Inherited metabolic diseases (IMD) form a heterogeneous group of genetic disorders that surface primarily during childhood and result in significant morbidity and mortality. A prevalence of 1 in 2500–5000 live births is often reported. The transfer of adolescents from pediatric care to adult health facilities is often difficult for patients and their families and can lead to a breakdown in medical follow-up and therefore serious complications. Existing recommendations for the successful transition of patients with chronic disorders do not specifically address patients with IMDs associated with dietary treatment. Here, the French network for rare inherited metabolic diseases (G2M) presents its reflections and recommendations for a successful transition. Preparations for the transfer must be made well in advance. The transfer must aim for adolescents gaining autonomy by making them responsible and providing them with the knowledge that will enable them to manage their care themselves, know how to react appropriately if there is any change in their condition, and move comfortably within the adult healthcare system. This requires the active participation of the patient, his or her family, and pediatric and adult care teams. It involves multidisciplinary management plus the production and maintenance of an educational therapy program. Finally, the identification of physicians and dietitians trained in IMDs, relevant subspecialists, and even expert patients could improve the continuum of complete and appropriate care for these patients within adult medicine.