Individual demographic characteristics, such as age, gender, ethnicity, or poor compliance are known to influence tacrolimus Cmin [11], as are genetic polymorphisms of CYP3A4/5 [12], co-medication with a 3A4/5 inducer or inhibitor [13], or liver dysfunction [14] due to the extensive cytochrome P450 3A4/5-dependent pathway of tacrolimus metabolism [15]. The gene discussed is CYP3A4; the disease is Decreased liver function.