Your CGM numbers
What Is Time in Range? CGM Targets Explained
Time in range, or TIR, is the percentage of time your glucose stays between 70 and 180 mg/dL (3.9 to 10.0 mmol/L). It is calculated from continuous glucose monitor (CGM) data, and it shows something an A1C can’t: how much of your time was spent low, in range or high.
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How time in range is calculated
A CGM records a glucose reading every few minutes. Time in range is the share of those readings that fall between 70 and 180 mg/dL. If 17 of every 24 hours land in that band, your time in range is about 70%.
The same readings are also split into time below range and time above range, which is why a CGM report usually shows several percentages that add up to 100%.
The consensus targets
The 2019 International Consensus on Time in Range, written by a group of clinicians and researchers and published in Diabetes Care, set out targets for CGM data. For most adults with type 1 or type 2 diabetes:
- Time in range (70 to 180 mg/dL): more than 70%, about 17 hours a day
- Time below 70 mg/dL: less than 4%, about 1 hour a day
- Time below 54 mg/dL: less than 1%, about 15 minutes a day
- Time above 180 mg/dL: less than 25%, about 6 hours a day
- Time above 250 mg/dL: less than 5%, about 1 hour 12 minutes a day
For older adults and people at higher risk of low glucose, the consensus uses looser targets, including more than 50% in range and less than 1% below 70 mg/dL. Targets also differ in pregnancy.
These are population targets, not a pass mark. The right target for you depends on your age, health and goals, and it is set with your care team.
How much data you need
The consensus suggests at least 14 days of CGM data, with the sensor active for at least 70% of that time, before reading much into the percentages. A few days is a snapshot. Two weeks starts to show a pattern.
What time in range doesn’t tell you
- Why. It says how much time you spent out of range, not what pushed you there: a meal, a dose, a poor night, a hot day.
- When. Two people can share the same 70% and have very different days. One may drift high every afternoon while another swings overnight.
- How low. A single in-range percentage says nothing about lows. The below-range numbers matter on their own.
How Dia shows it
Dia’s Patterns tab shows time in range as a ring, and its “Your numbers” screen uses these published definitions, so what you see matches what your clinic reports. Dia describes your data and looks for what lines up with it. It does not set targets for you.
Questions
Is 70% time in range good?
70% is the consensus target for most adults with diabetes. It is a reference point rather than a grade. What is right for you is a conversation for your care team.
How is time in range different from A1C?
A1C is a lab blood test that reflects average glucose over roughly the past two to three months. Time in range comes from CGM readings, usually the last 14 days, and shows how glucose was distributed. They answer different questions, which is also why a CGM-based estimate of A1C and a lab result can differ.
Can I work out time in range without a CGM?
Not meaningfully. It needs frequent readings across the day and night, which occasional finger-stick checks can’t provide.