CYP2D6*14 is assigned decreased function based on limited evidence. Three subjects with CYP2D6*1/*14, CYP2D6 *10/*14, and CYP2D6*14/*41 genotype, respectively demonstrated decreased dextromethorphan metabolism compared to wildtype based on urine metabolites (19364831). Multiple in vitro studies found CYP2D6*14 had modestly decreased enzyme activity compared to wildtype with various substrates (18784265, 19364831, 24647041, 30366777). Therefore, consensus among experts was decreased function with an activity value of 0.5 based on limited evidence as it was determined the phenotypes containing this allele would be clinically distinct from phenotypes comprising normal function alleles.