Overcoming Closed-Loop System Limits: Diluted Insulin Improves Glycemic Control and Reduces Nighttime Hypoglycemia in Toddlers with Low Insulin Requirements

Background and aim: Very young children with type 1 diabetes (T1D) and low total daily dose (TDD) struggle to achieve optimal glucose control despite hybrid closed-loop (HCL) system. The aim of the study was to evaluate the impact of diluted insulin on glucose control in a real-world setting. Methods: This retrospective multicentric French study included 35 children with T1D (below 6 years of age) using CamAPS FX HCL system. Participants were transitioned from U100 insulin to a diluted formulation (U10, U20, or U50). Clinical and continuous glucose monitoring (CGM) data were collected before (predilution) and at 1, 3, and 6 months postdilution. Comparisons between predilution and each postdilution period were performed using linear mixed models. Results: Participants had a median TDD of 9.7 (7.7–11.4) UI/day before dilution and a suboptimal glucose control. Insulin dilution was associated with a reduction of time below range (TBR 70 ), glucose variability (coefficient of variation) and pump alarms during the night, with TBR 70 decreasing by 3-fold between 4 to 7AM. Transition to diluted insulin led to a significant increase of time in range (TIR 70–180 ) and a decrease of time above range (TAR 180 ) by, respectively, 1.5 h and 1 h per day. These results were observed independently of the time of dilution. No episodes of severe hypoglycemia or ketoacidosis occurred during the follow-up. Conclusions: In very young children with T1D and low TDD who are exhibiting suboptimal glucose control despite HCL, insulin dilution may be a safe and efficient option.