Ginseng may reduce the blood concentrations and hypoprothrombinemic effect of warfarin. In one case report, use of Asian ginseng was associated with a reduction in INR in a patient who had been stabilized on warfarin for nine months.
Although it is usually perceived that taking herbal substances along with pharmaceutical products are harmless, it is still best to let the doctor know before taking any herbal medicines along with the prescribed drugs.