Hypoglycemia is one of the most important complications of diabetes treatment. The risk of severe hypoglycemia is higher in elderly patients, those having comorbidities such as vascular disease or renal failure, pregnant women and in children with type 1diabetes. Moreover, in type 2 diabetes, progressive insulin deficiency, longer duration of diabetes, and tight glycemic control increase the risk of hypoglycemia as much as type 1 diabetes.Episodes hypoglycemia may lead to impairment of counter-regulatory system, with the potential of development of hypoglycemia unawareness. So, hypoglycemia may increase the vascular events even death in addition to other possible detrimental effects. Glycemic control should be individualized based on patient characteristics with some degree of safety. Recognition of hypoglycemia risk factors, blood glucose monitoring, selection of appropriate regimens and educational programs for healthcare professionals and patients with diabetes are the major issues to maintain good glycemic control, minimize the risk of hypoglycemia, and prevent long- term complications.