A hemoglobin A1c blood test indicates your average blood sugar level over the past three months. It is the standard indicator whether someone is a diabetic, of how well-controlled a current diabetic's regimen has been, and of how at-risk someone is for developing diabetic complications. The American Diabetes Association recommends an A1c of below 7.0 percent.

Diabetes

Having diabetes, which means your body does not produce enough (or any) insulin to regulate the amount of glucose in your bloodstream, will cause A1c results to fluctuate more widely than not having diabetes. A person with an A1c result of 6.5 percent or higher will be diagnosed as diabetic.

Blood Glucose

The primary factor affecting A1c results is how much excess glucose (sugar) is in the bloodstream. If there is too much glucose in the blood (high blood sugar), some of the extra glucose bonds to hemoglobin, which is found in red blood cells. The more excess glucose, the more of it bonds to hemoglobin. This bond is permanent and lasts until the red blood cell dies, which typically takes three months.

Blood Glucose Control

The tighter your blood sugar levels are controlled, the lower the A1c level, and vice versa.

Time Frame

Because the lifespan of a red blood cell can vary, the amount of excess glucose in the blood over the past 30 days has a greater impact on A1c test results than earlier excesses.

Expert Insight

While the A1c test is primarily used to diagnose and monitor diabetes, other conditions can affect A1c results, including renal (kidney) failure, hemoglobinopathy, and red blood cell disorders.

Source:

American Diabetes Association Journal: A1C: Does One Size Fit All?

Diabetes Health: What Is A1C and What Does It Measure?