BACKGROUND: Managing bolus insulin dosing can be a significant burden for people with diabetes, many of whom have limited numeracy skills. Insulin bolus calculators (IBCs) may improve glycemia as well as treatment satisfaction. OBJECTIVE: The purpose of this study was to demonstrate the safety of a novel, continuous glucose monitoring (CGM)-informed IBC mobile device app that applies trend arrow adjustments to bolus insulin dose recommendations. RESEARCH DESIGN AND METHODS: This clinical trial was an open-label, industry-sponsored single-arm study conducted at two sites. Fifty-four participants with type 1 or type 2 diabetes were enrolled and used the IBC app on their mobile device for 30 days. Study participants were adults who were already using CGM and dosing bolus insulin. The analysis examined both noninferiority and superiority of time in range (TIR) during the study period compared with baseline. Other important end points included hypoglycemia, glucose variability, nocturnal and diurnal TIR, and diabetes distress. The per-protocol (PP) group was defined as participants who used the IBC >
30 times during the study. RESULTS: Mean TIR improved by 3.8% (95% CI 0.7-6.9%) from 69.2 to 73.0% ( CONCLUSION: A CGM-informed IBC app that applies trend arrow adjustments to bolus insulin dose recommendations improved TIR without increasing hypoglycemia or diabetes distress in individuals with type 1 or type 2 diabetes.