Gastrectomy or vagotomy may result in reactive hypoglycemia, which, in some cases, can reduce the plasma glucose levels to 30-40 mg/dl due to rapid digestion and absorption of food, especially carbohydrates. It also occurs sometimes in patients on hemodialysis, where it is a potentially lethal complication. Because insulin has a longer half-life due to lack of renal degradation, hypoglycemia can be induced by insulin in patients with renal failure. We treated a patient with frequent episodes of severe hypoglycemia, that were sometimes accompanied by convulsions. He had undergone total gastrectomy 8 years before and had been maintained on hemodialysis for 3 years. Hyperinsulinemia caused by oxyhyperglycemia associated with post-gastrectomy led to severe hypoglycemia in this patient because of the lack of renal insulin degradation. Since nutritional treatment did not successfully manage his reactive hypoglycemia, an alpha-glucosidase inhibitor, acarbose, was administered to treat his oxyhyperglycemia. This therapy was very effective and he has not had any recurrence of reactive hypoglycemia since the initiation of the therapy.