CYP2D6*34 is assigned normal function based on limited evidence. CYP2D6*34 is defined by a common SNP found in more than 50 different CYP2D6 alleles including CYP2D6*2 which is assigned normal function. An in vitro study found CYP2D6*34 had similar enzyme activity compared to wildtype with dextromethorphan and bufuralol substrates (24647041). Although CYP2D6*34 demonstrated decreased enzyme activity with other substrates (24647041, 30366777), the experts did not find this result convincing that the magnitude of decreased activity was clinically significant. Therefore, consensus among experts was normal function with an activity value of 1 based on limited evidence.