Each 10% more time in range tracks lower mortality

HbA1c has long been the standard yardstick for glucose control, but it is an average that hides how much of the day someone actually spends within a healthy glucose window. Time in range, derived from glucose monitoring, captures that directly, and the rise of continuous and flash sensors has made it widely available. What has been less certain is whether time in range predicts hard clinical outcomes in type 2 diabetes, or merely describes day-to-day control. This review set out to quantify its prognostic value across the complications that matter most.

The authors searched PubMed, Embase and the Cochrane Central Register from 2017 to November 2025 for studies relating time in range to clinically relevant outcomes in people with type 2 diabetes, including data from continuous glucose monitoring, flash glucose monitoring and fingertip capillary testing. Twenty-four observational studies covering 20 distinct associations and 35,916 participants were included. Extracted data were standardised so every result expressed the effect of a 10% increment in time in range. Pooled estimates used inverse-variance random-effects models with dose-response analysis, and dose-response meta-analyses were possible for nine of the associations. Certainty of evidence was appraised using the GRADE framework.

Each 10% increment in time in range was associated with lower all-cause mortality, with an odds ratio of 0.88 (95% confidence interval 0.82 to 0.93). The same increment was associated with reduced risk of diabetic retinopathy (odds ratio 0.92) and vision-threatening retinopathy (0.93), lower extremity atherosclerotic disease (0.86), diabetic peripheral neuropathy (0.77) and cardiovascular autonomic neuropathy (0.81). The largest apparent effect was for peripheral neuropathy, the smallest for retinopathy outcomes. Not everything moved: associations with albuminuria at KDIGO categories A2 and A3, and with amputation, did not reach statistical significance in the primary meta-analysis. The authors conclude time in range looks like a robust prognostic indicator and a target worth acting on.

This extends the case that how glucose behaves across the day carries information beyond a single averaged laboratory value, and it does so with a consistent dose-response pattern across several complication types. Because every included study was observational, it cannot separate time in range as a cause from time in range as a marker of better overall health, care and adherence. The null results for albuminuria and amputation leave open whether those outcomes genuinely differ or were simply underpowered. Interventional evidence that deliberately raising time in range changes mortality is still the missing piece.

If you or someone you care for uses a glucose sensor, this is a reason to treat the proportion of the day spent in range as meaningful information rather than a novelty metric alongside HbA1c. The pattern is graded, meaning incremental improvements track with incremental risk reduction rather than there being a single cliff edge. It does not prove that pushing the number up will itself prevent complications, and the kidney and amputation findings were not significant. How glucose targets apply to an individual is a matter for the clinical team, not a self-set goal.