A1c is a test that shows the average level of blood sugar over the past 2 to 3 months. People who have diabetes need to have this test done regularly to see whether their blood sugar levels have been staying within a target range. This test is also used to diagnose diabetes. A1c test results show your average blood sugar level over time. The result is reported as a percentage. Your goal is to keep your hemoglobin A1c level as close to your target level as possible. You and your doctor will work together to set your safe target level.