All oral anti-diabetic drug (OAD) treatment will be discontinued when trial participant enters the main trial (NN1250-3579) with the exception of metformin and dipeptidyl peptidase-IV (DPP-IV) inhibitor treatment (only in countries where DPP-IV inhibitor treatment is approved for combination treatment together with insulin, otherwise DPP-IV inhibitor treatment is also discontinued). Subjects who consent to participate in the extension trial will continue the treatment (NN1250 or insulin glargine + oral antidiabetic drugs (OADs)) to which they were randomly allocated in the 52 week main trial.