OBJECTIVES: To assess the costs incurred in management and follow-up of severe hypoglycaemic events (SHEs; requiring external help for recovery) in Germany, Spain and the UK. METHODS: In 639 people aged ≥16 years and receiving insulin for type 1 (n=319) or type 2 diabetes (n=320) who experienced ≥1 SHE in the previous 12 months, healthcare resource use was measured for the most recent event via patient surveys. Patients were grouped by where the SHE was treated: Group 1, community (lay person); Group 2, community (health care professional, HCP); Group 3, hospital. Costs were calculated by applying unit costs from published sources to estimated resource use; costs per SHE were calculated by dividing by the number of patients per subgroup. Weighted average costs across all treatment groups were derived using prevalence data from the Roper Starch database. RESULTS: Hospital treatment is a major cost driver for SHEs in all countries, despite most patients being treated in the community. Costs per SHE were similar for type 1 and type 2 patients in all three countries, e.g. in Germany (Groups 1–3 respectively), €52, €482 and €3671 for type 1 diabetes and €30, €354 and €3366 for type 2 diabetes. The average cost per SHE (all patients) for Germany, Spain and UK respectively was €522, €466 and UK£164 (€242*) in type 1 patients and €595, €572 and UK£358 (€527*) in type 2 patients (*€1.00 = UK£0.679; average rate, 2/06–3/07). More patients with Type 2 than Type 1 diabetes are treated by HCPs in the UK, resulting in higher costs. Calls and visits to family doctors, additional glucose testing and education about diabetes management contribute substantially to total costs in non-hospitalised patients. CONCLUSIONS: SHEs add significantly to health care costs. SHE treatment costs were similar in all three countries, despite differences in management approach.