Comparison of Subject-driven Titration of Biphasic Insulin Aspart (BIAsp) 30 Twice Daily Versus Investigator-driven Titration of BIAsp 30 Twice Daily Both in Combination With Oral Antidiabetic Drugs in Subjects With Type 2 Diabetes

Inclusion Criteria: * Informed consent obtained before any trial-related activities. Trial-related activities are any procedures that are carried out as part of the trial, including activities to determine suitability for the trial * Type 2 diabetes mellitus (diagnosed clinically) for at least 12 months * Currently treated with premixed/self-mixed human insulin (proportion of short-acting insulin is equal to or lower than 30%) BID (twice daily) combined with metformin with or without alpha-glucosidase inhibitor for at least 3 months prior to screening visit (Visit 1) with the minimum dose stated: Metformin: at least 1500 mg/day or maximum tolerated dose at least 1000 mg/day (with unchanged dosing within 3 months prior to Visit 1) OR alpha-glucosidase inhibitors: acarbose or miglitol at least 150 mg/day, or voglibose at least 0.6 mg/day * Total daily insulin dose below 1.4 IU/Kg * HbA1c above or equal to 7.0% and below or equal to 9.5% (central laboratory) * Body Mass Index (BMI) below or equal to 35.0 kg/m\^2 Exclusion Criteria: * Treatment with any insulin secretagogue, thiazolidinedione (TZD), dipeptidyl peptidase-4 (DPP-4) inhibitors and Glucagon-like peptide-1 (GLP-1) receptor agonists within the last 3 months prior to Visit 1 * Previous use of insulin intensification treatment (premixed insulin thrice daily, basal bolus regimen, and continuous subcutaneous insulin infusion (CSII)) for more than 14 days * Previous use of any insulin other than premixed/self-mixed human insulin (proportion of short acting insulin equal to or lower than 30%) BID within 3 month prior to Visit 1 * Recurrent severe hypoglycaemia (more than 1 severe hypoglycaemic episode, during the last 12 months) or hypoglycaemic unawareness as judged by the investigator or hospitalisation for diabetic ketoacidosis during the previous 6 months * Known proliferative retinopathy or maculopathy requiring treatment