CYP2D6*100 is assigned no function based on limited evidence. CYP2D6*100 has been described in a subject with CYP2D6*5/*100 genotype demonstrating markedly decreased dextromethorphan metabolism compared to wildtype (23394389). CYP2D6*100 is defined by the same SNPs as CYP2D6*10 in addition to a base pair deletion resulting in a frameshift yielding a nonfunctional protein. Therefore, consensus among experts was no function with an activity value of 0 based on limited evidence.