The A1C test is a blood test that reveals the average of an individual's blood sugar levels over the three months before testing, states the National Diabetes Information Clearinghouse. The test is based on glucose-hemoglobin attachment, reported as a percentage. An A1C level below about 5.7 percent is considered normal.
Hemoglobin is the oxygen-carrying protein in red blood cells, which usually live for approximately three months, the A1C test measurement period, notes the National Diabetes Information Clearinghouse. A test result of about 5.7 to 6.4 percent indicates a risk of developing diabetes, and a test result of about 6.5 percent and above indicates diabetes. A patient undergoing A1C testing does not have to fast, and can give the blood sample at any time of day. The A1C test, also known as the glycohemoglobin test, is among the significant tools for researching, diagnosing and managing diabetes, as of 2015.