Overview
The A1C test is a common blood test for diagnosing diabetes. For people living with diabetes, the test checks how well they manage blood sugar levels. The A1C test also is called the glycated hemoglobin, glycosylated hemoglobin, hemoglobin A1C or HbA1c test.
An A1C test result shows the average blood sugar level over the past 2 to 3 months. The A1C test measures what percentage of hemoglobin in the blood is coated with sugar, also called glycated.
The higher the A1C level is, the poorer the blood sugar management. And the higher the risk of having health concerns related to diabetes.
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Why it's done
The results of an A1C test can help a healthcare professional:
- Diagnose prediabetes. If you have prediabetes, you have a higher risk of getting diabetes and cardiovascular disease.
- Diagnose diabetes. To confirm a diabetes diagnosis, your healthcare professional may look at the results of two blood tests. These can be either two A1C tests or the A1C test plus another test, such as a fasting blood sugar test, also called blood glucose test.
- Check your diabetes treatment plan. The result of a first A1C test also gives you a starting A1C level. It's compared to future A1C test results to see how well your diabetes treatment plan is working.
How often you need an A1C test depends on the type of diabetes, your treatment plan, your treatment goals and what your healthcare professional decides. For example, you may have an A1C test:
- Once every year if you have prediabetes.
- Twice a year if you don't use insulin and your blood sugar level stays within your target range.
You may need A1C tests more often if you use insulin or if have trouble keeping your blood sugar level within your target range. You also may have A1C tests if your healthcare professional changes your diabetes treatment plan or you begin taking a new diabetes medicine.
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How you prepare
The A1C test is a simple blood test. You don't need to fast for the A1C test. So you can eat and drink as usual before the test.
What you can expect
During the A1C test, a member of your healthcare team takes a blood sample by putting a needle into a vein in your arm or pricking your finger with a small, pointed tool.
Blood taken from a vein goes to a lab for testing. Your healthcare team may look at blood from a finger prick for results right away. You have this in-office test only to check on your treatment plan. You won't have it for diagnosis or screening.
Results
A1C test results appear as a percentage. A higher A1C percentage means higher average blood sugar levels. Results are as follows:
- Below 5.7% is healthy.
- A result of 5.7% to 6.4% means prediabetes.
- A result of 6.5% or higher on two separate tests means diabetes.
For most adults living with diabetes, an A1C level of less than 7% is a common treatment target. Some people may have lower or higher targets.
The target of less than 7% is linked to a lower risk of health concerns related to diabetes, also called complications. If your A1C level is above your target, your healthcare team may suggest a change in your diabetes treatment plan.
A1C and self-monitoring
Part of a diabetes treatment plan includes using a blood glucose meter or other device to check blood sugar at home. Your healthcare team tells you how often and when to test your blood sugar.
Self-monitoring devices show blood sugar levels in milligrams of sugar per deciliter (mg/dL) or millimoles of sugar per liter (mmol/L). The device measures your blood sugar level at the time you do the test. So the results may change throughout the day. The change depends on eating, exercise, stress and other factors.
Checking your blood sugar helps you make choices about diet, exercise and daily treatment goals. It also helps you know if you're meeting your A1C target. For example, if your A1C target is below 7%, self-monitoring blood sugar levels should be, on average, below 154 mg/dL (8.6 mmol/L).
A1C test results typically go along with the following results of tests for blood sugar levels:
| A1C level |
Estimated average blood sugar (glucose) level |
| 6% |
126 mg/dL (7 mmol/L) |
| 7% |
154 mg/dL (8.6 mmol/L) |
| 8% |
183 mg/dL (10.2 mmol/L) |
| 9% |
212 mg/dL (11.8 mmol/L) |
| 10% |
240 mg/dL (13.4 mmol/L) |
| 11% |
269 mg/dL (14.9 mmol/L) |
| 12% |
298 mg/dL (16.5 mmol/L) |
Limitations of the A1C test
Some factors may make A1C test results less exact. These include:
- Pregnancy.
- Recent or heavy blood loss.
- Recently receiving blood from a donor, called a transfusion.
- Sometimes, a condition that results in not having enough red blood cells, called anemia.
- Certain blood conditions, such as sickle cell anemia.
- Other forms of hemoglobin in the body.
Hemoglobin is a protein that carries oxygen through the blood. The most common form of hemoglobin protein is called hemoglobin A. If there are other forms of hemoglobin in the blood, called variants, the A1C test results may not be right. Hemoglobin variants are more common among people of African, Mediterranean or Southeast Asian descent.
If you have a hemoglobin variant, your test may need to go to a special lab. Or you may need another test to diagnose diabetes and check on its treatment.
Feb. 22, 2025