Hypoglycemia is the most common endocrinologic problem seen in emergency departments. To explore its causes in patients who admitted to the emergency department with symptoms resembling hypoglycemia, 225 hypoglycemia cases were evaluated from January 2000 to May 2008. Of 225 hypoglycemia cases, 158 (70.2%) were receiving treatment for diabetes mellitus, which was the most common group (94 patients were using insulin, 55 were receiving oral anti-diabetics (OAD) and 9 patients both OAD and insulin). The other causes for hypoglycemia were as follows: reactive hypoglycemia cases (11.6%), insulinoma (2.7%), malignancies (2.2%), Sheehan syndrome (0.9%), chronic liver disease (0.9%), gestational diabetes mellitus (0.4%), OAD use by mistake (3.6%), and use of OAD for suicidal purposes (13%). In eight of the cases, the reason could not be identified. The study revealed that diabetes mellitus constitute the most common reason for hypoglycemia among the patients seen in emergency departments. Efforts should be made to prevent hypoglycemia by giving the patients better education.