CYP2C9*14 is assigned decreased function based on moderate evidence in heterozygous patients and in vitro studies. Separate studies of patients on a stable dose of warfarin with CYP2C9 *1/*14 genotype required a lower warfarin dose compared to CYP2C9*1/*1 patients (24956244, 19077919, 15371982). The VKORC1 and CYP4F2 variants associated with increased warfarin dose requirements were also observed in one of these patients which further suggested decreased warfarin metabolism and warfarin dose was due to the CYP2C9 *1/*14 genotype (24956244). In vitro studies similarly found CYP2C9*14 demonstrated decreased clearance of warfarin, phenytoin, tolbutamide, glimepiride, carvedilol, propofol, flurbiprofen, mestranol, diclofenac, and losartan (23752738, 27163851, 16099926, 24077631, 24118918, 25476996, 25832633, 25144335, 25924705, 25951663, 23844998). Although two in vitro studies showed CYP2C9*14 had similar activity compared to wildtype, the experts did not find these results convincing as in these studies CYP2C9*2 and/or CYP2C9*3 which definitively have decreased function and no function, respectively, demonstrated increased activity compared to wildtype in these studies (25142737, 25884291). Therefore, consensus among experts was decreased function with an activity value of 0.5 based on moderate evidence.