This trial will be conducted in Africa, Asia, North America and South America. The aim of this clinical trial is to compare NN1250 (insulin degludec) with sitagliptin, as add-on to subject's own current oral antidiabetic (OAD) treatment, in subjects with type 2 diabetes inadequately controlled with 1-2 OADs (metformin, sulphonylurea, glinides or pioglitazone).