CGM MARD Comparison
We aggregate clinical trial data to compare the accuracy of continuous glucose monitors. Numbers reflect the overall MARD reported in pivotal FDA trials.
| Device | Overall MARD | Wear Time | Calibration |
|---|---|---|---|
| FreeStyle Libre 3 | 7.9% | 14 Days | Factory |
| Dexcom G7 | 8.2% | 10 Days | Factory / Optional |
| Eversense E3 | 8.5% | 180 Days | 1-2 per day |
| Dexcom G6 | 9.0% | 10 Days | Factory / Optional |
| FreeStyle Libre 2 | 9.2% | 14 Days | Factory |
| Medtronic Guardian 4 | 10.6% | 7 Days | Factory |
Understanding the Data
MARD is calculated by comparing CGM readings to a lab-quality reference (usually YSI) during clinical trials. A lower number indicates the sensor readings align more closely with actual blood glucose levels.
While a sub-8% MARD is excellent, clinical MARD does not always translate directly to personal experience. Sensor placement, body chemistry, hydration, and rapidly changing glucose levels all impact real-world performance.
The "Day 1" Problem
Almost all sensors exhibit higher MARD (lower accuracy) during the first 12-24 hours of wear due to local tissue trauma from insertion. For example, Dexcom G7 reports a Day 1 MARD of 9.3%, which improves on subsequent days.