As the clinical application and consumption of dietary supplements has grown, their side effects and possible interactions with prescribed medications has become a serious issue. Information extraction of dietary supplement related information is a critical need to support dietary supplement research. However, there currently is not an existing terminology for dietary supplements, placing a barrier for informatics research in this field. The terms related to dietary supplement ingredients should be collected and normalized before a terminology can be established to facilitate convenient search on safety information and control possible adverse effects of dietary supplements. In this study, the Dietary Supplement Label Database (DSLD) was chosen as the data source from which the ingredient information was extracted and normalized. The distribution based on the product type and the ingredient type of the dietary supplements were analyzed. The ingredient terms were then mapped to the existing terminologies, including UMLS, RxNorm and NDF-RT by using MetaMap and RxMix. The large gap between existing terminologies and ingredients were found: only 14.67%, 19.65%, and 12.88% of ingredient terms were covered by UMLS, RxNorm and NDF-RT, respectively.