This randomized controlled study aims to evaluate the effect of mobile application-supported education based on the Health Promotion Model on diabetes management in adolescents aged 12-18 years with Type 1 Diabetes Mellitus. The study will be conducted in a pediatric endocrinology clinic. Participants will be randomly assigned to intervention and control groups. The intervention group will receive mobile application-based diabetes education, while the control group will receive standard care. Outcomes of the study include diabetes knowledge level, self-efficacy, blood glucose monitoring skills, and HbA1c levels.