Ketosis is a state of elevated levels of ketone bodies in the body. Ketone bodies are formed by ketogenesis when liver glycogen stores are depleted. The ketone bodies, acetoacetate and hydroxybutyrate, are used for energy. Entering a state of ketosis requires limiting the intake of the number of carbohydrates to 20 grams or fewer per day. This article discusses how a ketogenic diet may benefit bipolar patients and also its limitations.