Öztürk Z, Gönç EN, Akcan L, Kesici S, Ertuğrul I, Bayrakçı B. Arare but important adverse effect of tacrolimus in a heart transplant recipient:diabetic ketoacidosis. Turk J Pediatr 2015; 57: 533-535.Heart transplantation indications in pediatric population include congenitalheart diseases, cardiomyopathies and retransplants. Cardiomyopathy isthe primary indication for 11 to 17 years of age. The surveillance aftertransplantation is a very important issue because of both the rejectionrisk and the adverse effects due to medications after transplantation.Immunosuppressive agents that are commonly used after heart transplantationshave several toxicities. Here we present an adolescent patient diagnosedwith dilated cardiomyopathy, performed heart transplantation, treated withtacrolimus and suffered from diabetic ketoacidosis due to tacrolimus. Afterthe diagnosis was made the appropriate fluid and insulin therapy was startedimmediately and ketoacidosis resolved in the first 24 hours of the therapy.The diagnosis revised as new onset diabetes mellitus after transplantationand the tacrolimus dosage titrated to therapeutic level. After glycemic controlthe patient discharged with rapid acting insulin, three times daily, beforemeals; and long acting insulin once daily at night. In ten month follow uptime the insulin dosages were progressively reduced.