What is A1C?
A1C, also called HbA1c, is a blood test that reflects average blood sugar over the past two to three months. It measures how much glucose is attached to hemoglobin in red blood cells. Clinicians use it to screen, diagnose and monitor diabetes control.
How A1C is calculated
The calculator uses the standard estimated average glucose equation: eAG in mg/dL equals 28.7 times A1C minus 46.7. For mmol/L, the mg/dL value is divided by 18. Reverse conversion estimates A1C from average glucose.
A1C vs blood glucose
Daily glucose readings show short-term changes. A1C shows a longer-term average. Both are useful, but they answer different questions. A single glucose value can change after meals, exercise or stress. A1C reflects a broader trend.
A1C range chart
| A1C range | Meaning | Typical interpretation |
|---|---|---|
| Below 5.7% | Normal | Generally lower diabetes risk |
| 5.7%–6.4% | Prediabetes | Higher risk; lifestyle review is common |
| 6.5% or higher | Diabetes range | Requires clinical evaluation |
Who should use this tool?
- People tracking A1C after a lab result.
- People comparing average glucose with HbA1c.
- Fitness users monitoring metabolic trends.
- Healthcare professionals explaining eAG to patients.
Accuracy and limitations
This tool is only an estimate. Conditions such as anemia, pregnancy, kidney disease, recent blood loss or hemoglobin variants may affect A1C accuracy. Use lab results and medical advice for diagnosis or treatment.
