Diabetes Education

A1c Testing

The A1c test is an important diagnostic test for people with diabetes or who may be at risk for diabetes. An A1c test measures the Average Blood Glucose (ABG) in the body over the previous 90-120 days. Although monitoring your own glucose levels at home on a daily basis is crucial for people with diabetes, an A1c test complements self-monitoring by offering a more complete picture of how your treatment program is performing over the long term.

The A1c test is also known as a hemoglobin A1c test. Hemoglobin is an oxygen-carrying protein found in red blood cells. Red blood cells live for about 120 days, or the lifespan of a red blood cell, and then are replaced by new ones. Each red blood cell carries a “memory” of daily blood glucose levels throughout its lifetime. When surplus glucose is in the bloodstream, it hooks up with hemoglobin, causing higher A1c levels. These A1c levels are “remembered” by the red blood cells and can be analyzed by an A1c test. Specifically, the A1c test shows whether your ABG is above normal by measuring the percentage of glycated hemoglobin. In a non-diabetic person, about 5% of all hemoglobin is glycated (or, attached to glucose). In a person with diabetes, this percentage can jump to 25% in extreme cases.

When too much glucose is in the bloodstream, hemoglobin cannot deliver as much oxygen as is needed by the body’s cells. Without oxygen, the cells suffer damage. Numerous studies have reliably linked above-normal A1c results with complications such as nerve, eye, kidney, and cardiovascular disease.

If your diabetes treatment program is not working effectively enough, an A1c test alerts your healthcare team that further adjustments are needed. Diabetics should have an A1c test at least twice per year. In some cases, it is advisable to perform the test every 3 months, such as when you’ve begun a new medication or when your blood glucose readings are not yet under control.

Although the A1c test is an important tool for diabetes management, it is vital to emphasize that the test is not a replacement for daily monitoring of blood glucose levels. An A1c test can’t help you adjust your insulin dosages, for example. Check with your doctor to determine how the A1c test should fit into your diabetes management.

Marci Sloane, MS, RD, LD/N, CDE

Article was reviewed by Marci Sloane, a registered and licensed dietitian/nutritionist and certified diabetes educator. Marci graduated with a degree in Nutrition and Physiology from Teachers College at Columbia University. Marci manages a Diabetes and Nutrition Education Center in South Florida and is the author of The Diet Game: Playing for Life!

The goal of Destination Diabetes® is to be a useful and credible resource for the more than 20 million children and adults who have diabetes in the U.S. and their families. Destination Diabetes® provides information on a wide range of diabetes health and wellness topics. Articles are written or reviewed by diabetes advisors who have experience in diabetes education.