CYP2D6*13 is assigned no function based on limited evidence. CYP2D6*13 was first described in a subject demonstrating markedly decreased dextromethorphan metabolism (8554938). CYP2D6*13 is a CYP2D7-CYP2D6 hybrid allele resulting in a premature stop codon and yielding a truncated nonfunctional enzyme. 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.