The hallmark of type 2 diabetes is insulin resistance and insufficient insulin secretion, and appropriate therapy should be selected for each patient. In this study, to establish some index to select suitable therapy for each patient, we evaluated insulin sensitivity and insulin secretion with euglycemic hyperinsulinemic clamp and hyperglycemic clamp tests, respectively, and found that specific GIR index (GIRxIRI (90)) could be a useful marker to select suitable therapy for each type 2 diabetic patient (GIR: glucose infusion rate in euglycemic hyperinsulinemic clamp test; IRI (90): plasma insulin level 90 min after starting the hyperglycemic clamp test).