A Multicenter, Randomized, Active-controlled, Parallel-group Study to Assess the Efficacy and Safety of Insuman Comb 25 (Insulin Human) Versus Novolin® 30R Twice Daily Over 24 Weeks in Patients With Type 2 Diabetes Mellitus Who Are Under Insulin Therapy

Primary Objective: To compare the efficacy of Insuman Comb 25 versus Novolin® 30R on HbA1c reduction during a 24-week treatment period in patients with type 2 diabetes mellitus. Secondary Objectives: - To assess the effects of Insuman Comb 25 versus Novolin® 30R in patients with type 2 diabetes mellitus on fasting plasma glucose (FPG) - To assess the safety and tolerability of Insuman Comb 25 versus Novolin® 30R in patients with type 2 diabetes mellitus