Vitamin and herbal supplements can have severe interactions with one‘s prescription medications. This is why people should list any such supplements along with their other medications when visiting the doctor, to be sure they don‘t pose a risk, says Michele Caliva, a nurse and the administrative director of the Upstate New York Poison Center. She notes the problems that are caused by some supplements, such as chamomile, St. John‘s wort, soy and ginkgo biloba, and she says there is sparse regulation of these supplements and often little or no research to support their health claims.