diagnosis of type 2 diabetes mellitus at the discretion of the investigator for at least 26 weeks prior to screening (visit 1)

treatment with basal insulin for at least 12 weeks prior to randomisation with or without metformin, sulphonylurea (su)/glinide, dpp-4 inhibitors, alfa-glucosidase-inhibitors

hba1c 7.0% - 10.0%

body mass index (bmi) less than or equal to 40.0 kg/m^2

treatment with glucose-lowering agent(s) other than those stated in the inclusion criteria

stroke; heart failure new york heart association (nyha) class iii or iv; myocardial infarction; unstable angina pectoris; or coronary arterial bypass graft or angioplasty

chronic disorder or disease which might jeopardise safety or compliance

malignant neoplasms

recurrent severe hypoglycaemia