This article describes the pharmaceutical care of an adolescent with type 1 diabetes mellitus, who took part in the DIADEMA study. Diabetes was diagnosed for three years and his baseline HbA1c-value was 9.3 %. In the DIADEMA study adolescents received pharmaceutical care provided by community pharmacists in addition to usual care provided by diabetologists and diabetes educators. Patients in the intervention group received monthly scheduled visits with the community pharmacists and on-demand telephone calls. Fundamental contents of the pharmacist᾽s interventions were in particular self-monitoring of blood glucose, prevention of acute and long-term diabetes complications and conscientious consumption of alcohol. Furthermore difficulties in individual insulin therapy and current life conditions were addressed.