A normal A1C value range for a non-diabetic patient is between 4.5 and 6 percent, according to Mayo Clinic. If A1C levels measure above 6.5 percent on two separate occasions, a doctor may diagnose diabetes.
A1C levels correspond to average blood sugar levels, explains Mayo Clinic. For example, a 6 percent A1C value corresponds to an average blood sugar level of 126 milligrams per deciliter, the units in which most blood glucose monitors report readings. Average blood sugar is a more accurate gauge for a diabetes diagnosis, as blood sugar levels change throughout the day and before and after meals.