Unmasking Hidden Dysglycemia: A Mobile OGTT Approach Using Continuous Glucose Monitors

Prediabetes (PD), which includes impaired glucose tolerance (IGT) and impaired fasting glucose (IFG), is a dysfunctional metabolic state that often progresses to type 2 diabetes (T2D). Standard screening tools such as random glucose and hemoglobin A1c frequently miss early or intermittent dysglycemia and cannot distinguish underlying physiological differences relevant for targeted intervention. Although the oral glucose tolerance test (OGTT) detects more PD and T2D and identifies high-risk individuals earlier, its clinical use is limited by the need for repeated venous sampling and in-clinic administration. We introduce the mobile OGTT (mOGTT), which leverages continuous glucose monitoring (CGM) to capture high-resolution glycemic responses to a standardized glucose challenge outside clinical settings. In a population spanning a broad range of glycemic health, we establish preliminary normative mOGTT values, characterize their relationship to clinical OGTT thresholds, and assess concordance with A1c. We show that CGM-derived analogs of OGTT metrics improve detection and phenotyping of dysglycemia and propose the Glucose Challenge Response Index (GCRI), a composite measure of glycemic health. Finally, we demonstrate the generalizability of GCRI-based subphenotypes in an out-of-sample cohort. These results help facilitate an efficient and scalable approach for conveniently detecting and quantifying early-stage glucose dysregulation.