Objective: Laboratory tests are commonly used in Korean medicine (KM) clinics to monitor the safety of herbal medicine (HM). Although the incidence of herb-induced liver injury (HILI) in Republic of Korea has been reported, there is a lack of data from KM clinics, which account for over 90% of KM institutions. This absence is due to the lack of a systematic pharmacovigilance system for HMs. To partially understand this issue, this study investigated changes in liver function test (LFT) and renal function test (RFT) after HM prescriptions in primary settings.
Methods: This retrospective analysis utilized laboratory test results, including complete blood count, LFT and RFT, collected from 238 KM clinics across the Republic of Korea. The study population comprised patients who underwent laboratory testing before and after HM treatment between March 2020 and November 2021. We compared laboratory test results using paired t-tests or Wilcoxon signed-rank tests. Subgroup analyses were conducted by sex and elapsed time between tests. The McNemar test was used to compare the proportions of cases with abnormal LFT and RFT levels according to lifestyle habits and comorbidities. Additionally, the incidence of liver injury was estimated by identifying cases with aspartate aminotransferase (AST) or alanine aminotransferase (ALT) levels exceeding five times the upper limit of normal after HM prescription.
Results: A total of 2791 cases were included in the analysis. The levels of AST and ALT decreased significantly after HM prescription (P < 0.0001). This result was consistent in subgroups stratified by sex and for test intervals of within 30 and 60 days (P < 0.05). The proportion of cases with abnormal AST and ALT levels significantly decreased after HM prescription (P < 0.001). Out of 2791 cases, only 2 (0.07%) were identified as having liver injury after HM prescription, but causality was not confirmed.
Conclusion:The findings suggest that the use of HM in KM clinics in Republic of Korea is generally safe. While a small number of HMs may be associated with liver injury, causality remains uncertain. Establishing a national pharmacovigilance system is crucial for accurately monitoring the incidence and risk factors of HILI. Please cite this article as: Cho E, Ko MM, Yang C, Kim S. Safety of herbal medicines in Korean medicine clinics in Republic of Korea: A nationwide retrospective longitudinal cohort study. J Integr Med. 2026; 24(2):192-200.

Key words: Adverse drug event, Drug-induced liver injury, Herbal medicine, Korean medicine, Pharmacovigilance