Elizabeth G Neal 1Matthew's Friends Clinics, Lingfield, UK, 2UCL Institute of Child Health, London, UK Abstract: The ketogenic diet (KD) is a high-fat, restricted-carbohydrate regime, originally designed to mimic metabolic responses to fasting and has been used since the 1920s as a treatment for epilepsy. Modified variants of the KD include the addition of medium-chain triglyceride and less-restrictive modified Atkins and low glycemic index protocols. Scientifically proven as treatment for intractable seizures in children, these ketone-generating diets are increasingly also being used in adults. They are the treatment of choice in glucose transporter type 1 deficiency syndrome and pyruvate dehydrogenase deficiency. Evidence for the potential of KD therapy to be included within the treatment options for cancer and neurodegenerative disorders is more limited, albeit an exciting area of research with future clinical potential. This review discusses the key aspects of KD therapy, including the efficacy of treatments and clinical implementation. The importance of appropriate initiation, adequate clinical supervision, regular monitoring, and assessment of nutritional needs is highlighted. Keywords: diet, seizures, ketosis