You probably know someone on a blood thinner. Maybe a parent after a heart valve replacement, maybe a friend after a clot in the leg. What fewer people know is that the small bottles on the kitchen counter can quietly throw the whole thing off.
More than eight million people in the United States currently take a blood-thinning drug, according to the National Blood Clot Alliance. The best-known is warfarin, sold for decades as Coumadin.
The problem is that many popular supplements interact with warfarin in two opposite ways. Some add to the drug's blood-thinning effect and raise the risk of bleeding. Others cancel the drug out and raise the risk of a clot.
Here are seven supplements that keep showing up on authority warning lists, and what each one actually does to the medication.
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The two that most people have in the cupboard
Fish oil. Omega-3 capsules have their own mild blood-thinning effect. At high doses they can push bleeding time up when added on top of warfarin. The anticoagulation clinic at UC San Diego Health lists fish oil as a supplement that increases bleeding risk.
Vitamin E. At higher doses, vitamin E raises the INR. That is the lab number doctors use to track how thin the blood is. A higher INR means a greater chance of bleeding. The UC San Diego list flags vitamin E for exactly that reason.
Herbal supplements that amplify bleeding
Garlic supplements. Concentrated garlic pills are not the same as cooking with a clove. The National Center for Complementary and Integrative Health says garlic supplements may increase the risk of bleeding. It advises people who take them to tell their health care providers.
Ginkgo biloba. Marketed for memory and circulation, ginkgo has an antiplatelet effect of its own. The NCCIH says ginkgo may increase the risk of bleeding in people taking anticoagulant drugs such as warfarin.
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Turmeric and curcumin. The active compound in turmeric can inhibit platelet aggregation. That is why high-dose curcumin extracts, not kitchen seasoning, are the concern. The UC San Diego anticoagulation list flags turmeric as a bleeding-risk interaction with warfarin.
Two that work the other way
St. John's wort. This herb is widely used for low mood, but it speeds up the body's breakdown of many drugs. The NCCIH warns that St. John's wort can weaken the effects of warfarin, which means less protection against a clot.
Coenzyme Q10 (CoQ10). CoQ10 is structurally similar to vitamin K, the vitamin that warfarin blocks. That is why it can nudge the drug's effect in either direction.
The patient drug resource MedlinePlus, run by the National Library of Medicine, lists CoQ10 as a supplement that can interact with warfarin. Other names on the list include echinacea, ginseng and goldenseal.
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What to actually do about it
The bigger risk is often not the supplement itself but the silence around it. Patients routinely tell their doctor every prescription in their medicine cabinet. Then they forget to mention the fish oil, the turmeric or the multivitamin on the kitchen counter.
Tell your doctor and pharmacist about every supplement you take, including the ones you consider harmless, before starting warfarin and before adding anything new.
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This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.