Hypoglycemia is a common side effect of intensive insulin therapy in patients with type 1 diabetes. Mild hypoglycemia is any episode that can be self-treated, while a severe episode requires external help for recovery. Acute hypoglycemia produces autonomic and neuroglycopenic symptoms, including cognitive impairment and mood changes, while sympathoadrenal stimulation can provoke acute hemodynamic changes with alterations in regional vascular perfusion and a risk of cardiac dysrhythmias. Neurological manifestations include coma, convulsions and focal abnormalities. Long-term morbidities associated with hypoglycemia include impaired awareness of hypoglycemia, counterregulatory hormonal deficiencies, hypoglycemia-associated autonomic failure, and, in rare cases, permanent cognitive impairment. Hypoglycemia affects all aspects of life for the person with type 1 diabetes, including employment, social interactions, driving, sport and leisure activities, and sleep. Appreciation of the potential morbidities of hypoglycemia should encourage physicians to utilize therapeutic regimens that decrease the risk of severe hypoglycemia.