In Health Watch:Millions of Americans use herbal remedies but a new study find they can pose a risk to some heart patients.Researchers say some supplements can reduce the effectiveness of certain heart medications.Janet Choi has more.Dale Burg has been trying to manage her high blood pressure for nearly a decade.Dale says, "I take 3 or 4 medications every day."Burg sticks to her prescriptions.. but not all heart patients do.More than 15 million Americans use herbal remedies or high dose vitamins.. and a new study finds those supplements can be dangerous when taken on top of heart medication.. especially in the elderly.Dr. Nieca Goldberg says, 'I think that one of the most common misconceptions that people have about herbal remedies is that they are natural and therefore they are good for you. And that couldn't be further from the truth.The study found the herbal remedy St. John's Wort.. which some take to treat anxiety.. can reduce the effectiveness of certain heart drugs.While Ginkgo biloba and Garlic supplements ... can increase bleeding risk..when taken with blood thinners.. and even aspirin in some cases..One of the biggest concerns in this study is that here in the exam room, patients usually don't tell their doctors if they are taking any supplements.. and doctors may not ask.Dr. Goldberg says, 'Not telling your doctor is probably the most dangerous thing you can do for yourself.The supplement industry also says it is important people taking herbal remedies speak with their doctors.Supplements are not subject to same regulation as traditional medications...Dale Burg says, 'I try to be very careful that i don't take anything that might interact.'And it's not just heart patients who should be concerned.Dale says, 'You can't diagnose for yourself just because it's in the store and available without a prescription.Anyone taking prescription medication should ask their doctor if their supplements could be harmful.