The A1c test is a common blood test used to diagnose diabetes. An A1c of 5.7 to 6.4% is considered prediabetes, and changes to lifestyle and diet can help prevent prediabetes from developing into the disease. Researchers suggest free A1c tests at all check-ups and at drugstores with an advertising campaign would help identify more people with prediabetes, and help them prevent their condition from progressing. Read more