CYP2C9*37 is assigned decreased function based on limited evidence. Multiple in vitro studies found CYP2C9*37 demonstrated decreased clearance compared to wildtype with multiple substrates (24077631, 24118918, 25951663, 25476996, 25832633, 25924705, 27163851, 23844998). Although two in vitro studies showed CYP2C9*37 had similar activity compared to wildtype, the experts did not find these results convincing as in these studies CYP2C9*3 which definitively has no function, demonstrated increased activity compared to wildtype in these studies (25142737, 25884291). An additional in vitro study showed CYP2C9*37 had similar activity compared to wildtype (25144335), however, the experts did not find this result convincing as the function of CYP2C9*37 demonstrated decreased function toward the majority of substrates. Therefore, consensus among experts was decreased function with an activity value of 0.5 based on limited evidence as it was determined the phenotypes containing this allele would be clinically distinct from phenotypes comprising normal function alleles.