The effects of diet-induced ketosis on the signs of hypoglycemia were investigated. Lard, medium chain triglycerides, or 1,3-butylene glycol comprised 43% of the diet fed to mice. The diet containing lard or medium chain triglycerides greatly protected the animals from the manifestations of acute insulin-induced hypoglycemia. Furthermore, both diets protected the animals from the effects of repeated insulin injections (every eight hours) for 10 days. In contrast, 1,3-butylene glycol had no protective effects. These experiments suggest that ketogenic diets may be of value in the treatment of recurrent hypoglycemic conditions.