Free tool
GMI calculator
Glucose Management Indicator from your average CGM glucose. Runs in your browser; nothing is sent anywhere.
What GMI is
GMI is the A1c you would expect from your average CGM glucose. The formula was fitted by Bergenstal and colleagues in 2018 from paired CGM and lab A1c data, and it replaced the older "estimated A1c" label because the two numbers are not the same thing: A1c is a lab measure of red blood cells over about three months, and GMI is a calculation from sensor readings over the period you pick. In that dataset, 28% of people had a GMI and a lab A1c that differed by 0.5 points or more.
The formula
- GMI (%) = 3.31 + 0.02392 × average glucose in mg/dL
- GMI (mmol/mol) = 12.71 + 4.70587 × average glucose in mmol/L
The international consensus on CGM metrics (Battelino et al., 2019) recommends at least 14 days of data with the sensor worn 70% of the time before reading a GMI as a summary.
Quick table
| Average mg/dL | Average mmol/L | GMI |
|---|---|---|
| 100 | 5.6 | 5.7% |
| 126 | 7.0 | 6.3% |
| 140 | 7.8 | 6.7% |
| 154 | 8.5 | 7.0% |
| 183 | 10.2 | 7.7% |
| 212 | 11.8 | 8.4% |
| 240 | 13.3 | 9.1% |
Glide's Insights tab shows the same GMI for the last 14 days beside time in range and GRI, computed with this formula from the readings it stores in mg/dL.