Mean absolute relative difference

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Mean Absolute Relative Difference (MARD) is a common way to judge how accurate a continuous glucose monitor (CGM) is. It tells you, on average, how far a CGM reading is from the real blood glucose, shown as a percentage. To calculate MARD, you compare many CGM readings with reference values from a lab or a precise glucose meter, take the absolute percentage error for each pair, and then average those errors. A smaller MARD means the CGM is more accurate. Researchers and regulators use MARD to compare different CGM devices. Keep in mind that MARD can vary from person to person even with the same device.