CYP2C9*24 is assigned decreased function based on limited evidence in a heterozygous patient and in vitro studies. A patient on a stable dose of warfarin with CYP2C9 *2/*24 genotype had the lowest daily warfarin dose requirement and warfarin clearance based on plasma concentrations compared to patients with CYP2C9 *1/*2 genotype and matched for age, warfarin indication and co-administrated medications (16543980). An in vitro study similarly found CYP2C9*24 exhibited no enzyme activity with warfarin or tolbutamide substrates (23752738). No CYP2C9*24 protein was detected in a separate in vitro study suggesting the enzyme may be improperly folded (17332144). 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.