DPP4 inhibitors also have better safety and tolerability profiles (e.g., weight neutrality and less hypoglycemia) compared to other hypoglycemic agents. When considering combination therapy with DPP-4 inhibitors, metformin is the most commonly used agent which has been shown to be effective and well tolerated from previous studies. Besides the glucose lowering effect by reducing hepatic glucose output and improving insulin resistance, metformin without inhibiting DPP-4 activity,also increases active GLP-1 concentrations by 1.5- to 2-fold following an oral glucose load in obese, nondiabetic subjects. Accordingly, this effect of metformin may provide a unique benefit when combined with DPP-4 inhibitors through a substantial enhancement of the incretin axis, which provides effective and potentially additive glycemic improvement.