Fifty-three diabetic patients were admitted to our hospital for hypoglycemia due to the side effects of sulfonylureas or insulin between January 2008 and March 2012. We retrospectively analyzed these cases based on the patients' clinical records. Forty-one patients were treated with sulfonylureas (SU group), while 12 received insulin (insulin group). The patients in the SU group were older than those in the insulin group, with a mean age of 83.0±8.7 and 74.8±10.8 years, respectively. The mean HbA1c (NGSP) level was lower in the SU group than in the insulin group (6.56±1.19 %vs. 7.64±1.20 %, respectively). The SU group required a significantly longer time for recovery from hypoglycemia than the insulin group (17:[6, 27] hours, 1.5:[1, 8.25] hours, respectively). The majority of patients in the SU group were over 80 years of age, with a serum creatinine level above 1.0 mg/dl or an eGFR below 60 ml/min/1.73 m². Sulfonylureas should be applied carefully in elderly patients, taking into consideration changes to other oral antidiabetic drugs and/or insulin agents. In addition, clinicians should reconsider the target HbA1c level according to the patient's age and provide intensive education regarding coping methods for sick days.