Beyond Glycated Hemoglobin: Changes in Time in Range Following Structured Carbohydrate-Counting Education in Adults with Type 1 Diabetes

Background/Objectives: Carbohydrate counting is recommended for adults with type 1 diabetes using flexible prandial insulin, but its association with continuous glucose monitoring (CGM) metrics in adults already using CGM is less well characterized. We evaluated changes in time in range (TIR), glycemic variability, and glycated hemoglobin (HbA1c) following dietitian-led structured carbohydrate-counting education. Methods: In this 12-week single-arm pre–post study, 38 adults with type 1 diabetes using CGM were enrolled in an eight-visit, three-level education program and 30 completed the 12-week follow-up; all analyses are completers analyses restricted to these 30 participants. Fourteen-day CGM metrics, HbA1c, insulin doses, anthropometric measures, and dietary intake were assessed at baseline and week 12. TIR (70–180 mg/dL) was designated the primary outcome after data collection and analysis, so this designation is post hoc. Results: TIR increased from 62.5% ± 14.9% to 73.0% ± 10.9% (mean difference +10.4 percentage points, 95% CI 7.1 to 13.8; p < 0.001). Time above range decreased at 181–250 mg/dL (p = 0.002) and >250 mg/dL (p < 0.001), and HbA1c decreased from 7.71% ± 1.17% to 7.08% ± 0.57% (p < 0.001), without an increase in time below range. The coefficient of variation was lower at week 12 than at baseline (35.7% to 33.6%; p = 0.029), although mean baseline variability was already below the recommended 36% threshold; this difference was not statistically significant in a sensitivity analysis restricted to participants meeting the body mass index eligibility criterion (n = 22; p = 0.179). No increase in body weight or total daily insulin dose was detected. Conclusions: In this uncontrolled study, structured carbohydrate-counting education was associated with higher TIR and lower HbA1c without an increase in time below range. These findings are hypothesis-generating and require confirmation in controlled studies.