Lack of Association Between Hemoglobin A1c and Continuous Glucose Monitor Metrics Among Individuals with Prediabetes and Normoglycemia

Continuous glucose monitors (CGMs) are becoming increasingly available, yet the relationship between CGM metrics and hemoglobin A1c (HbA1c) among individuals with prediabetes and normoglycemia remains unclear. We examined associations between HbA1c and eight CGM metrics across glycemic status. Our cohort included 972 individuals: 421 (43.3%) with type 2 diabetes, 319 (32.8%) with prediabetes, and 232 (23.9%) with normoglycemia. Associations were strongest in type 2 diabetes, with mean glucose showing the strongest relationships (standardized β = 0.79, P < 0.001). In prediabetes, associations were substantially attenuated, with mean glucose showing moderate association (standardized β = 0.22, P < 0.001). Among individuals with normoglycemia, CGM metrics showed minimal associations with HbA1c, with mean glucose demonstrating a weak association (standardized β = 0.10, P = 0.022) and time in range showing no significant relationship. All interaction terms were statistically significant ( P < 0.001). These findings suggest that standard CGM metrics should not be interpreted to reflect HbA1c for individuals with prediabetes and normoglycemia.