AIM: To investigate the risk factors affecting serum digoxin concentration and the relationship between the level of the concentration and adverse reactions (ADR), and to provide a basis for the safe and rational use of digoxin. METHODS: The serum digoxin concentration (SDC) was monitored by enzyme amplification immunoassay technology. The basic data, laboratory indicators, concomitant medication and adverse reactions of patients were collected through the medical record system. RESULTS: Among the 55 patients, 12.73%, 76.36% and 10.91% of the patients were treated with < 0.125 mg/d, 0.125 mg/d and 0.25 mg/d digoxin, respectively. And the serum digoxin concentration increased in a dose dependent manner. Eleven patients (20%) developed ADR, the most common of which were arrhythmias. The SDC of patients with ADR was (2.55±1.59) ng/mL, which was significantly higher than that of the non-ADR group (0.93±0.63 ng/mL) (P<0.000 1). The SDC in the patients with increased serum creatinine was higher than that in the normal creatinine group, and patients with severe renal impairment demonstrated significantly higher concentration of digoxin than that in patients with normal renal function (P<0.05). The effect of concomitant administration of other drugs on the SDCof digoxin was not observed. CONCLUSION: The SDC varies greatly among individuals, and is associated with dosage and renal function. The higher the concentration of digoxin in serum, the higher the incidence of ADR. Therefore, monitoring the SDC of digoxin should be strengthened, so as to improve the level of individual treatment.