CYP2C9*17 is assigned uncertain function based on inadequate evidence due to conflicting in vitro data and no clinical data. In an in vitro study CYP2C9*17 demonstrated 32% warfarin clearance compared to wildtype, however, similar tolbutamide clearance compared to wildtype was demonstrated in the same study as well as a separate study (23752738, 16099926). Therefore, consensus among experts was not achieved and uncertain function was assigned.