Hemoglobin A1C Testing

Reviewed by: HU Medical Review Board | Last reviewed: October 2020.

The hemoglobin A1C test measures your average blood sugar level over the past 2 to 3 months. The test is also known as:1,2

  • Glycated hemoglobin
  • Glycosylated hemoglobin
  • HbA1c

When glucose (sugar) enters your blood, it sticks to hemoglobin. This is a protein in your red blood cells. It is normal for everyone to have some glucose attached to their hemoglobin. However, people with higher blood glucose levels have more. Doctors use the hemoglobin A1C test to measure what percentage of your red blood cells contain hemoglobin with sugar stuck to them.3

If your hemoglobin A1C level is 6.5 percent or higher, you have diabetes.2,3

Why is hemoglobin A1C testing important?

Higher A1C levels mean that your blood sugar levels are not well controlled and that you are at higher risk for diabetes complications. The hemoglobin A1C test can give you and your doctor important clues about your blood sugar levels. Your doctor might have you take a hemoglobin A1C test if you have any of the common signs of high blood sugar, including:4

  • Blurred vision
  • Frequent infections
  • Numbness or tingling, especially in the legs, feet, arms, and hands
  • Sores or cuts that heal slowly or do not heal
  • Excessive thirst and increased urination
  • Sudden, unexplained weight loss
  • Fatigue
  • Constant hunger

You might also be asked to take an A1C test if you have any of the risk factors for type 2 diabetes, including high blood pressure and being overweight.4

If you have already been diagnosed with type 2 diabetes, your doctor will use this test to see how well you are managing your blood sugar levels. The test provides an average of your blood glucose control over 3 months.3

Higher hemoglobin A1C levels are linked to diabetes complications, so it is important to reach and maintain your specific A1C goal. Your doctor will talk to you about your individual A1C before your test.2,3

How is hemoglobin A1C testing done?

You can have a hemoglobin A1C test done in your doctor’s office or a lab. You do not need to fast, so you can eat and drink normally before the test.1

Before your test tell your doctor about any medicines you are taking, if you are sick, or if you have other health conditions, since these can affect your results.1

At the time of your test, your doctor or a member of your healthcare team will take a sample of your blood. This can be done with a finger prick or needle inserted into a vein in your arm. The results from a finger prick are usually available quickly, but blood taken from a vein will be sent to a lab and it may take a few days for your results.1

What do hemoglobin A1C test results mean?

Your hemoglobin A1C test results will be a percentage, such as an A1C of 7.5 percent. Higher percentages are a sign that your average blood sugar levels are also high.4

The American Diabetes Association uses the following percentages to diagnose prediabetes and diabetes:2

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

If your first test is above normal, your doctor may have you take the test again on a different day to confirm your diagnosis. If 2 or more of your tests are above normal, you will be diagnosed with prediabetes or diabetes.1,4

High A1C levels may be a sign that you need to change your diet, medication, and/or activity level. For many people with type 2 diabetes, a hemoglobin A1C of 7 percent or less is usually the goal. However, your specific A1C target may be different depending on your age, health conditions, and other factors. Talk to your doctor to find the A1C target and treatment plan that is right for you.4

How often should I have the hemoglobin A1C test?

How often you need the hemoglobin A1C test depends on your specific treatment plan and how well you are managing your blood sugar levels. Many doctors recommend the A1C test:1

  • 1 time per year if you have prediabetes
  • 2 times per year if you have type 2 diabetes, do not use insulin, and your blood sugar levels are usually within your target range
  • 4 times per year if you have type 2 diabetes, you use insulin, or you have trouble keeping your blood sugar levels within your target range

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