If you take Coumadin (generic name warfarin), you know that it can interact with a variety of other medications. But did you know that it can interact with herbs as well? Warfarin-herb interactions can be just as serious as any drug-drug interaction, resulting in an increased risk of hemorrhage, stroke or worse. For this reason, it is important that you consult your doctor before beginning any new supplement or vitamin preparation, while taking warfarin.

Let’s take a look at some of the more common herbal interactions. If you are taking any of these herbs, it is important that you do not quit them abruptly. It is possible that abruptly stopping the herb, in itself, could result in a change in your blood’s ability to clot and possible side effects. Instead, talk first to your doctor to see how you should proceed.

Herbs That Increase Your Bleeding Risk

Most warfarin-herb interactions result in an increased risk of bleeding. Several spices such as anise, licorice, celery, clove and ginger interact with warfarin in this way. Anise and licorice are licorice flavored herbs that claims to help with a variety of problems including stress and stomach upset. Ginger is also widely used for stomach upset. Celery claims to lower cholesterol. Clove is used for many ailments including stomach problems and inflammation. All of these herbs make the blood ‘thinner’ when taken with warfarin.

Speaking of inflammation, there are many herbs that are commonly used for inflammation that increase the risk of bleeding when taken with warfarin. Willow bark, chondroitin, Vitamin E and feverfew are a few of these herbs. Garlic, flaxseed and papaya, which are thought to help with heart health, also interact in this way.

Black cohosh, red clover and don quai are most often included in herbal menopausal preparations. They also increases the risk of bleeding when taken with warfarin. Echinacea and horseradish, which are meant to help with colds, also increase this risk.

Other herbs that are found in herbal relaxation preparations such as passion flower and chamomile have this same effect. On the other hand, there are herbs such as ginseng and ginko biloba that are meant to promote alertness that also interact in this way. Horse chestnut which is used for vein health, also in capable of the interaction.

Herbs That Increase the Risk of Clots

There are several herbs that counteract the ‘blood-thinning’ effects of warfarin. When taken with warfarin, these herbs may lessen warfarin’s effect and increase your risk of blood clots. These herbs include mistletoe, nettle, green tea, co-enzyme Q10 and dandelion. These herbs are used for a variety of health conditions and are found in a variety of supplements and teas.

What if I Don’t Take Herbal Supplements?

Some of you may be saying to yourself, ‘That’s ok, I don’t take any herbal supplements’.  If you fall into this group, beware that it is not always easy to know when we are taking herbs these days. If you check the label, you will find that these herbs appear in more vitamins, teas, beverages and foods than ever before.

 For example, many vitamin supplements now incorporate green tea into the formula. Many bottled fruit juices also contain herbs like ginseng, ginko biloba and green tea. To be sure, make sure you read food, beverage and supplement labels. If you see any of the herbs above, talk to your doctor before ingesting the food, beverage or supplement.

The Bottom Line

Drug-herb interactions should not be taken lightly. As mentioned above, they can result in interactions that are just as serious as drug-drug interactions. Many assume that because an herb is ‘natural’ that it must be safe. This is not the case. In fact, because herbs are not subject to stringent testing like prescription or over-the-counter drugs, there is much we don’t know about herbal interactions and side effects. Be cautious when taking herbal products, particularly if you are taking warfarin or other medications. When in doubt about an interaction, check with your doctor or pharmacist.