MARD Accuracy Metrics
Mean Absolute Relative Difference (MARD) is the gold-standard metric for CGM accuracy, with <10% being the threshold for non-adjunctive use.
Reviewed by CGM AFIA Editorial Team. Last reviewed: 2026-01-24.
Author: CGM AFIA Editorial Team
Part of: Accuracy and Interstitial Lag Time
What is MARD?
Mean Absolute Relative Difference (MARD) is the gold-standard metric for CGM accuracy. It's calculated as the average percentage difference between sensor readings and a reference [blood glucose](/glossary/#term-blood-glucose) value.
Industry Standards
A MARD of <10% is the industry threshold for non-adjunctive use—meaning dosing insulin without fingerstick confirmation.
Leading Device Performance
Limitations of MARD
MARD has important limitations:
The Averaging Problem
MARD is an average that can obscure poor performance in specific ranges, particularly hypoglycemia.
The Denominator Effect
At low glucose values, the percentage errors become inflated. A 10 mg/dL difference at 70 mg/dL is a 14% error, while the same absolute difference at 200 mg/dL is only 5%.
Comprehensive Evaluation
Clinical evaluation also relies on:
- Consensus Error Grid Analysis: Zone A/B placement indicates clinical accuracy
- iCGM regulatory standards: FDA requirements for automated insulin delivery compatibility