Hemoglobin A1c Test

You can learn how well you are managing your diabetes by taking a special blood test on a regular basis. It's called the hemoglobin A1c test, also called HbA1c or A1C for short.  The A1C measures your average blood glucose level over the past three months.

This test can be a powerful tool in managing your diabetes. Here's how and why it works. Over the course of a day, it's normal for your blood sugar level to go up and down. The specific amount of sugar in the blood at any given time is known as your "free blood glucose level."

Before a meal, free blood glucose levels are generally low. After a meal, the free blood glucose level rises as food is digested, and then gradually returns to a lower level as insulin is released from the pancreas and the body's cells take glucose from the blood and use it for energy. When glucose is in the blood stream waiting to be used by the cells, some of it can become permanently attached to red blood cells. The attachment occurs at the same part of the red blood cell that carries oxygen, called the hemoglobin molecule, but does not affect the cell's ability to carry oxygen.

In the absence of diabetes, the body takes glucose efficiently into the cells, so there is usually very little free glucose available to attach to hemoglobin. In that case, the A1c level stays around 4 to 6 percent, which means that only 4 to 6 percent of red blood cells have glucose attached to them.

When you have diabetes, your cells can't get the glucose they need, either because your body produces little or no insulin (as in type 1 diabetes), or because it can't respond to the insulin that it does produce (as in type 2 diabetes). In either case, you end up with an excess amount of free blood glucose. More glucose in the blood means more glucose attaching to the red blood cells, and that's why the A1c level in a person with untreated diabetes may be as high as 10 percent or more.

The higher your A1c test results, the greater the amount of sugar in your blood. And high blood sugar over a long period of time may increase your risk of diabetes complications.

Because red blood cells live in the body for about 90 days, the A1c test result represents an average free blood glucose level over a three-month period of time. You can have high blood sugar on some days and low blood sugar on others, and the average could be a "good" A1c reading. That's why it's still important to check your own blood sugar daily, as well as having the test done.

The A1c test gives you and your doctor an important perspective to how well you are managing your diabetes. With careful management, it's even possible for a person with diabetes to have close to normal hemoglobin A1c levels (the American Diabetes Association guidelines call for a level of seven percent or less).

It could take several months to reach your A1c target, depending on how high your initial level is. What's important is that you move in the right direction, always toward the target level. And take the test regularly: the ADA recommends that you do so every three months.

Download A1C target worksheet

Download A1C brochure




The BD Diabetes Learning Center describes the causes of diabetes, its symptoms, and diabetes complications such as retinopathy and neuropathy. This site contains detailed information about blood glucose monitoring, insulin injection and safe sharps disposal. Interactive quizzes, educational literature downloads and animated demonstrations help to teach diabetes care skills.

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