Background: The insulin analogs, glargine and detemir, are associated with reduced hypoglycemia incidence compared with NPH insulin. We assessed the impact of changing basal insulin from NPH to glargine or detemir in patients with type 1 diabetes mellitus who experienced severe hypoglycemia. Material and methods: A retrospective chart review was conducted that included 73 (31 female) patients (mean age 48 years, diabetes duration 19 years) treated for 12 to 24 months with insulin glargine (n = 43) or detemir (n = 30). Results: There were no patients who withdrew from treatment due to side effects. The mean treatment duration in both groups was 18 months. Changing from NPH insulin was associated with a −0.3% (p = 0.036) reduction in HbA1c for glargine (baseline 8.8%) and −0.4% (p = 0.040) for detemir (baseline 8.3%) treated patients; insulin dosages increased, respectively by 4.1 (p = 0.045) and 4.3 units (p = 0.004) (mean values). Weight did not increase significantly and the 1-year rate of serious hypoglycemia was 0.25/person/year. Conclusion: Switching from NPH-insulin to insulin detemir or glargine in type 1 diabetes mellitus patients with previous serious hypoglycemia was associated with a reduction in HbA1c. However, severe hypoglycemia was not completely eliminated, and few patients reached internationally accepted glycemic treatment goals. Literature search: We searched Medline, PubMed (with key search terms type 1 diabetes, NPH insulin, detemir, glargine and serious hypoglycemia), reference lists and databases of ongoing and completed trials (through July 2008) provided from the manufacturers of the drugs to identify relevant literature.