Objective: The purpose of this study was to investigate the level of safety on liver functions when Korean herbal medicine was taken internally. Method: 101 inpatients who took Korean herbal medicine were enrolled and liver function test (aspartic aminotransferase, alanine aminotransferase, alkaline phosphatase, total bilirubin, gamma glutamyltranspeptidase, albumin, lactate dehydrogenase) was performed on admission and 1 month later. Results: In 101 patients, alkaline phosphatase and gamma glutamyltranspeptidase decreased significantly compared with the value taken on admission (p<0.05) but aspartic aminotransferase, alanine aminotransferase, total bilirubin, albumin, and lactate dehydrogenase were not significantly changed (p>0.05). In the patients who took Scutellaria baicalensis (n=34), alkaline phosphatase decreased and albumin increased significantly (p<0.05). Among the patients who took Atractylodes macrocephala (n=29), alkaline phosphatase decreased significantly (p<0.05). In the patients who took Glycyrrhiza uralensis or Paeonia lactiflora, liver function parameters were not significantly changed (p>0.05). On admission 11 patients had abnormal liver function and 2 patients had liver injury while 7 patients had abnormal liver function and 2 patients showed liver injury 1 month later. Conclusions: This study suggests that prescribed Korean herbal medicine does not injure liver function.