BACKGROUND: There is limited information on complementary medicine (CM) use among older adults living in residential aged care facilities (RACFs). This study aimed to determine the prevalence and predictors of CM use and to examine differences in CM use by facility for residents of RACFs. METHODS: We conducted a retrospective study using routinely collected electronic data about permanent residents aged ≥ 65 years in December 2021 from 23 RACFs in Sydney. The prevalence of CM product use was estimated, and modelling was used to determine factors associated with CM use. Funnel plots visualised differences in prevalence of CM use between facilities. RESULTS: A total of 1,873 residents were included in the analysis with 78.4% (95% CI: 76.5-80.3) using at least one CM product and 41.2% (95% CI: 39-43.4) using 2 or more CMs. The most frequently used CM products were vitamin D (61.4%), magnesium (18.0%) and calcium (13.1%). Certain diagnoses were associated with both the likelihood of using a CM as well as the number of CMs used. For example, individuals with fractures were more likely to use ≥ 2 CMs (OR 1.29
95% CI 1.05-1.58), as were those with an endocrine disorder. Residents with circulatory conditions and dementia were less likely to use ≥ 2 CMs. The prevalence of residents using at least one CMs ranged from 54 to 88% between facilities. CONCLUSIONS: The prevalence of CM use is high in RACFs. Research to investigate the appropriateness of CM use to ensure their safe and effective use in RACFs is needed.