Time in range, and why it beats a single number
Mis à jour 2026-08-07
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Réponse courte
What is time in range?
Time in range is the percentage of the day your glucose spends between 3.9 and 10.0 mmol/L (70–180 mg/dL). It matters because two people can share an HbA1c while one is stable and the other is swinging between highs and lows. In people with diabetes, lower time in range is strongly associated with a higher rate of eye and kidney complications.
Comment lire les étiquettes de preuve
Chaque affirmation de cette page porte une étiquette indiquant le poids qu’elle peut supporter. Elle décrit la solidité du résultat, non le prestige de la revue.
- Preuves solidesUn grand essai randomisé, une cohorte suivie longtemps, ou la concordance de plusieurs d’entre eux.
- Preuves émergentesRéel, mais mince — petit, court, observationnel ou non encore répliqué.
- ContestéDes chercheurs compétents sont en désaccord. Nous ne tranchons pas à votre place.
What an average hides
HbA1c is roughly an average of your glucose over the preceding two to three months. Averages are indifferent to how you got there. A steady person and a person alternating between hypoglycaemia and high peaks can arrive at the same figure, and the second person is not having the same experience or carrying the same risk.
Time in range restores what the average discarded: how much of the day was actually spent where you wanted to be. Its companions — time above range and time below range — say which direction the rest went.
Ce que disent les preuves
International consensus defines the standard target range as 3.9–10.0 mmol/L (70–180 mg/dL) and sets recommended time-in-range targets for diabetic populations.1
Preuves solides
The evidence behind it
Time in range was validated by going back to the Diabetes Control and Complications Trial and asking whether it predicted the outcomes that actually matter. Across 1,440 participants, each 10-percentage-point drop in time in range came with a 64% higher rate of retinopathy progression and a 40% higher rate of developing microalbuminuria.
One caveat belongs with that figure, and it is usually left out. Those trial participants pre-dated continuous monitors: their time in range was computed from seven fingerstick measurements a day, not from a CGM. The association is solid; the exact numbers come from a coarser instrument than the one you would be wearing.
Ce que disent les preuves
Each 10-percentage-point reduction in time in range was associated with a 64% higher hazard of retinopathy progression and a 40% higher hazard of developing microalbuminuria.2
Preuves solides
Those hazard estimates were derived from seven-point daily fingerstick profiles in a trial that predated continuous monitoring, not from CGM data.2
Preuves solides
If you do not have diabetes
The targets are defined for people with diabetes, and there is no validated equivalent for anyone else. An app that shows a metabolically healthy person a time-in-range score is applying a diabetic yardstick outside the population it was built and tested in.
That does not make the number meaningless — it makes it uncalibrated. Treat it as a description of your week rather than a grade.
Ce que disent les preuves
Consensus time-in-range targets were established for diabetic populations; no validated target exists for people without diabetes.1
Preuves solides
What you need to measure it
Any sensor produces a time-in-range figure, but the figure inherits the sensor's sampling rate and its accuracy. A device reading every fifteen minutes has a quarter of the evidence per hour that a one-minute device has, and every reading carries the device's own error.
If time below range is what you care about — the case for anyone taking insulin — alarms matter more than the summary statistic, because a percentage computed at the end of the week cannot wake you up.
Questions fréquentes
- What is a good time in range?
- For most adults with diabetes, consensus guidance sets a target of more than 70% of the day in the 3.9–10.0 mmol/L range, with tighter goals in pregnancy and more relaxed goals for older or high-risk people. There is no validated target for people without diabetes.
- Is time in range better than HbA1c?
- It is complementary. HbA1c remains a valuable long-run measure; time in range adds the distribution the average conceals, and it has been validated against microvascular complications in trial data.
- Does my time in range depend on which sensor I wear?
- Yes, in two ways. Sampling interval determines how many readings the percentage is computed from, and sensor error shifts individual readings across the boundaries. Comparing your figure with someone on a different device is not exact.
Références
- 1.Battelino T, Danne T, Bergenstal RM, Amiel SA, Beck R, Biester T, et al. (2019). Clinical Targets for Continuous Glucose Monitoring Data Interpretation: Recommendations From the International Consensus on Time in Range. Diabetes Care. 10.2337/dci19-0028
- 2.Beck RW, Bergenstal RM, Riddlesworth TD, Kollman C, Li Z, Brown AS, Close KL (2019). Validation of Time in Range as an Outcome Measure for Diabetes Clinical Trials. Diabetes Care. 10.2337/dc18-1444