The use of Complementary and Alternative Medicine (CAM) is increasingly popular in places like North America and Europe where western medicine is primarily practiced. People are consuming herbal and dietary supplements along with western medications simultaneously. Sometimes, supplements and drugs react with one another via antagonistic or potentiation actions of the drug or supplement resulting in an adverse event. Unfortunately, it is not easy to study drug-supplement interactions without a standard terminology to describe herbal and dietary supplements. This pilot study investigated coverage of supplement databases to one another as well as coverage by the Unified Medical Language System (UMLS) and RxNorm for supplement terms. We found that none of the supplement databases completely covers supplement terms. UMLS, MeSH, SNOMED CT, RxNorm and NDF-RT cover 54%, 40%, 32%, 22% and 14% of supplement concepts, respectively. NDF-RT provides some value for grouping supplements into drug classes. Enhancing our understanding of the gap between the traditional biomedical terminology systems and supplement terms could lead to the development of a comprehensive terminology resources for supplements, and other secondary uses such as better detection and extraction of drug-supplement interactions.