Understanding Hemoglobin A1c

Introduction to Hemoglobin A1c

Hemoglobin A1c is a blood test that measures the average blood sugar level over the past 2-3 months by measuring how much sugar has attached to the hemoglobin protein inside red blood cells, according to the American Diabetes Association 1

The A1c result is reported as a percentage, with higher percentages indicating higher average blood sugar levels, as stated by the American Diabetes Association 2
An A1c level of below 5.7% is considered normal, 5.7% to 6.4% indicates prediabetes, and 6.5% or higher indicates diabetes, according to the American Diabetes Association 3, 1
The target A1c level for most people with diabetes is below 7%, as recommended by the American Diabetes Association 4, 3

An A1c percentage can be translated into an average blood sugar number, with each 1% change in A1c equaling approximately a 29 mg/dL change in average blood sugar, as reported by the American Diabetes Association 4, 2
For example, an A1c of 6% corresponds to an average blood sugar of 126 mg/dL, an A1c of 7% corresponds to an average blood sugar of 154 mg/dL, and so on, according to the American Diabetes Association 4

The A1c test predicts the risk of diabetes complications, such as eye disease, kidney disease, nerve damage, and heart disease, with higher A1c levels indicating higher risk, as stated by the American Diabetes Association 4, 5
The A1c test shows how well diabetes treatment is working over time, not just on one particular day, according to the American Diabetes Association 4, 1

A1c results may not be accurate in certain situations, such as anemia, blood loss, or certain blood disorders, and daily blood sugar readings should be relied upon instead, as recommended by the American Diabetes Association 4

The A1c test should be performed every 3 months if treatment has changed or goals are not being met, and every 6 months if diabetes is well-controlled and stable, as recommended by the American Diabetes Association 4, 5