The dawn phenomenon (DP), defined as an early-morning rise in glucose unrelated to preceding nocturnal hypoglycemia, represents a significant yet often underrecognized contributor to fasting hyperglycemia and overall glycemic instability in individuals with diabetes. The expansion of continuous glucose monitoring (CGM) technologies over the past decade has enabled more precise characterization of nocturnal glucose patterns, offering new insights into the prevalence, magnitude, and clinical implications of DP across diverse glycemic states. This review synthesizes original observational, retrospective, and prospective studies published between 2010 and 2025 that used CGM to evaluate DP in type 1 diabetes, type 2 diabetes, impaired glucose tolerance, and non-diabetic populations. Data extraction focused on DP definitions, nocturnal glucose trajectories, glycemic variability metrics, associations with HbA1c and time-in-range, and emerging evidence linking severe DP to adverse clinical outcomes. Findings indicate that DP is highly prevalent in both type 1 and type 2 diabetes, with magnitude varying widely depending on residual β-cell function, insulin sensitivity, and methodological differences in CGM-based definitions. DP correlates with increased total glucose exposure and greater glycemic variability, and may influence long-term metabolic risk. Understanding DP within the context of CGM-derived metrics is essential for optimizing individualized therapeutic strategies and improving morning glycemic control. Further standardized research is required to unify definitions and clarify the prognostic significance of DP.
Swojnóg et al. (Fri,) studied this question.