The GMI to A1C Calculator is a health and diabetes management tool that helps estimate a person’s A1C value based on their Glucose Management Indicator (GMI) or average glucose readings. This calculator falls under the medical and clinical data interpretation category. It is especially useful for individuals using Continuous Glucose Monitoring (CGM) systems who want to compare their GMI with traditional A1C laboratory results.
A1C is a common blood test that measures the average blood glucose level over the past two to three months. GMI, on the other hand, is derived from CGM data and offers a more recent and dynamic picture of glucose control. By converting GMI into an estimated A1C, patients and healthcare providers can better understand trends and adjust treatment plans accordingly.
formula
GMI Calculation
GMI (%) = 3.31 + (0.02392 × Average Glucose in mg/dL)
Where:
Average Glucose in mg/dL = The mean glucose level recorded, usually from CGM data over at least 14 days
The result is expressed as a percentage, similar to an A1C value, so it can be compared with lab-measured results.
Quick Reference Table for GMI and Estimated A1C
| Average Glucose (mg/dL) | Estimated GMI / A1C (%) |
|---|---|
| 100 | 5.7 |
| 110 | 6.0 |
| 120 | 6.2 |
| 130 | 6.4 |
| 140 | 6.6 |
| 150 | 6.9 |
| 160 | 7.1 |
| 170 | 7.3 |
| 180 | 7.6 |
| 190 | 7.8 |
| 200 | 8.0 |
This table provides quick estimates without the need for manual calculation.
Example
A person’s CGM data shows an average glucose of 150 mg/dL over the last two weeks. Using the formula:
Step 1: Multiply
0.02392 × 150 = 3.588
Step 2: Add constant
3.31 + 3.588 = 6.898
Step 3: Round result
Estimated GMI / A1C = 6.9%
This means the person’s glucose control over the measured period is similar to what a lab A1C result of 6.9% would indicate.
Most Common FAQs
No, GMI is an estimate based on CGM data, while A1C is a lab test measuring long-term glucose control. However, they can be compared to assess how closely CGM readings match lab results.
Differences can occur due to variations in red blood cell lifespan, changes in glucose control over time, or measurement method differences between CGM devices and lab tests.
No, this tool is for educational and tracking purposes only. Diagnosis and treatment decisions should be made using official lab tests and medical guidance.