What is Time in Range (TIR)? A Plain-English Guide

Your CGM report has one number that matters more than almost any other — Time in Range. Here's what it actually means, in plain English.

Time in Range, defined

Time in Range (TIR) is the percentage of time your glucose stays inside your target window. The standard target for most adults is 70–180 mg/dL (3.9–10.0 mmol/L).

If your CGM says "Time in Range 68%," it means you spent roughly two-thirds of the last 7, 14, or 90 days inside that window — and the rest outside it.

Why TIR matters more than a single reading

A single glucose value is a snapshot. TIR is the movie. It captures how much of your day you spend in a healthy range, which is a far better predictor of long-term outcomes than any one moment's number.

It also maps closely to your HbA1c: roughly speaking, every 10% change in TIR corresponds to about a 0.5% change in HbA1c. That's why clinics now look at TIR alongside (and sometimes instead of) A1c.

What's a good target?

The international consensus (from the ATTD expert group) is:

• Time in Range (70–180 mg/dL): more than 70%
• Time Below Range (<70 mg/dL / 3.9 mmol/L): less than 4% (and <1% below 54 mg/dL / 3.0 mmol/L)
• Time Above Range (>180 mg/dL / 10 mmol/L): less than 25%

Each 5% of TIR ≈ 30 minutes per day. So going from 60% to 70% TIR means about an hour more in range every single day.

Don't chase 100%

More TIR is generally better — but only if it doesn't come with more lows. A flat 100% in range that required constant hypos isn't a win. The real goal is more time in range AND fewer lows.