Researchers from the University of Chicago report in the July 6, 2004, issue of the Annals of Internal Medicine that ginseng, one of the best selling herbal supplements in the United States, interferes with warfarin, a drug commonly used to prevent blood clots.
The researchers encourage anyone who takes both ginseng and warfarin, also known as Coumadin®, to notify his or her doctor and urged doctors to ask patients on warfarin if they are taking ginseng.