Blood samples were collected for the analysis of trough SDC (immunofluorescence) and the polymorphisms of OATP1B1 388A>G, OATP1B1 521T>C, and OATP1B3 699G>A (PCR-RFLP and Sanger sequencing).Patients with glomerular filtration rate (GFR) under 30 mL/min had significantly higher trough SDC (1.20 ± 0.50 ng/mL) than recommended trough SDC for heart failure patients.