We sought to determine whether treatment of hypoglycemia with a snack containing both protein and carbohydrate results in more prolonged protection against subsequent hypoglycemia than ingestion of carbohydrate alone. We studied six insulin-dependent diabetic subjects on two occasions. On both occasions subjects received a variable overnight insulin infusion to achieve euglycemia followed by a constant insulin infusion (approximately 0.5 mU x kg(-1) x min(-1)) designed to produce hypoglycemia. When glucose reached 50 mg/dL, subjects were fed a snack consisting of either bread (approximately 85 kcal) or bread plus meat (approximately 205 kcal). Both contained 15 g of carbohydrate. The insulin infusion was continued for the next 3 h or until glucose again fell to 50 mg/dL. Although bread plus meat resulted in a more marked rise (P < 0.05) in glucagon than did bread alone, neither the post treatment peak glucose concentration (73 +/- 4 vs. 70 +/- 6 mg/dL) nor the subsequent rate of fall of glucose (0.42 +/- 0.10 us. -0.35 +/- 0.07 mg/dL/min) differed. The present study shows that the rate of redevelopment of hypoglycemia does not differ after eating bread or bread plus meat. Therefore treatment of hypoglycemia with a protein-enriched snack merely adds calories rather prolonged protection against subsequent hypoglycemia.