The purpose of the study is to determine the efficacy and safety of sitaglipin in the treatment of Type 2 diabetes mellitus (T2DM) patients with inadequate glycemic control using metformin and insulin.

DPP-4 inhibitors enhance function of endogenous incretin that helps with glucose homoeostasis. DPP-4 inhibitors have been proved to promote glycemic control without increasing risk of hypoglycemia and weight gain. In addition, they may improve beta-cell function and do not have any known associations with overt cardiovascular or hepatic safety risks. Addition of sitagliptin to treatment of T2DM patients poorly controlled on insulin +/- metformin has been shown to reduce HbA1c while being generally well-tolerated. It could be clinically useful to add sitaglipin to treatment regimen of T2DM patients on stable therapy with insulin \& metformin. Apart from glycemic reduction, secondary effects like prevention of weight gain, reduction in insulin dose, improved cardiovascular risk profile, etc. may be expected from addition of sitagliptin to treatment.