An international committee of experts from the American Diabetes Association, the European Association for the Study of Diabetes and the International Diabetes Federation recommends that the A1C test be the primary test used to diagnose prediabetes, type 1 diabetes and type 2 diabetes.

After a diabetes diagnosis, the A1C test is used to monitor your diabetes treatment plan. Since the A1C test measures your average blood sugar level for the past two to three months instead of your blood sugar level at a point in time, it is a better reflection of how well your diabetes treatment plan is working overall.

Your doctor will likely use the A1C test when you're first diagnosed with diabetes. This also helps establish a baseline A1C level. The test may then need to be repeated while you're learning to control your blood sugar.

Later, how often you need the A1C test depends on the type of diabetes you have, your treatment plan and how well you're managing your blood sugar. For example, the A1C test may be recommended:

  • Twice a year if you have type 2 diabetes, you don't use insulin, and your blood sugar level is consistently within your target range
  • Three to four times a year if you have type 1 diabetes
  • Four times a year if you have type 2 diabetes, you use insulin to manage your diabetes, or you have trouble keeping your blood sugar level within your target range

You may need more frequent A1C tests if your doctor changes your diabetes treatment plan or you begin taking a new diabetes medication.

Jan. 30, 2013