Health Risk

A1C Calculator

Convert between A1C and estimated average glucose (eAG), and see which diabetes category your A1C falls into. Based on the ADAG study formula used by the ADA.

What is A1C and why does it matter?

Hemoglobin A1C (also called glycated hemoglobin or HbA1c) reflects your average blood glucose over the past 2-3 months. Unlike a fasting glucose test, which captures a single moment, A1C captures the long-term picture because glucose attaches slowly to hemoglobin inside red blood cells, and red blood cells live for roughly 120 days. This makes A1C the gold-standard metric used by the American Diabetes Association for both diagnosing diabetes and monitoring how well it is being managed.

The official ADA cutoffs

A1C below 5.7% is considered normal. Between 5.7% and 6.4% is classified as prediabetes, a state where blood sugar is elevated but not yet in the diabetic range. An A1C of 6.5% or higher, confirmed on a separate day, meets the diagnostic threshold for type 2 diabetes. For most adults already living with diabetes, the ADA recommends a treatment target of less than 7.0%, though individualized targets between 6.5% and 8.0% may be appropriate based on age, comorbidities, and hypoglycemia risk.

How the eAG conversion works

The estimated Average Glucose (eAG) formula, eAG (mg/dL) = 28.7 × A1C − 46.7, comes from the landmark ADAG (A1C-Derived Average Glucose) study published in 2008, which compared A1C to continuous glucose monitoring in 507 people across 10 international centers. The conversion lets you translate an abstract percentage into the same mg/dL units you see on a glucose meter, which makes it easier to understand what an A1C result really means day to day.

What can move A1C up or down (beyond glucose)

Anything that changes red blood cell lifespan can skew A1C. Iron deficiency anemia, kidney disease, recent blood loss or transfusion, sickle cell trait, and pregnancy can all produce misleading results. In these situations, your clinician may order alternatives like glycated albumin, fructosamine, or continuous glucose monitoring. Always interpret your result in conversation with a healthcare provider who knows your full medical context.

Editorial and formula review

Researched by Macrition Research Team Formulas verified against published peer-reviewed sources Last verified 2026-08

Formula sources, population limits, and references for this health risk calculator are documented in our public methodology. Read the methodology · Medical disclaimer

Frequently asked questions

For people without diabetes, every 3 years starting at age 35, or earlier and more often if you have risk factors. For diagnosed diabetes, the ADA recommends every 3 months if therapy changed or targets are not met, and every 6 months once stable.

Yes, especially in prediabetes. A 5-7% body weight loss, 150 minutes of weekly moderate exercise, and a higher-fiber lower-processed-carb eating pattern can lower A1C by 0.5-1.0 percentage point or more over 3-6 months.

No. Fasting glucose measures one moment; A1C averages roughly the past 90 days. They can disagree, a person with normal fasting glucose but high post-meal spikes can still have an elevated A1C.

For most non-pregnant adults with diabetes, the ADA target is below 7.0%. Older adults or those with cardiovascular disease may target 7.5-8.0% to avoid hypoglycemia. Prediabetes should target below 5.7%.

No. Because A1C reflects the past 2-3 months, you can take the test at any time of day without fasting or other preparation.