Diabetes and Prediabetes Diagnostic Criteria
Applies the American Diabetes Association diagnostic thresholds.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- A1C, percent
- 7.2
- Fasting plasma glucose, mg/dL
- 140
Result: Diabetes
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Diabetes
- A1C 6.5 percent or more; fasting glucose 126 mg/dL or more; 2-hour glucose 200 or more on a 75 g tolerance test; or a random glucose 200 or more WITH classic symptoms.
- Prediabetes
- A1C 5.7 to 6.4 percent; fasting glucose 100 to 125; 2-hour glucose 140 to 199.
- Confirmation
- Without unequivocal hyperglycemia, TWO abnormal results are required - two different tests at the same time, or the same test at two time points. One raised value is not a diagnosis.
- The random route
- Counts only alongside classic symptoms or a hyperglycemic crisis. Without them it is not a diagnostic route; with them it is unequivocal and needs no confirmation.
- When A1C fails
- Altered red cell turnover - anemia, iron status, splenectomy, blood loss, transfusion, hemolysis, G6PD deficiency, erythropoietin - plus HIV, cirrhosis, renal failure, dialysis and pregnancy.
- Hemoglobin variants
- An assay interference. Where any of these applies, use a glucose-based test rather than the A1C.
- Tolerance test prep
- A mixed eating pattern with at least 150 g of carbohydrate daily for 3 days beforehand. Antecedent carbohydrate restriction distorts the result and is rarely asked about.
What you enter
- A1C, percent
- Condition that alters the A1C
- Fasting plasma glucose, mg/dL
- 2-hour plasma glucose, mg/dL
- Carbohydrate restricted before the tolerance test
- Random plasma glucose, mg/dL
- Classic symptoms or hyperglycemic crisis
- Confirmed by repeating the same test
How this is calculated
American Diabetes Association Professional Practice Committee. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes-2025. Diabetes Care. 2025;48(Supplement_1):S27-S49. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.