CYP2C19*14 is assigned uncertain function due to inadequate evidence. CYP2C19*14 demonstrated similar enzyme activity compared to wildtype with mephenytoin, omeprazole, and other substrates (21325430, 21692664). In a separate in vitro study CYP2C19*14 demonstrated decreased activity compared to wildtype with mephenytoin and clopidogrel substrates (25001882). Therefore, consensus among experts was not achieved and uncertain function was assigned.