Which CGM metric is best used to assess time within target range, and what is a typical target?

• A. Mean glucose with goal <100 mg/dL
• B. Time above range (TAR) with goal >50%
• C. GMI with goal <5.5
• D. Time in range (TIR: 70-180 mg/dL) with goal >70%

Answer: (D)

Time in Range is the CGM metric that directly measures how much of the day glucose stays within the target window, typically 70–180 mg/dL. This gives the clearest picture of glycemic control because it accounts for both how often readings are in range and how long they stay there, rather than just averaging all values. A common goal is to have more than 70% of readings in range, meaning roughly 16.8 hours a day within 70–180 mg/dL. Other metrics like mean glucose or GMI summarize central tendency and can miss fluctuations, and time above range describes excursions above target but doesn’t convey time spent in range as directly.