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What is a Hemoglobin A1C Test?

The results can give you a picture of how well your blood sugar is controlled.

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Whether or not you take insulin every day, it’s important to check your progress to see how well your diabetes is controlled. That's where knowing your A1C can help. The A1C test shows what your average blood glucose level has been over the past two to three months. It’s a simple blood test that rounds out the daily ups and downs to show you and your doctor how well your diabetes treatment plan has been working.

What is hemoglobin A1C and why is it important?

Hemoglobin is a protein in your red blood cells. It binds (or glycates) to sugars and carries oxygen from the lungs to the cells. When your blood sugar is high, more hemoglobin attaches to the sugars. The A1C test measures the hemoglobin that has attached to the sugars. Red blood cells stay in the bloodstream for about four months. Measuring the glycated hemoglobin shows what's been happening over this time period. 

A higher A1C reading means your blood sugar levels have been high. A lower A1C reading indicates your blood sugar levels are likely under control.

What is a good A1C reading?

Hemoglobin A1C is measured in percentages. Your doctor may set your personalized goal between 6 and 8, based on factors such as age, health, risk of hypoglycemia and your personal situation.

It’s recommended that you have your doctor test your A1C. This way, he or she can discuss the results with you and adjust your medication if necessary.

How often do I need this test?

If your diabetes is controlled and you’re at your target A1C level, your A1C should be tested at least twice a year. If you’re not at your target A1C level, your doctor may want to test your A1C every three months.

If you’re taking insulin, the A1C test should be done in addition to regular home blood glucose monitoring. It may be helpful to think about blood glucose testing like checking your watch and A1C like looking at your calendar.

By Jenilee Matz, MPH, Contributing Writer

American Diabetes Association. Standards of medical care in diabetes—2015. Diabetes Care. 2014;1:S14-S80. Accessed: April 13, 2015.
National Diabetes Information Clearinghouse. The A1C test and diabetes. Accessed: March 25, 2015.
American Diabetes Association. Blood glucose testing. A1C. Accessed: March 25, 2015.
Copeland, KC, et al. Clinical practice guideline management of newly diagnosed type 2 diabetes mellitus (T2DM) in children and adolescents. American Academy of Pediatrics. 2013;131, No. 2: 364-382 . Accessed: March 25, 2015.

Last Updated: April 23, 2015