Rates of administration of enteral carbohydrate to maintain the plasma glucose concentration and suppress organic acidemia in young children with glycogen storage disease Type I have not been clearly established. Therefore, we studied six children with the disease during sequential nasogastric infusions of carbohydrate at four different rates (10.5, 8.6, 5.8, and 3 mg of carbohydrate per kilogram of body weight per minute). The rates at which total and endogenous glucose appeared in the plasma were measured with [2H2] glucose. The infusion rates of carbohydrate were linearly correlated (r = 0.88, P less than 0.001) with the plasma glucose concentration, which was about 90 mg per deciliter at a rate of 8.6 mg per kilogram per minute. The mean (+/- SE) rate of appearance of endogenous glucose was 1.4 +/- 0.1 mg per kilogram per minute at a nasogastric infusion rate of 5.8 mg of carbohydrate per kilogram per minute (a rate similar to that of hepatic glucose production in normal children who have fasted overnight), and was completely suppressed at 10.5 mg of carbohydrate per kilogram per minute. Concentrations of plasma lactate, pyruvate, free fatty acids, and ketone bodies were inversely related to the rate of carbohydrate administration below 8.6 mg per kilogram per minute. We conclude that the minimal nocturnal nasogastric infusion rate of carbohydrate needed to maintain plasma glucose concentrations and minimize organic acidemia in young children with glycogen storage disease Type I is approximately 8 to 9 mg per kilogram per minute.