Treatment with diazoxide at a high dose of 20 mg/kg/day failed to control the hypoglycemia: the plasma glucose fell to 50 mg/dl (2.8 mmol/l) after only 5 hr of fasting with suppressed plasma beta‐hydroxybutyrate concentration (0.82 mmol/l) and an inappropriately large glycemic response to glucagon (delta 40 mg/dl). The gene discussed is GCG; the disease is Hypoglycemia.