Coumadin is a medication called a blood thinner, although the correct term is anti-coagulant. This medication is used to help prevent blood clots from forming and is sometimes prescribed after a stroke or heart attack. Coumadin can interact with a number of nutritional supplements. The term supplement may be used for vitamins, minerals or herbal preparations. Compounds in each of these categories may cause problems with Coumadin.
Vitamins
When you are taking Coumadin, the vitamin you should be most concerned about is vitamin K. Found in leafy green vegetables such as kale, collard greens and spinach as well as nutritional supplements, vitamin K can counteract the effect of Coumadin and make it less effective. Vitamin E may also interact with Coumadin, but it increases the risk of bleeding. The Linus Pauling Institute says that vitamin C may block the action of Coumadin and recommends limiting intake to 1 g a day.
Minerals
The website Vitamin Lore reports that several minerals -- iron, magnesium and zinc -- may interact with Coumadin by binding with the medication. This effect may decrease the absorption and activity of Coumadin. Vitamin Lore recommends that if you take Coumadin, you should take these mineral supplements at least two hours before or after your Coumadin dose.
Herbs and Other Supplements
The Cleveland Clinic says you should not take chamomile, tonka beans, sweet woodruff or sweet clover, whether in herbal tea or supplement form. Any of these may affect the action of Coumadin, either by making it less effective or by increasing the risk of bleeding. In addition, the Cleveland Clinic says you should not start to take any of the following without checking with your doctor: any vitamin supplement that provides more than 100 percent of the recommended daily intake for vitamins A, E and C; fish oil supplements; garlic oil supplements; ginger supplements; and onion extract pills.
Foods as Supplements
Many substances that are used both as foods and also in supplement form can interact with Coumadin. According to the Cleveland Clinic, foods used in cooking or as a seasoning such as celery, clove, garlic, ginger and parsley, are usually safe. However, none of these should be used as a supplement if you are taking Coumadin. Other prohibited food and supplement items include alfalfa or alfalfa sprouts, cranberry, fenugreek, green tea and licorice. Non-food supplements such as devil's claw, echinacea, ginkgo biloba and St. John's wort are not safe when you are taking Coumadin.
Considerations and Warnings
The side effects from Coumadin can be dangerous, and using some supplements may increase the risk of bleeding or prevent the medication from working correctly. If your health-care professional prescribes Coumadin and you are taking supplements, let him know. If you take Coumadin, don't start supplements without consulting a health-care professional.
References
- National Institutes of Health; Important Information to Know When you are Taking Coumadin and Vitamin K; December 2003
- Drugs.com; Coumadin; December 2010
- Coumadin.com; Coumadin; 2009
- Linus Pauling Institute; Vitamin C; Jane Higdon, Ph.D, et al.; November 2009
- VitaminLore.com; Warfarin; 2002
- Cleveland Clinic; Drugs and Supplements: Anticoagulant Medication Warfarin (Coumadin); August 2007
