| ePocrates Online Premium* | http://www.epocrates.com | Uses natural medicine database |
| HerbMed by the Alternative Medicine Foundation† | http://www.herbmed.org | Directly linked to PubMed |
| Medscape* drug interaction checker | http://www.medscape.com/druginfo/druginterchecker | Searches prescription and over-the-counter drugs, and dietary supplements |
| Medwatch, the FDA Safety Information and Adverse Event Reporting Program | http://www.fda.gov/medwatch | Online form to report all suspected drug–dietary supplement interaction |
| NCCAM | http://nccam.nih.gov | NIH-sponsored center, has useful patient information |
| Natural Medicines Comprehensive Database* | http://www.naturaldatabase.com | Thorough and up-to-date information; has a drug–supplement interaction program |
| Natural standard | http://www.naturalstandard.com | Thorough monographs, including herb-drug interactions |
| Tatro, DS. Drug Interaction Facts. St. Louis, Mo.: Facts and Comparisons, 2006 | http://www.factsandcomparisons.com | Helpful textbook on interactions for medications as well as dietary supplements |