We recently encountered a 35-year old man who suffered from frequent hypoglycemia. His blood test revealed the presence of high and suppressed level of insulin with supressed C-peptide levels, hypothalamic-pituitary axis was normal response in hypoglycemia and negative for anti-insulin antibody. Endocrinological and imaging data eliminated the possibility of insulinoma. His symptoms responded well to the therapy of prednisolone (60 mg/day) and plasmapheresis. We followed up the patient over the subsequent 6 months without remarkable lesions. He has had no further recurrences of hypoglycemia. We believe that the antiinsulin receptor antibody might have induced hypoglycemia in this patient. (C) 2012 Elsevier Ltd. All rights reserved.