SummaryContinuous nocturnal intragastric feeding, combined with frequent daytime feedings, has been reported to improve both linear growth and the metabolic abnormalities in patients with glucose-6-phosphatase deficiency (Type I Glycogen Storage Disease). However, elevated blood levels of lactate have persisted. The present studies explore the relationship between blood lactate concentrations in six patients with glucose-6-phosphatase deficiency and variations in the rate and composition of the intragastric feeding. Blood lactate and plasma glucose concentrations were determined at rates of dextrose administration ranging from 3–34 mg/kg/min. Dextrose infusion at 100–200% of estimated normal glucose production rates gave the best control of blood lactate concentrations. Lower rates of dextrose infusion resulted in significantly higher blood lactate levels; higher rates produced hyperglycemia, but no significant further reduction of blood lactate. At identical rates of glucose administration, a dextrose-containing infant formula and a high carbohydrate enteric feeding solution gave no significant improvement hi control of blood lactate levels compared to dextrose alone. Plasma glucose levels fell more rapidly when intragastric feeding was stopped than after a mixed meal and hypoglycemia appeared to develop before counter-regulatory responses could be mobilized. These observations may account for the increased susceptibility to symptomatic hypoglycemia reported in patients treated with intragastric feeding.SpeculationThese results indicate that intragastric glucose infusion at a rate equal to or slightly greater than normal hepatic glucose production gives maximal control of the metabolic abnormalities in patients with glucose-6-phosphatase deficiency. Complete normalization of hyperlactatemia and hypertriglyceridemia in these patients may require the development of additional forms of therapy.