The A1C blood test for diabetes helps gauge how well the patient is managing his disease. The test results indicate the average blood sugar levels for the past 60 to 90 days by measuring the percentage of the hemoglobin bound to glucose, according to Mayo Clinic.
Hemoglobin is a protein in the blood responsible for carrying oxygen. When blood glucose levels are high, the sugar in the blood combines with hemoglobin. In patients without diabetes, the normal A1C reading is between 4 and 5.6 percent, according to WebMD. Test results between 5.7 and 6.4 percent indicate the patient is at risk for developing diabetes. A person with an A1C of 6.5 percent or higher is a diabetic. For diabetics, the goal is keeping the A1C levels below 7 percent in order to reduce the chances of developing diabetic complications.
As of 2015, A1C tests are more accurate due to the work of the National Glycohemoglobin Standardization Program, and the test results provide the required accuracy for diagnosing Type 2 diabetes and prediabetes, according to the National Diabetes Information Clearinghouse. While the standard glucose test requires the patient to fast for several hours before drawing the blood, the A1C test does not. Eliminating the need for fasting improves the chances of patients having the test, which could reduce the number of undiagnosed diabetics.