What to know first
- Below 5.7% is normal, 5.7–6.4% is the prediabetes range, and 6.5% or above is the diabetes range.
- Diagnosis usually requires confirmation unless clear symptoms are present.
- Certain health conditions can make A1C less reliable.
Read the range correctly
NIDDK lists an A1C below 5.7 percent as normal, 5.7 to 6.4 percent as prediabetes, and 6.5 percent or above as diabetes. The higher the result within the prediabetes range, the higher the risk of developing type 2 diabetes.
A laboratory result should be interpreted with symptoms, risk factors, and other tests. Point-of-care A1C tests should not be used by themselves to diagnose diabetes.
Know the limitations
Conditions that change red blood cell turnover, certain hemoglobin variants, pregnancy, kidney disease, liver disease, blood loss, or transfusion can affect accuracy. A clinician may use fasting plasma glucose or an oral glucose tolerance test instead.
Do not change diabetes medication from a single reading without medical guidance. If a result surprises you, ask how it was measured and whether confirmation is needed.
Sources and further reading
This article is independently written from the linked public guidance. Open each source to review the original wording, context, and latest update.