Clinical Implications and Applicability of Time in Tight Range

Alongside time in range (TIR, 70–180 mg/dL), an established continuous glucose monitoring (CGM) metric, time in tight range (TITR, 70–140 mg/dL) was originally proposed to reflect glucose exposure closer to physiological normoglycemia, although its clinical applicability has often been considered limited to intensive glycemic control settings. Physiological CGM data show that individuals with normoglycemia spend most of their time below 140 mg/dL, and longitudinal studies in high-risk populations demonstrate that time above 140 mg/dL predicts progression to diabetes. While concerns have been raised that increases in TITR may coincide with higher glycemic variability, particularly in hyperglycemic states, this interpretation is context dependent. In recent analyses, at an HbA1c level of approximately 7.0%, TIR varied widely according to glycemic variability, whereas TITR converged within a relatively narrow range (about 47~48%), indicating a variability-independent reference zone. Moreover, TITR outperformed TIR in predicting attainment of the HbA1c 7.0% target. TITR is already widely recognized as a superior metric in settings of tight glycemic control. Beyond this established role, emerging evidence suggests that TITR also provides complementary and clinically meaningful information across common glycemic targets and hyperglycemic states, thereby enhancing interpretation of glucose distribution beyond conventional CGM metrics.