Short answer: time in range (TIR) is the share of your continuous glucose monitor readings that fall between 70 and 180 mg/dL (3.9 to 10.0 mmol/L). For most adults with type 1 or type 2 diabetes, the international consensus target is more than 70% of the day, which is about 17 hours, with less than 4% of the time below 70 mg/dL and less than 1% below 54 mg/dL.
What time in range measures
A continuous glucose monitor takes a reading every few minutes, so a day produces hundreds of them. Time in range sorts those readings into three groups: in range, below range and above range. It then tells you what share of the time you spent in each.
Because a day has 1,440 minutes, every 1% of time in range is about 14 minutes. Moving from 60% to 65% means more than an hour a day spent in range, which is often easier to picture than a percentage.
The targets
In 2019 an international panel of diabetes specialists agreed on targets for the main CGM numbers. These are the ones most clinics use:
| Measure | Range | Target for most adults | Per day |
|---|---|---|---|
| Time in range | 70–180 mg/dL (3.9–10.0 mmol/L) | More than 70% | More than 16 h 48 min |
| Time below range | Under 70 mg/dL (3.9 mmol/L) | Less than 4% | Less than 1 h |
| Of which very low | Under 54 mg/dL (3.0 mmol/L) | Less than 1% | Less than 15 min |
| Time above range | Over 180 mg/dL (10.0 mmol/L) | Less than 25% | Less than 6 h |
| Of which very high | Over 250 mg/dL (13.9 mmol/L) | Less than 5% | Less than 1 h 12 min |
The same panel set gentler targets for older adults and people at higher risk of lows: more than 50% in range, less than 1% below 70 mg/dL, and less than 10% above 250 mg/dL. During pregnancy with type 1 diabetes, the range itself is tighter, 63 to 140 mg/dL (3.5 to 7.8 mmol/L), with a target of more than 70% in it.
These are starting points. Your own targets are something to agree with your care team, and the time below range matters as much as the time in it: a high TIR that comes with frequent lows isn't the goal.
How time in range relates to A1C
A1C is an average of roughly the last three months. It is useful, but an average can hide a lot: two people can both have an A1C of 7%, one with a steady day and the other swinging between lows and highs. Time in range shows that difference.
The two still move together. Studies have found that a time in range of 70% corresponds on average to an A1C of about 7%, and 50% to about 8%, and that every 10% change in time in range goes with roughly a 0.8 point change in A1C. Lower time in range has also been linked with a higher risk of eye and kidney complications. If you'd like to turn your average glucose into an estimate, our A1C and GMI calculator does it in the browser.
How much data you need
One good or bad day says little. The consensus is to look at at least 14 days of readings, with the sensor worn at least 70% of that time. Comparing one 14-day period with the next is the most useful way to see whether something you changed is working.
What about time in tight range?
Some clinicians now also look at time in tight range, 70 to 140 mg/dL (3.9 to 7.8 mmol/L), which is closer to how glucose behaves without diabetes. In one study of adults without diabetes wearing a CGM, they spent about 96% of the day between 70 and 140. There is no agreed target for people with diabetes yet, so treat it as extra detail rather than a new goal.
Where the easiest gains usually are
Time above range often comes from a handful of repeat situations rather than the whole day. Looking for those patterns is usually more useful than trying to change everything at once:
- Meals that send you high. If the same dish takes you over 180 mg/dL every time, changing the portion, what you pair it with, or when you eat it can win back a lot of minutes.
- The hours after dinner. Evening meals are often bigger, and they are followed by sitting still. A short walk after dinner is one of the simplest things to try.
- Mornings. A rise before breakfast may be the dawn phenomenon, which is worth raising with your care team because the fix is usually about medication.
- Snacks. Small snacks add up, especially sweet ones. Our piece on popcorn and blood sugar shows how much the portion matters.
Time in range in InRange
InRange shows your time in range over 7, 14, 30 or 90 days, together with your average, GMI and variability, the figures a clinician usually reads first. It also gives every dish you log its own time back in range, so you can see which meals cost you the most minutes above 180, and which ones barely move you at all.
Common questions
Is 70% time in range good?
For most adults with type 1 or type 2 diabetes, more than 70% is the consensus target, so yes, as long as the time below range stays low too (under 4%).
What is a normal time in range without diabetes?
People without diabetes spend nearly all of the day between 70 and 180 mg/dL, and in one study about 96% of the day even between 70 and 140 mg/dL.
Is time in range better than A1C?
They answer different questions. A1C is a long average from a blood test; time in range shows how the days actually went, including lows and highs an average can hide. Most clinics now look at both.
How many days of data do I need for time in range?
At least 14 days, with the sensor worn at least 70% of the time.
Sources
- Battelino T, Danne T, Bergenstal RM, et al. Clinical targets for continuous glucose monitoring data interpretation: recommendations from the International Consensus on Time in Range. Diabetes Care. 2019;42(8):1593–1603.
- Beck RW, Bergenstal RM, Riddlesworth TD, et al. Validation of time in range as an outcome measure for diabetes clinical trials. Diabetes Care. 2019;42(3):400–405.
- Vigersky RA, McMahon C. The relationship of hemoglobin A1C to time-in-range in patients with diabetes. Diabetes Technology & Therapeutics. 2019;21(2):81–85.
- Shah VN, DuBose SN, Li Z, et al. Continuous glucose monitoring profiles in healthy nondiabetic participants: a multicenter prospective study. Journal of Clinical Endocrinology & Metabolism. 2019;104(10):4356–4364.
- American Diabetes Association. Standards of Care in Diabetes, section 6: Glycemic goals and hypoglycemia.