The A1C test is a blood test used to diagnose Type 1 and Type 2 diabetes. It also gauges how well diabetes is being managed through a diabetes treatment plan, according to Mayo Clinic. The A1C test provides an average of blood sugar levels for two or three months.
The A1C test measures the percent of hemoglobin coated with sugar. Hemoglobin is the protein in red blood cells responsible for carrying oxygen. When an A1C level is high, the risk of complications with diabetes increases, explains Mayo Clinic. A higher A1C level also indicates poor blood sugar control. Blood is taken from the vein or a tip of a finger for the test.