CYP2C9*34 is assigned uncertain function due to inadequate evidence. Although one subject with CYP2C9*1/*34 genotype exhibited decreased clearance compared to wildtype subjects based on tolbutamide plasma concentrations after one 500mg dose (25614704), in vitro studies found CYP2C9*34 demonstrated enzyme activity ranging from decreased to increased compared to wildtype with various substrates (23752738, 18971529, 23844998, 19541829, 24118918, 25142737, 25476996, 25614704, 25832633, 25884291, 25924705, 27163851, 24077631, 25144335, 25951663). Consensus was not achieved among experts and therefore uncertain function was assigned..