Aims: To describe the characteristics and associated risk factors of patients with established diabetes who required Emergency Department (ED) care for severe hypoglycemia. Methods: We performed an observational retrospective study to identify all cases of severe hypoglycemia among attendees at the EDs of three Italian University hospitals from January 2010 to December 2014. Results: Overall, 520 patients with established diabetes were identified. Mean out-of-hospital blood glucose concentrations at the time of the hypoglycemic event were 2.2 ± 1.3 mmol/L. Most of these patients were frail and had multiple comorbidities. They were treated with oral hypoglycemic drugs (43.6%), insulin (42.8%), or both (13.6%). Among the oral hypoglycemic drugs, glibenclamide (54.5%) and repaglinide (25.7%) were the two most frequently used drugs, followed by glimepiride (11.3%) and gliclazide (7.5%). Hospitalization rates and in-hospital deaths occurred in 35.4% and in 2.3% of patients, respectively. Cirrhosis (odds ratio [OR] 6.76, 95% confidence interval [CI] 1.24–36.8, p