Hemoglobin A1C Test

Why am I having this test?

You may have the hemoglobin A1C test (A1C test) done to:

Evaluate your risk for developing diabetes (diabetes mellitus).
Diagnose diabetes.
Monitor long-term control of blood sugar (glucose) in people who have diabetes and help make treatment decisions.

This test may be done with other blood glucose tests, such as fasting blood glucose and oral glucose tolerance tests.

What is being tested?

Hemoglobin is a type of protein in the blood that carries oxygen. Glucose attaches to hemoglobin to form glycated hemoglobin. This test checks the amount of glycated hemoglobin in your blood, which is a good indicator of the average amount of glucose in your blood during the past 2–3 months.

What kind of sample is taken?

A health care provider inserting a needle to take blood from a patient's arm.

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel.

Tell a health care provider about:

All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
Any blood disorders you have.
Any surgeries you have had.
Any medical conditions you have.
Whether you are pregnant or may be pregnant.

How are the results reported?

Your results will be reported as a percentage that indicates how much of your hemoglobin has glucose attached to it (is glycated). Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

Adult or child without diabetes: 4–5.6%.
Adult or child with diabetes and good blood glucose control: less than 7%.

What do the results mean?

If you have diabetes:

A result of less than 7% is considered normal, meaning that your blood glucose is well controlled.
A result higher than 7% means that your blood glucose is not well controlled, and your treatment plan may need to be adjusted.

If you do not have diabetes:

A result within the reference range is considered normal, meaning that you are not at high risk for diabetes.
A result of 5.7–6.4% means that you have a high risk of developing diabetes, and you have prediabetes. Prediabetes is the condition of having a blood glucose level that is higher than it should be but not high enough for you to be diagnosed with diabetes. Having prediabetes puts you at risk for developing type 2 diabetes. You may have more tests, including a repeat A1C test.
Results of 6.5% or higher on two separate A1C tests mean that you have diabetes. You may have more tests to confirm the diagnosis.

Abnormally low A1C values may be caused by:

Pregnancy.
Severe blood loss.
Receiving donated blood (transfusions).
Low red blood cell count (anemia).
Long-term kidney failure.
Some unusual forms (variants) of hemoglobin.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

When will my results be ready?
How will I get my results?
What are my treatment options?
What other tests do I need?
What are my next steps?

Summary

The A1C test may be done to evaluate your risk for developing diabetes, to diagnose diabetes, and to monitor long-term control of blood sugar (glucose) in people who have diabetes and help make treatment decisions.
Hemoglobin is a type of protein in the blood that carries oxygen. Glucose attaches to hemoglobin to form glycated hemoglobin. This test checks the amount of glycated hemoglobin in your blood, which is a good indicator of the average amount of glucose in your blood during the past 2–3 months.
Talk with your health care provider about what your results mean.

This information is not intended to replace advice given to you by your health care provider. Make sure you discuss any questions you have with your health care provider.