Mayo Clinic provides an A1C chart online. This chart displays A1C test results with the corresponding estimated blood sugar levels, allowing an accurate diagnosis of diabetes. A normal A1C for someone who has never had diabetes falls in the range between 4.5 and 6 percent, according to Mayo Clinic.
Because they rely on hemoglobin levels, A1C tests can be less effective for those who experience chronic or heavy bleeding, those with insufficient iron in their blood, those with uncommon variants of hemoglobin, and anyone who has recently had a blood transfusion. Results may also vary slightly from one lab to another, as Mayo Clinic points out.