PURPOSE: Mobile applications (apps) have proven to be highly effective tools to empower patients with type 1 diabetes mellitus (T1DM) and enable them to achieve better self-care, quality of life (QOL), and glycemic control. The aim of the study is to examine whether mySugr METHODS: This study concerns an exploratory randomized clinical trial of 12 months' duration. People with T1DM using multiple daily injections were randomized to usual care (bolus calculator, five face-to-face visits) or intervention (mySugr RESULTS: A total of 25 out of 28 participants completed the study (52% men, age 44.52 years, diabetes duration 21.28 years). At 12 months, no significant differences were identified in the change of DES-SF-S and additional PROMs between arms. Similarly, no differences were observed in glucose-related outcomes except for the change in CV at 9 (control - 1.87 ± 4.98 vs. intervention 5.89 ± 11.33, p = 0.008) and 12 months (control - 2.33 ± 3.54 vs. intervention 5.12 ± 11.32, p = 0.018). Adherence to and satisfaction with the app were high. CONCLUSION: Patients with diabetes using the mySugr