Clinical and Laboratory Standards Institute document POCT05-A--Performance Metrics for Continuous Interstitial Glucose Monitoring; Approved Guideline provides a consensus for health care professionals, in vitro diagnostic (IVD) and medical device manufacturers, and regulatory agencies on how continuous glucose monitor (CGM) data should be: 1) presented; 2) compared between devices; and 3) compared between measurement technologies. Terminology is defined for measuring interstitial fluid glucose levels and comparing them to blood glucose levels. The degree of agreement for acceptable technical performance is defined to assess method comparability. This guideline also presents methods for testing CGM performance and interpreting CGM levels. This guideline covers CGM point accuracy and trend accuracy, as well as CGM measurement sensitivity and specificity. The guideline covers device instability due to changes in sensitivity over time. The guideline covers analytical and clinical metrics for establishing the calibration process. It covers approaches for accounting for lag time, which consists of physiologic lag plus process delay. Finally, for CGM measurements, the guideline covers how to use reference materials and establish traceability to a reference system.