CYP2C9*25 is assigned no function based on limited evidence. CYP2C9*25 is defined by a deletion which leads to a frameshift resulting in an early stop codon and truncated protein. This was demonstrated in an in vitro study where CYP2C9*25 had similar mRNA levels compared to wildtype but no protein expression (16788382). CYP2C9*25 was not included in subsequent in vitro studies because it is it is a null allele resulting in no protein formation (23752738). Therefore, consensus among experts was no function with an activity value of 0 based on limited evidence as it was determined the phenotypes containing this allele would be clinically distinct from phenotypes comprising normal and decreased function alleles.