What is an A1C test?

Doctors order an A1C test to diagnose both type 1 and type 2 diabetes and to monitor the effectiveness of diabetic treatment plans, according to Mayo Clinic. The test measures the percentage of hemoglobin in the blood that is glycated, or coated with sugar.

Higher levels of A1C indicate poor control of blood sugar, heightening the risk of complications caused by diabetes, advises Mayo Clinic. Because the A1C test measures average blood sugar levels over a period of two to three months, this test more accurately reflects the effectiveness of an overall treatment plan than tests that only check blood sugar at specific points in time.