ABSTRACT The transition of young type 1 diabetic (T1D) patients from pediatric to adult healthcare is a high‐risk period of loss to follow‐up. Since 2015, we have implemented a transition program, involving both pediatric and adult clinicians. The main objective was to evaluate the number of patients who had succeeded this transition program at 1 year. We found that 86% of patients underwent the complete transition program. However, adverse outcomes occurred in 19.1% of patients at 1 year but decreased to 2.9% after 3 years. In 63% of patients their HbA1c level had deteriorated 1 year after the transition day and this level stabilized at around 8% in the following 2 and 3 years. In patients who had improved HbA1c levels the body mass index was lower ( P = 0.03) and they lived alone ( P = 0.04). Although our program seemed to allow a better follow‐up than previously described, this study highlights the importance of further supporting this transition period.