This article is for informational purposes only and does not replace medical advice. Consult your doctor or pharmacist before starting, stopping, or changing any supplement while on blood thinners.
Several common supplements increase bleeding risk when combined with blood thinners like warfarin, Eliquis, or Xarelto. The biggest ones to watch: fish oil at high doses, vitamin E above 400 IU, ginkgo biloba, garlic supplements, turmeric/curcumin, and St. John's Wort. Some supplements are perfectly safe. The key is knowing which category yours falls into before you start taking them together.
Why blood thinners and supplements interact
Blood thinners work by slowing your body's clotting process. Warfarin blocks vitamin K, which your body needs to form clots. Newer blood thinners like Eliquis (apixaban) and Xarelto (rivaroxaban) inhibit specific clotting factors directly. Plavix (clopidogrel) prevents platelets from sticking together.
Any supplement that also thins the blood, interferes with clotting factors, or changes how your body processes these drugs can tip the balance. The result: either too much blood thinning (bleeding risk) or too little (clotting risk).
This is not a "maybe it matters" situation. Supplement-blood thinner interactions send people to the emergency room. The National Institutes of Health and the NIH Office of Dietary Supplements both flag supplement-drug interactions as a serious concern.
Supplements to avoid or use with extreme caution
These supplements have documented interactions with blood thinners. Either avoid them entirely or use only under direct medical supervision.
Fish oil / omega-3 fatty acids
Fish oil has its own mild blood-thinning effect. At low doses (1,000 mg or less), the added risk is small. At higher doses (3,000+ mg), the antiplatelet effect becomes significant. Combined with warfarin or Eliquis, this stacks two blood-thinning mechanisms. The NIH Office of Dietary Supplements notes that high-dose fish oil (2 g or more EPA/DHA daily) can reduce platelet aggregation and prolong bleeding time. If your doctor has approved fish oil, stick to the lowest effective dose and report any unusual bruising.
For timing details on fish oil specifically, see our guide on fish oil: morning or night.
Vitamin E (above 400 IU)
Vitamin E inhibits platelet aggregation. At standard multivitamin doses (30 IU), this is not a concern. At supplemental doses above 400 IU, the antiplatelet effect is strong enough to add meaningful bleeding risk on top of your blood thinner. A meta-analysis in the Annals of Internal Medicine also linked high-dose vitamin E to increased all-cause mortality. Unless your doctor has specifically prescribed high-dose vitamin E, keep it under 400 IU.
Ginkgo biloba
Ginkgo is one of the most well-documented supplement risks for blood thinner users. It inhibits platelet-activating factor (PAF), which means it directly interferes with blood clotting. Case reports have linked ginkgo to spontaneous bleeding events, including subdural hematoma, in patients on anticoagulants. Avoid ginkgo entirely while on any blood thinner.
Garlic supplements (concentrated)
Regular food-quantity garlic in cooking is fine. Concentrated garlic supplements (allicin extract, aged garlic) are a different story. They inhibit platelet aggregation and may increase the activity of blood thinners. The National Center for Complementary and Integrative Health specifically warns about garlic supplement interactions with anticoagulants.
Turmeric / curcumin (high-dose supplements)
Curcumin has antiplatelet and anticoagulant properties at supplemental doses. A study in Thrombosis Research showed curcumin inhibits platelet aggregation. Turmeric in food is generally fine. High-dose curcumin capsules (500+ mg of concentrated curcumin) combined with blood thinners create additive bleeding risk.
Other supplements to avoid
- Ginger supplements (concentrated capsules, not kitchen ginger): mild antiplatelet effect
- Dong quai: contains coumarins that can potentiate warfarin
- Feverfew: inhibits platelet aggregation
- St. John's Wort: does not increase bleeding directly, but it induces liver enzymes that can dramatically reduce the effectiveness of warfarin, Eliquis, and Xarelto. This is equally dangerous in the opposite direction: your blood thinner may stop working.
Pillo includes a Drug-Drug Interaction Checker that lets you plug in your blood thinner and each supplement to see flagged interactions before you buy anything new.
The warfarin-specific vitamin K rule
If you take warfarin, vitamin K deserves its own section because the interaction is unique and widely misunderstood.
You do not need to avoid vitamin K. You need to keep your vitamin K intake consistent from day to day.
Warfarin works by blocking vitamin K's role in the clotting process. Your doctor sets your warfarin dose based on your typical vitamin K intake. If you suddenly eat a large salad or start a vitamin K supplement, your INR drops and your blood thickens. If you suddenly stop eating greens, your INR rises and your bleeding risk increases.
The fix: eat roughly the same amount of vitamin K-rich foods each week. Do not start or stop vitamin K supplements without telling your doctor. Do not go on a kale binge one week and then eat no greens the next.
This rule does not apply to Eliquis, Xarelto, or Plavix. Those drugs do not interact with vitamin K.
For more on vitamin K interactions, see our guide on vitamin D and K2 together, which covers when K2 supplementation makes sense and when it does not.
CoQ10 and warfarin
CoQ10 (ubiquinone) has a chemical structure similar to vitamin K2. Several case reports suggest it can reduce warfarin's effectiveness, lowering your INR. If you take warfarin and want to add CoQ10, tell your doctor so they can monitor your INR more closely during the transition. This interaction is less of a concern with Eliquis or Xarelto.
Supplements that are generally safe with blood thinners
Not everything is off-limits. These supplements have no significant known interactions with common blood thinners:
| Supplement | Notes |
|---|---|
| Vitamin D | Safe at standard doses. No clotting interaction. See can you take too much vitamin D for dosing guidance. |
| Calcium | Safe. No blood thinner interaction. |
| Magnesium | Safe at normal doses. Very high doses may have a mild additive effect. See best time to take magnesium. |
| B vitamins (B6, B12, folate) | Safe. May help lower homocysteine, which is good for cardiovascular health. |
| Iron | Safe. No clotting interaction. Timing matters for absorption though. See iron supplement timing. |
| Probiotics | Safe. No known blood thinner interaction. |
| Vitamin C (under 1,000 mg) | Safe at moderate doses. Very high doses (2,000+ mg) may theoretically affect warfarin, but standard supplementation is fine. |
Quick reference: the full interaction chart
| Supplement | Risk level | Interaction type | Blood thinners affected |
|---|---|---|---|
| Fish oil (high dose) | Moderate | Adds blood-thinning effect | All |
| Vitamin E (>400 IU) | Moderate to high | Inhibits platelet aggregation | All |
| Ginkgo biloba | High | Blocks platelet-activating factor | All |
| Garlic supplements | Moderate | Inhibits platelet aggregation | All |
| Turmeric/curcumin | Moderate | Antiplatelet + anticoagulant | All |
| Ginger supplements | Low to moderate | Mild antiplatelet effect | All |
| Dong quai | High (warfarin) | Contains coumarins | Warfarin especially |
| Feverfew | Moderate | Inhibits platelet aggregation | All |
| St. John's Wort | High | Reduces drug effectiveness | Warfarin, Eliquis, Xarelto |
| CoQ10 | Moderate (warfarin) | May reduce warfarin effect | Warfarin |
| Vitamin K | Context-dependent | Consistency matters | Warfarin only |
| Vitamin D, calcium, magnesium, B vitamins, iron | Low | No significant interaction | None |
If you are managing blood thinners plus supplements, setting separate timed reminders helps you keep everything spaced correctly. Pillo's persistent alarm keeps going until you confirm each dose, which prevents the kind of "did I already take that?" confusion that gets risky with anticoagulants.
What to do before adding any supplement
- Tell your doctor or pharmacist. This is not optional with blood thinners. Bring the bottle or show them the exact product.
- Check the interaction. Ask your pharmacist to screen your supplement against your blood thinner before purchasing.
- Start low. If your doctor approves a supplement, begin at the lowest dose and monitor for bruising, bleeding gums, or prolonged cuts.
- Watch your INR (warfarin users). Any new supplement warrants an INR check 1 to 2 weeks after starting.
- Do not stop supplements suddenly. If you have been taking vitamin K or another supplement regularly, stopping abruptly can shift your clotting balance just as much as starting something new.
FAQ
Can I take fish oil with Eliquis?
Low-dose fish oil (1,000 mg or less) is considered low risk with Eliquis by most clinicians, but it does have a mild additive blood-thinning effect. Tell your doctor before combining them. Higher doses (3,000+ mg) are more concerning due to increased antiplatelet activity.
Is turmeric safe with warfarin?
Turmeric in food (curries, golden milk with a pinch of turmeric) is generally fine. Concentrated curcumin supplements at 500+ mg are not recommended without medical supervision. Curcumin has documented antiplatelet and anticoagulant effects that add to warfarin's activity.
Do I need to avoid all vitamin K on warfarin?
No. The goal is consistency, not avoidance. Eat roughly the same amount of vitamin K each week. Sudden increases or decreases in vitamin K intake will affect your INR and make your warfarin dose unreliable. Do not start or stop K supplements without talking to your doctor.
Can I take magnesium with blood thinners?
Yes, magnesium is safe with blood thinners at standard supplemental doses (200 to 400 mg). At very high doses, magnesium may have a mild additive blood-thinning effect, but this is not clinically significant for most people. See our full guide on magnesium timing.
What about a daily multivitamin?
Most standard multivitamins are safe with blood thinners. The vitamin K content is usually small and consistent (50 to 80 mcg), which is fine for warfarin users as long as you take the same multivitamin daily. Check the label for vitamin E content and make sure it is under 400 IU. Avoid multivitamins with added herbal blends that may include ginkgo, garlic, or ginger extracts.
Should I stop all supplements before surgery?
Most surgeons ask patients to stop supplements with blood-thinning effects (fish oil, vitamin E, ginkgo, garlic, turmeric) 7 to 14 days before surgery. Your blood thinner management around surgery is a separate decision your doctor will handle. Always provide a complete list of everything you take, including supplements.
Related guides:
- Supplement timing chart: when to take each vitamin
- Which vitamins should not be taken together
- Fish oil: morning or night?
- Best time to take magnesium
- Can you take too much vitamin D?
- Missed dose of Eliquis
- Missed dose of warfarin
- Missed dose of Xarelto
This article is for informational purposes only. It is not medical advice. Consult your doctor or pharmacist before starting, stopping, or changing any supplement while taking blood thinners.
