CYP2C19*15 is assigned normal function based on limited evidence. Two in vitro studies using different cell systems found CYP2C19*15 demonstrated similar enzyme activity compared to wildtype with mephenytoin and omeprazole substrates (21325430, 25001882). Therefore, consensus among experts was normal function based on limited evidence as it was determined the phenotypes containing this allele would be clinically similar to phenotypes comprising normal function alleles.