Background: Serum drug concentration (SDC) is an important parameter used in drug efficacy and treatment follow-up. 
 Aim: This study aimed to evaluate SDC and the influencing factors for carbamazepine, phenytoin, phenobarbital, lithium and digoxin.
 Materials and Methods: This is a cross-sectional study, evaluating the outpatients’ and inpatients’ SDC data treated at Research and Application Hospital of Afyonkarahisar Health Sciences University between January 1, 2012 and December 31, 2019, and having SDC data. The relations between dependent and independent variables was evaluated with chi-square analysis and Students’ T-test. P