This study is conducted in Europe. The aim of this observational study is to investigate the effect of switch from other basal insulin treatments to Levemir® on body weight in obese diabetic patients. A local extension will be conducted in Slovenia in order to reach the planned 400 patients for the sub-analysis of Slovenian patients.

Included in the study is a retrospective part to evaluate the weight progress since initiation of insulin treatment of another basal insulin and/or oral antidiabetic drugs (OAD) and/or bolus insulin therapy. Retrospective data will be collected at baseline and at approximately 6 and 12 months before starting insulin detemir therapy.

Inclusion Criteria:

• Diabetes mellitus (Type 1 or type 2)
• BMI greater than 27 kg/m^2, or more than 3 kg weight increase since start of insulin therapy

Exclusion Criteria:

• Subjects currently being treated with insulin detemir
• Subjects who were previously enrolled in this study;
• Subjects with a hypersensitivity to insulin detemir or to any of the excipients.
• Women who are pregnant, breast feeding or have the intention of becoming pregnant within next 12 months Female patients will be reminded to use adequate contraceptive during the study, where is relevant.

Patients from both general and speciality practice settings who have been deemed appropriate to receive Levemir® because of weight increase on other insulin therapies, and as part of routine out-patient care by the prescribing physician.