Hemoglobin A1c

What is this test?

The hemoglobin A1c test is a lab test used in the care of people who have diabetes. Hemoglobin A1c is a chemical combination of hemoglobin and glucose. Hemoglobin is the part of the red blood cells that carries oxygen. Glucose is a type of sugar in the blood that is often higher than normal in diabetics.

Why is it done?

Hemoglobin A1c is an excellent way to check how well you are controlling your blood sugar over a 3-month period.

Hemoglobin A1c measurements are important for at least two reasons. The first is that they confirm your daily home blood sugar monitoring results. The second is that there appears to be a direct relationship between the hemoglobin A1c level and the risk of diabetic complications. In other words, the higher the hemoglobin A1c percentage, the greater the risk of developing diabetic eye, kidney, or nervous system disease.

How do I prepare for this test?

No preparation is necessary. One of the advantages of this test is that you do not have to fast before you take it.

How is it done?

A small tube of blood is taken from your arm through a needle.

When and how will I get the results?

You may be told the results within a few minutes of the test. Otherwise, ask your health care provider when you can learn the results. Ask whether you should call for the results or whether your provider will call you.

What do the results mean?

Your hemoglobin A1c percentage is a way of looking at your average blood sugar level over a period of 3 months.

In most labs a value of 4% to 6% is normal. For diabetics the results are usually judged as follows:

  • Less than 6.5%: excellent blood sugar control
  • 7% or less: acceptable control
  • 7% to 8%: good control
  • 8% to 9%: fair control
  • higher than 9%: poor control.

The hemoglobin A1c percentage rises as your average blood sugar level rises. Sugar absorbed from the digestive system circulates in the bloodstream. Some of the sugar combines with the hemoglobin in red blood cells to form hemoglobin A1c. As more sugar circulates in the bloodstream, more hemoglobin gets changed into hemoglobin A1c.

Red blood cells live 90 to 120 days. Therefore, once sugar has combined with the hemoglobin in red blood cells, the hemoglobin A1c stays in the blood for 90 to 120 days. This means the amount of hemoglobin A1c in your blood reflects the average sugar concentration in your blood over a 3-month period.

What if my tests aren't normal?

If you have not yet been diagnosed with diabetes and your test is not normal, you need to talk with your health care provider about whether you have diabetes.

If you have been diagnosed as diabetic and your test is not normal, your health care provider will talk to you about how to lower your blood sugar through diet, exercise, and/or medicine. Maintaining blood sugar levels and hemoglobin A1c levels in or near normal ranges will help you avoid the complications of diabetes.

A few people have different types of hemoglobin than most other people. In these instances the test may not be as accurate. (It also may not be as accurate during pregnancy or if you are anemic.) If your blood sugars seem different on average than your hemoglobin A1c measurement, your doctor may investigate further.

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Adapted from content provided by iMcKesson, LLC
Review Date: 6/9/01