Time in Range (TIR) refers to the percentage of time that glucose levels fall within specific categories—low, target, or high—over a given period. This metric is calculated based on glucose readings collected from a continuous glucose monitoring (CGM) system.

Each glucose reading is evaluated against a predefined target range and categorized as one of the following:

• In Range: Glucose is within the target range.
• High: Glucose is above the upper limit of the target range.
• Low: Glucose is below the lower limit of the target range.
• Urgent Low: Glucose is extremely low and considered dangerous.

The system counts the number of readings in each category and calculates the percentage of time spent in each range. TIR reports may also distinguish between daytime and nighttime periods to provide a more detailed view of glucose patterns.

This approach helps assess overall glucose control and supports better treatment decisions.