American Diabetes Association (ADA) recommends that you have an A1C test at least twice a year if you are meeting your blood sugar goals and your blood sugar is well-controlled. If you aren’t meeting your goals or your medication has changed lately, you should have the A1C test more often. You also may have the test when your health care provider first starts working with you to treat your diabetes.
If your health care provider is testing you for diabetes, you may also take a fasting plasma glucose test, or FPG, or an oral glucose tolerance test, or OGTT, as part of your screening and diagnosis. You may also be tested for sugar, ketones or protein in the urine.
Laboratory test results may vary depending on your age, gender, health history, the method used for the test, and many other factors. If your results are different from the results suggested below, this may not mean that you have a problem. Ask your health care provider to explain what the results mean for you.
A1C is reported as a percentage:
Normal A1C is considered to be below 5.7 percent. Results between 5.7 and 6.4 percent may mean you have prediabetes. This means you have a higher risk of developing diabetes.
Results of 6.5 percent or higher on two separate occasions may mean that you have diabetes.
The ADA recommends that people with diabetes should maintain an A1C below 7 percent. The American Association of Clinical Endocrinologists recommends an A1C of 6.5 percent or less. Recommendations may vary based on the person's age, medical conditions, or other factors.
The test requires a blood sample, which is drawn through a needle from a vein in your arm.
Taking a blood sample with a needle carries risks that include bleeding, infection, bruising, and a sense of lightheadedness. When the needle pricks your arm, you may feel a slight stinging sensation or pain. Afterward, the site may be slightly sore.
Your blood sugar levels usually vary throughout the day. These variations won't affect the A1C.
If you have sickle cell anemia or other blood disorders, a standard A1C test may be less useful for diagnosing or monitoring diabetes. (Your health care provider may be able to find another diabetes test that will better serve you.) In addition, the test results may be skewed if you have anemia, heavy bleeding, an iron deficiency, kidney failure, or liver disease.
You don't need any special preparation for the test.