Someone with an A1c of 6.4 percent has an estimated average glucose between 126 and 154 milligrams per deciliter, reports the National Diabetes Information Clearinghouse. The A1c test determines a person's average glucose level over the preceding three months.
Doctors use the A1c test to diagnose prediabetes and Type 2 diabetes, states the National Diabetes Information Clearinghouse. An A1c result below 5.7 percent is considered normal. People with prediabetes have A1c levels ranging from 5.7 to 6.4 percent, while diabetics have A1c levels above 6.4 percent. An A1c of 6 percent correlates to an estimated average glucose level of 126 milligrams per deciliter. If the A1c result is 7 percent, the person has an estimated average glucose level of 154 milligrams per deciliter.