A1c Related to Average Glucose Levels

Diabetics test drops of their blood to monitor their bodies' use of sugars. Diabetics' doctors track longer term averages that have been reported in different units. This information has therefore been difficult for patients to understand and use to guide their daily behavior.

Self-Monitoring

• Diabetics monitor their condition in milligrams of glucose per deciliter of blood, abbreviated mg/dl. These values may vary by 40 units or more in the course of the day, depending on diet and exercise, medications and timing.

A1c

• A1c, or hemoglobin A1c, is a lab test that measures the percentage of red blood cells that are "glycosylated," the type that glucose binds to. This indicates how well the patient's blood glucose has been controlled over the preceding two or three months. Unfortunately, many patients have no way to compare A1c levels above or below the diagnostic boundary of 6.5 to the daily meter readings they receive.

Estimated Average Glucose

• To make the results of A1c tests more useful to patients, researchers in 2008 correlated the self-monitored blood glucose of 507 patients over three months with their A1c tests at the end of the study period. They developed a formula to translate A1c percentages into mg/dl estimates, abbreviated eAG. The American Diabetes Association now provides a simple calculator that uses this formula on their website.