10 Supplements That Don’t Mix Well With Blood Thinners

Certain herbal and dietary supplements can offer health benefits, but some can interact with medications, such as blood thinners. Vitamin E, ginkgo, garlic, ginger, and omega-3s are among those that can increase your risk of bleeding or other side effects.

1. Vitamin E

High doses of vitamin E supplements can reduce the body's ability to form blood clots.

It can do this by interfering with the metabolism of vitamin K, which is essential for activating several blood-clotting factors, or proteins in the blood that helps form blood clots to stop bleeding. Vitamin E also reduces platelet aggregation (where platelets clump together to form a clot).

Excessive intake of supplements can increase the risk of bleeding, including a rare but serious risk of hemorrhagic stroke (bleeding in the brain). This risk is highest in people who are already taking anticoagulant (blood thinner) medications like warfarin or antiplatelet drugs like aspirin or Plavix (clopidogrel).

2. Omega-3

Omega-3 supplements are often used to improve cholesterol levels and heart health.

Omega-3 fatty acid supplements, particularly those containing the fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil, can prevent platelets from clumping together and forming clots. This can reduce blood clotting, prolonging the time it takes to stop bleeding.

However, the risk of clinically significant blood thinning is generally low for most people taking standard doses.

3. Grapefruit Seed Extract

Grapefruit seed extract is commonly used for its antimicrobial properties. However, it can have a significant and potentially dangerous interaction with certain blood-thinning medications.

Grapefruit contains chemicals that can interfere with the enzymes responsible for breaking down drugs in the body. When taken with blood thinners, this can cause increased levels of the drug in the body, thereby further enhancing its effects. This can lead to serious side effects like bleeding, bruising, or hemorrhage (excessive bleeding).

4. Coenzyme Q10

Coenzyme Q10 (CoQ10) is an antioxidant supplement. It can also interact with blood-thinning medications, decreasing their effectiveness.

CoQ10 has a chemical structure similar to that of vitamin K, which is essential for the production of several blood-clotting factors. Due to its similarity, CoQ10 may interact with enzymes, potentially counteracting the effect of warfarin. This can hamper its ability to reduce blood clot formation, resulting in a risk of a dangerous clot (thrombosis).

There is very little to no clinical data on the interaction between CoQ10 and other blood thinners. 

5. Don Quai

Dong quai is a traditional Chinese medicine with mild sedative, analgesic, antispasmodic, anti-inflammatory, and antiplatelet/anticoagulant effects.

It can prolong the time it takes for your blood to clot and worsen bleeding. Because of these effects, dong quai can cause excessive bleeding with warfarin.

More research is required, but people taking this herb in combination with blood-thinning medications should be more cautious.

6. Ginseng

Ginseng is an herbal supplement with antioxidant benefits. It is also sometimes consumed as a tea. Some use it to improve fatigue and boost brain and immune health.

Ginseng can interact with blood thinners by increasing the risk of bleeding. It may slow blood clotting and prevent platelets from clumping together to form clots.

When combined with blood-thinning medication like warfarin, it can increase the effects and raise the risk of bleeding.

7. St. John's Wort

St. John's Wort is another traditional herbal Chinese medicine. It's often used to help with symptoms of depression, though there's not enough evidence to recommend it.

St. John's Wort can significantly speed up the metabolism of many blood thinners, reducing their concentration and effectiveness. It should not be used with warfarin as it may reduce the effects of the drug.

8. Vitamin K

Vitamin K is known as the natural vitamin that promotes blood clotting. It makes specific proteins in the liver that cause blood to clot. These proteins are called clotting factors.

Taking vitamin K or supplements containing vitamin K can increase the clotting factors.

Vitamin K or foods containing vitamin K can reduce the effectiveness of blood thinners, such as warfarin, due to increased clotting factors.

Avoid taking vitamin K supplements and be mindful of consuming vitamin K-rich foods while taking a blood-thinning medication. Foods rich in vitamin K include leafy green vegetables such as kale, spinach, and Brussels sprouts.

9. Ginger

Ginger dietary supplements are sometimes used for medicinal purposes, including nausea, osteoarthritis, menstrual cramps, and other conditions.

Although further research is needed, ginger may help prevent or slow down blood clotting. When taken in large amounts or concentrated supplements, it may enhance the effect of blood thinners such as warfarin, which can increase the risk of bleeding or bruising.

Although there has been no direct advisory, the Food and Drug Administration (FDA) advises healthcare providers to exercise caution in people who are on warfarin and also use ginger, garlic, and other dietary and herbal supplements.

10. Garlic

Garlic offers several heart health benefits, including blood pressure regulation, cholesterol management, and weight control, among others. Garlic supplements can interfere with your body's blood-clotting abilities.

The findings of various studies suggest that garlic can decrease the antiplatelet and anticoagulant effects of aspirin and other blood-thinning medications, particularly warfarin.

When taking blood-thinning medicines, it is better to avoid high doses of garlic supplements to prevent an increased risk of bleeding.

Talk to your healthcare provider about how much garlic is safe to consume while on blood thinners.

Other Supplements

Some other herbs may also not mix well with blood thinners, but the evidence is not strong.

These include:

• Aloe

• Cranberry

• Feverfew

• Meadowsweet

• Turmeric

• White willow

• Chamomile tea

• Green tea

• Oregano tea