Potential Interactions Between Warfarin and Herbs

Many common herbs and nutritional supplements, if taken with the prescription drug warfarin (Coumadin), may change the effectiveness of the drug and potentially result in deadly adverse effects. Warfarin has a narrow therapeutic index (there is a small difference between the minimum effective and minimum toxic doses). Some herbs and supplements contain substances that may raise the risk of bleeding complications, while others work against warfarin, making people more prone to develop blood clots or stroke.

If you are taking the drug or any other prescription medication, it is crucial that you talk with your doctor about any herbal or nutritional supplement (including food powders, oils, teas, or juices), you are taking or are considering taking. Here are some of the herbs and supplements that may interact with warfarin. 

• Alfalfa - contains vitamin K
• Alpha-linolenic acid (ALA) - e.g. flaxseed oil, pumpkin seed oil
• Boswellia (Boswellia serrata)
• Camellia sinensis - e.g. black tea, green tea
• Chamomile (Matricaria chamomilla)
• Cocoa
• Coenzyme Q10
• Cranberry
• Danshen (Salvia miltiorrhiza) - may decrease platelet aggregation and increase the bleeding risk.
• DHA (docosahexaenoic acid)/ EPA (eicosapentaenoic acid)
• Dong quai (Angelica sinensis) - may inhibit platelet aggregation and increase the risk of bleeding.
• Feverfew (Tanacetum parthenium)
• Fish oil / omega-3 fatty acids
• Gamma-linolenic acid (GLA) - e.g. evening primrose oil. Could have anticoagulant effects.
• Garlic (Allium sativum)
• Ginger (Zingiber officinale)
• Ginkgo biloba
• Ginseng (all types)
• Glucosamine - may increase the anticoagulant effects of warfarin and increase the risk of bleeding, alone or in combination with chondroitin.
• Goji berry / Chinese wolfberry (Lycium barbarum)
• Goldenseal
• Kava kava
• Licorice 
• Milk thistle
• N-acetyl glucosamine
• Policosanol - may inhibit platelet aggregation
• Psyllium
• Red yeast rice
• Saw palmetto (Serenoa repens)
• St. John's wort - may decrease the therapeutic effects of warfarin.
• Vitamin E
• Vitamin K - may reduce the anticoagulant effect of warfarin.
• White willow bark - may increase the risk of bleeding.
• Topical wintergreen oil products (due to systemic absorption of methyl salicylate in wintergreen gels, lotions, cream, ointment, and spray.
• Turmeric/curcumin
• Wormwood (Artemisia absinthium)
• Yarrow

Other herbs and supplements that may interact with warfarin:

Acerola, acetyl-L-carnitine, activated charcoal, African wild potato, agar, agrimony, alchemilla, alder buckthorn, allspice, aloe, American chestnut, American elder, Andrographis, aniseed, antioxidants, apitherapy, arnica, asafoetida, ascorbigen, avocado

Baikal skullcap, barley, basil, bee pollen, berberine, bilberry, bishops weed, bistort, bitter orange, black currant, black mulberry, black and white pepper, black root, black seed, bladderwrack, blond psyllium, blue flag, blue-green algae, bogbean, boldo, borage, broccoli, bromelain, buchu, bupleurum, burdock, butternut

Cabbage, caffeine, capsicum, carrageenan, cascara, cassia, cat's claw, celery, celery seed, chanca piedra, Chinese prickly ash, chitosan, chlorella, chrysin, cinchona, clove, cod liver oil, codonopsis, coffee, cola nut, coleus, colocynth, coltsfoot, conjugated linoleic acid, cordyceps, corn silk, cranberry, cumin

Dandelion, deer tongue, devil's claw, DHA, DHEA, dehydroepiandrosterone, DMSO

Eastern hemlock, echinacea, eucalyptus, European barberry, European buckthorn, European chestnut, European mandrake, evodia

Fennel, fenugreek, flaxseed, flaxseed oil, fo-ti, forsythia, fulvic acid

Gamboge, gamma linolenic acid, german chamomile, glucomannan, goat's rue, goji, goldenseal, goldthread, gossypol, grape, great plantain, greater bindweed, green coffee, guarana, guggul, 

Hesperidin, higenamine, holy basil, honey, honeysuckle, hops, horny goat weed, horse chestnut, horseradish, hu zhang

Iceland moss, Indian frankincense, Indian gooseberry, indole-3-carbinol, inositol nicotinate, IP-6, ipriflavone

Jalap, Japanese apricot, jiaogulan, 

Karaya gum, kava, kinetin, kiwi, krill oil, kudzu

L-arginine, L-carnitine, lime, limonene

Magnesium, magnolia, maitake mushroom, mangosteen, manna, marijuana, marjoram, marshmallow, meadowsweet, melatonin, melilot, mesoglycan, methoxylated flavones, Mexican scammony root, moringa, Mormon tea, myrrh

N-acetyl cysteine, nattokinase, noni, nopal (cactus), nutmeg

Olive, onion, oolong tea, oregano, Oregon grape

Palm oil, pantethine, papain, papaya, passionflower, pau d'arco, pectin, peony, peppermint, Phellodendron, pomegranate, poplar, prickly ash, propionyl-L-carnitine, propolis, pue-erh tea, purple nut sedge, pycnogenol

Quassia, quercetin, quillaia, quince, quinidine

Raspberry ketone, red clover, reishi mushroom, resveratrol, rhatany, Rhodiola, rhubarb, rice bran, rose hip, rosemary, royal jelly 

Safflower, sage, saw palmetto, schisandra, sea buckthorn, selenium, senna, serrapeptase, Siberian ginseng, slippery elm, smartweed, soy, spinach, stinging nettle, strawberry, sulforaphane, summer savory, swallowroot, sweet clover, sweet vernal grass, sweet woodruff

Tannic acid, tarragon, thyme, tiratricol, tonka beans, tragacanth, tree turmeric

Umckaloabo

Valerian, vanadium, vinpocetine, vitamin A, vitamin C

Water avens, watercress, wild carrot, wild cherry, wild lettuce, willow

Yarrow, yellow dock, yerba mate, Yohimbe

This is not a complete list and it is essential that you speak with your physician before starting any form of alternative medicine or changing your prescribed treatment regimen. Keep in mind that the side effects and potential drug interactions for many herbs and supplements are poorly understood.