A glycosylated hemoglobin A1C (called HbA1c, Hemoglobin A1C, A1 and A1C) blood test reading reveals your average blood glucose level over the past three months and can be used to predict your risk for diabetes complications. This blood glucose test is used most frequently to assess glucose control in insulin-dependent diabetics whose glucose levels are very labile and in whom single blood glucose measurements may not accurately reflect the level of control present over the preceding weeks.