The CYP3A5*6 allele has been assigned as a no function allele by CPIC. Patients who are recipients of a kidney, heart, lung or hematopoietic stem cell transplant or a liver transplant with the same CYP3A5 genotype as the recipient and who carry the *6 allele in combination with another no function allele may have decreased metabolism of tacrolimus as compared to patients carrying two normal function alleles or a normal function allele in combination with a no function allele. This annotation only covers the pharmacokinetic relationship between CYP3A5 and tacrolimus and does not include evidence about clinical outcomes. Other genetic and clinical factors may also affect tacrolimus metabolism.