A Comprehensive Review of the Evolving Landscape of Continuous Glucose Monitoring Metrics (Preprint)

BACKGROUND Continuous glucose monitoring (CGM) has transformed diabetes management and research by providing high-frequency data that overcomes the limitations of HbA1c, enabling more precise clinical treatment targets and responsive trial endpoints. The richness and complexity of high-resolution time-series CGM data have spurred the development of numerous metrics for both clinical care and research applications. However, this proliferation has created significant challenges in metric selection, interpretation and standardization. OBJECTIVE The objective of this systematic review is to map the current landscape of CGM metrics and address ongoing challenges in metric selection, clinical and research interpretation, and standardization. METHODS We systematically searched PubMed and Google Scholar for literature published between 2001 and 2025 on the calculation, application, and interpretation of standard and emerging CGM metrics. We extracted data on metric definitions, calculation methods, and clinical and research utility. RESULTS The review identifies a fundamental divide in the metric landscape. Standardized and clinical metrics prioritize simplicity and actionability, facilitating rapid decision-making in clinical settings but potentially masking granular glycemic fluctuations. Emerging and composite metrics offer deeper insights into glycemic patterns but lack standardization in calculation and interpretation, limiting their adoption and hindering cross-study comparison. CONCLUSIONS While consensus exists for core clinical metrics, the lack of standardization for complex metrics hinders research replicability and clinical translation. Bridging this gap requires moving toward consensus metric definitions, open-science frameworks and standardized code libraries. This review provides a comprehensive resource for navigating the diverse spectrum of CGM metrics, clarifying their applications and limitations to support both research and clinical investigation.