1.1. Type 1 diabetes mellitus 1.2. Treatment with any other insulin than LANTUS during the past 6 months in Group LANTUS+MET or with any kind of insulin during the past 3 months in Group SU+MET or Group DPP-4+MET before entering the study 1.3. Treatment with any kind of OAD except MET during the past 6 months in Group LANTUS+MET or with any kind of OAD except MET+SU during the past 3 months in Group SU+MET or with any kind of OAD except DPP-4+SU during the past 3 months in Group DPP-4+MET before entering the study 1.4. Major micro- or macro vascular complications as judged by the investigator