Hemoglobin A1c (HbA1c) from whole blood, measured by high-performance liquid chromatography (HPLC)

Why is this test done?

Doctors order HbA1c tests primarily to diagnose type 1 or type 2 diabetes, monitor diabetes treatment effectiveness, or detect prediabetes. It’s also useful for evaluating how well blood sugar levels have been controlled over time, especially in people with chronic conditions like diabetes.

How is the test performed?

A small blood sample is taken from your arm, usually during a routine office visit or lab visit. The blood is processed to measure the percentage of hemoglobin that is coated with sugar (HbA1c) using a specialized HPLC method.

What does the result mean?

Results are reported as a percentage. While exact reference ranges vary by lab, higher percentages generally indicate poorer blood sugar control. For example, a result below 5.7% may suggest prediabetes, while 6.5% or higher may indicate diabetes. Your doctor will interpret results in the context of your overall health and treatment plan.

What can affect this test?

Several factors can influence HbA1c results, including recent blood sugar fluctuations, pregnancy, certain medications (like insulin or oral diabetes drugs), blood loss, or iron deficiency. Smoking and certain medical conditions (e.g., kidney disease) may also impact results.