How A1C converts to average blood sugar
The formula comes from the A1C-Derived Average Glucose (ADAG) study, which compared A1C with continuous glucose readings in hundreds of people. The American Diabetes Association uses it to report estimated average glucose (eAG).
Example: an A1C of 6.5% means an average blood sugar of about 28.7 × 6.5 − 46.7 = 140 mg/dL, or 7.8 mmol/L. Going the other way, an average of 154 mg/dL works out to an A1C of about 7.0%.
A1C ranges
| A1C | eAG | Range used for diagnosis |
|---|---|---|
| Below 5.7% | Below 117 mg/dL | Normal |
| 5.7% to 6.4% | 117 to 137 mg/dL | Prediabetes |
| 6.5% or above | 140 mg/dL or above | Diabetes |
| 7.0% | 154 mg/dL | A common treatment goal for many adults with diabetes |
| 8.0% | 183 mg/dL | |
| 9.0% | 212 mg/dL |
A1C reflects the past two to three months, weighted toward the most recent weeks. It can read falsely high or low with anemia, recent blood loss or transfusion, pregnancy, kidney disease and some hemoglobin variants, so a diagnosis is usually confirmed with a second test. This calculator is for understanding results; your doctor sets your goals and treatment.
Frequently asked questions
What is a normal A1C?
Below 5.7%. A result from 5.7% to 6.4% is in the prediabetes range, and 6.5% or higher is in the diabetes range.
What average blood sugar is an A1C of 7?
About 154 mg/dL, or 8.6 mmol/L, using the ADAG formula.
Why doesn't my meter average match my A1C?
Finger-stick averages only include the moments you test, often before meals, and miss highs after eating and lows overnight. Red blood cell lifespan also varies between people, which shifts A1C slightly.
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