Background: To review the available evidence from prospective studies on the safety and tolerability of the ketogenic diet (KD) for the treatment of refractory childhood epilepsy.

Methods: A comprehensive bibliographic search was performed with the aim of retrieving prospective studies that monitored adverse effects (AEs) in children after receiving the classic or medium-chain triglyceride KD therapy for refractory epilepsy.

Results: A total of 45 studies were retrieved, including 7 randomized controlled trials. More than 40 categories of AEs were reported. The most common AEs included gastrointestinal disturbances (40.6%), hyperlipidemia (12.8%), hyperuricemia (4.4%), lethargy (4.1%), infectious diseases (3.8%) and hypoproteinemia (3.8%). Severe AEs, such as respiratory failure and pancreatitis, occurred in no more than 0.5% of children. Specifically, patients receiving KD therapy should be monitored for osteopenia, urological stones, right ventricular diastolic dysfunction, and growth disturbance. The total retention rates of the diet for 1 year and 2 years were 45.7% and 29.2%, respectively. Nearly half of the patients discontinued the diet because of lack of efficacy. AEs were not the main reason for the KD discontinuation. None of the 24 deaths reported after initiation of the diet was attributed to the KD.