With the widespread adoption of CGM (continuous glucose monitoring), glycemic control can now be evaluated across a continuous time axis rather than at isolated time points. This shift has led to the emergence of time-based glycemic metrics, which quantify the proportion of time glucose levels remain within predefined ranges and provide a more comprehensive assessment of glycemic exposure. Among these metrics, time in range (TIR; 70–180 mg/dL) has become the standard indicator for overall glycemic control, as it integrates both hypoglycemic and hyperglycemic exposure and shows robust associations with microvascular complications independent of HbA1c. However, TIR alone may be insufficient to discriminate qualitative differences in glycemic control among individuals who have already achieved stable or near-target glucose levels. In this context, time in tight range (TITR; 70–140 mg/dL), reflecting glucose levels closer to normal physiology, has been proposed as a complementary metric. This article discusses the conceptual framework and clinical implications of time-based glycemic metrics, with a particular focus on the distinct and complementary roles of TIR and TITR.
Jinyoung Kim (Mon,) studied this question.