Prevalence, duration, and clinical implications of continuous glucose monitor measurement limit capping in type 1 diabetes
Authors' conclusion
Sensor limit capping is near-universal in type 1 diabetes, produces sustained periods of right-censored glucose data disproportionately affecting younger participants, and does not substantially distort standard summary metrics at the population level.
Study context
- Population
- Participants with T1D in four publicly available clinical trial datasets4 trial datasets
- Participants
- 948 participants
Methodological detailsretrospective analysis of CGM readings, Dexcom G4 Platinum or G6 sensors
- Retrospective analysis of CGM readings
- Dexcom G4 Platinum or G6 sensors
Primary result
As reported in the abstract
CGM measurement limit capping
- Participants with at least one capped reading
- 93.5% and 100%
- Capped values as share of all readings
- 0.47-0.98%
- Upper-cap runs exceeding 15 min (three datasets)
- over 70%
- Upper-cap runs exceeding 60 min (three datasets)
- over one third
Further findings
Association of upper-limit capping with age
- Inverse association with age in three datasets, Spearman ρ
- −0.20 to −0.47, p ≤ 0.002
Association of upper-limit capping with baseline HbA1c
- Positive association with baseline HbA1c in all four datasets, ρ
- 0.39-0.62, p < 0.001
Capping burden and CGM-BGM divergence (Replace-BG CGM-plus-BGM arm, 77 participants, 1162 14-day windows)
- Capping burden did not predict CGM-BGM divergence in any summary metric
- all p > 0.2
- Systematic CGM-BGM offset in mean glucose and time in range (TIR) reflected physiological lag between blood and interstitial fluid rather than capping artefact
- Within-participant analysis
Original publication
Prevalence, duration, and clinical implications of continuous glucose monitor measurement limit capping in type 1 diabetes. Diabet Med. Published 2 July 2026. doi:10.
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