function. 3 They concluded that the number of prescribed medicines contributed to the worsening of renal function. Furthermore, Eppenga et al. (2015) presented a study protocol that analyzed fluctuations in renal function after discharge from the hospital and their effects on drug dosing. 4 The authors measured serum creatinine levels at three time-points (at discharge, and 14 days and 2 months after discharge) and examined the association between changes in renal function and the number of medications. The results of both of these studies suggested that polypharmacy was correlated with decreased renal function and with the exacerbation of renal dysfunction.Polypharmacy is considered a marker of multiple comorbidities, which could be the true cause of poor prognosis. However, it is unknown whether polypharmacy itself diminishes renal function or whether multiple comorbidities cause a decrease in renal function. In the present study, we found significant correlations between the number of medications administered and the serum creatinine level, BUN level, and eGFR. These results suggest a correlation between polypharmacy and renal function decline in older patients. Therefore, it is important for clinicians to consider the management of multiple diseases and health risks, particularly kidney function, associated with polypharmacy. Furthermore, even if a patient falls into the nonpolypharmacy group, it is undeniable that even a small number of drugs can decrease renal function. 6 Therefore, we believe that our report is important because it reminds clinicians of the serious impact of drug management on renal function in elderly patients.