Blood Thinners and Supplements: What to Avoid

Avoid St. John's wort with any blood thinner: the apixaban and rivaroxaban labels say not to combine them, and it speeds up warfarin clearance^{1, 2, 3}. With warfarin, keep your vitamin K intake steady rather than cutting it out⁴.

Vitamin K is a warfarin issue only. The apixaban (Eliquis) and rivaroxaban (Xarelto) labels note that vitamin K is not expected to affect their anticoagulant activity, which is why it isn't used to reverse them^{1, 2}. For most other supplements the risk is additive bleeding, and the evidence is mostly case reports⁵. If you also take vitamin K2 with vitamin D, our guide to vitamin D3 and K2 supplements covers the combination.

Vitamin K works against warfarin but not against apixaban or rivaroxaban. Warfarin antagonizes vitamin K, which depletes the vitamin K-dependent clotting factors; sudden changes in vitamin K intake can raise or lower its effect⁴. For apixaban and rivaroxaban, both labels say vitamin K is not expected to change their anticoagulant activity, and neither lists dietary vitamin K as an interaction^{1, 2}.

What is the difference between vitamin K and warfarin?

They pull in opposite directions. Vitamin K1 lets the liver make working clotting factors, and warfarin blocks that step⁴. So more vitamin K means a lower INR (international normalized ratio, the clotting test warfarin is dosed by), and less means a higher one.

Should I take vitamin K if I'm on blood thinners?

Not on your own. A small daily dose has been tried as a deliberate way to steady warfarin, and the results are mixed:

• Positive trial: in 70 patients with unstable INR, 150 mcg of vitamin K daily for 6 months raised time in the target range by 28 percentage points vs 15 on placebo⁶.
• Null trial: a Canadian multicentre trial of 150 mcg daily for 6 months found no difference in time in range (65.1% vs 66%), though extreme INR swings fell⁷.
• Cochrane review: 2 trials with 100 participants gave insufficient data to show an overall benefit⁸.

That is a dosing decision for your anticoagulation clinic. On apixaban or rivaroxaban, vitamin K isn't expected to change the drug's effect^{1, 2}.

Can you take vitamin K2 (MK-7) on warfarin?

Treat it as a change in vitamin K intake that needs your prescriber's input. In 15 healthy adults on acenocoumarol, a drug that works like warfarin, 45 mcg of MK-7 a day cut the INR by about 40%⁹. Even 10 mcg and 20 mcg a day lowered INR to a clinically relevant degree in at least 40% and 60% of people⁹. The authors advised that MK-7 supplements be avoided on these drugs⁹.

A 2021 systematic review found 78 foods, herbs and supplements reported to interact with warfarin, across 149 articles¹⁰. Of these, 45 (57.7%) increased warfarin's effect and 23 (29.5%) decreased it¹⁰. Most of this evidence is weak: in an earlier review, 84% of interaction reports were of poor quality, and every one of the 31 serious bleeds was a single case report⁵.

Sorted by what the labels and controlled studies support^{11, 1, 2, 12}:

• Avoid with every blood thinner: St. John's wort. It lowers apixaban and rivaroxaban exposure, which the labels say raises the risk of stroke and clots^{1, 2}. With warfarin it raised clearance by about 29% and cut the INR response by 21%³.
• Avoid on warfarin unless your prescriber plans for it: vitamin K supplements, including vitamin K2 (MK-7)^{4, 9}.
• Caution, possible extra bleeding: ginkgo, garlic, ginger, cranberry, high-dose vitamin E, glucosamine and turmeric^{11, 10, 13, 14, 15}.
• Caution, clot-dissolving enzymes: a 2025 review notes that nattokinase use may be limited by bleeding risk or drug interactions¹⁶. Natto, the food, carries about 850 mcg of vitamin K2 per 3 oz, which matters on warfarin⁴.
• Caution, may change warfarin levels: echinacea, goldenseal and grapefruit juice are named on the warfarin label as interacting through liver enzymes¹¹.
• Caution, may weaken warfarin: CoQ10 and ginseng are named on the warfarin label, though controlled trials found no effect^{11, 17, 3}.
• No known interaction on the labels: magnesium, vitamin D and vitamin B12 aren't named on any of the three labels^{11, 1, 2}.

The newer drugs have far less research. A 2021 review concluded that people on any of these drugs should avoid products containing St. John's wort and take care with other food ingredients¹⁸.

Fish oil has mild antiplatelet effects at high doses, weaker than aspirin, and may raise INR when taken with warfarin¹⁹. In large trials, mostly in people not on anticoagulants, it didn't raise bleeding overall²⁰. A 2024 meta-analysis of 11 randomized trials in 120,643 people found a bleeding rate ratio of 1.09 (95% CI 0.91-1.31), which was not significant²⁰.

• High-dose purified EPA: bleeding rose by 50% in relative terms, but only by 0.6% in absolute terms²⁰.
• With warfarin: in a small randomized trial of 16 patients, 3 g or 6 g of fish oil daily for 4 weeks didn't change INR²¹. NIH notes a case report of a raised INR¹⁹.
• Monitoring: prescription omega-3 labels still advise periodic INR checks when they are taken with anticoagulants¹⁹.

So omega-3 has a mild effect on platelets, nothing like an anticoagulant. But the meta-analysis checked only background antiplatelet use, with no anticoagulant subgroup, so it can't show safety on apixaban, rivaroxaban or warfarin²⁰. Tell your prescriber before starting it, especially a high-dose EPA product, and expect an INR check on warfarin^{19, 20}.

Turmeric isn't a proven blood thinner, but there is a signal worth respecting. A 2025 review lists curcumin among herbs that may raise bleeding risk when combined with antithrombotic drugs¹⁶. A French pharmacovigilance team reported a probable case of a raised INR after turmeric was added to a warfarin-type drug¹⁵.

No controlled trial has tested curcumin with apixaban or rivaroxaban, so we can't put a number on the risk. Cooking amounts are different from capsules. NIH advises talking to your provider before using any herbal product with a medicine, and warns of liver injury with high-bioavailability curcumin products²².

If you want turmeric for joint pain, ask first and avoid stacking it with ginkgo, garlic or ginger capsules. Our guide to ginger and turmeric shots covers the amounts in those drinks.

Most of the herbs with a reputation for thinning blood haven't changed INR in controlled trials. The warnings come from case reports and lab mechanisms^{5, 10}.

• Ginkgo: in 24 stable warfarin patients, 100 mg daily for 4 weeks didn't change the weekly warfarin dose¹⁷. NIH still warns it may raise bleeding risk with warfarin²³.
• Ginger: it didn't change INR in 12 healthy men given one warfarin dose²⁴. A 2025 review still lists ginger, even in small amounts, as able to boost warfarin¹².
• Garlic: aged garlic extract, 5 mL twice daily for 12 weeks, didn't increase bleeding in 48 warfarin patients²⁵. The warfarin label says garlic may cause bleeding on its own¹¹.
• Vitamin E: in 21 warfarin patients, vitamin E didn't change INR²⁶. NIH says large doses can raise bleeding risk, probably above 400 IU a day, especially when vitamin K intake is low¹³.
• CoQ10: 100 mg daily didn't change warfarin needs in the same 24-patient trial¹⁷.
• Cranberry: 240 mL of juice daily for 2 weeks didn't change warfarin levels in 30 patients²⁷. But 2 weeks of a cranberry product raised the INR curve after one warfarin dose by 30% in 12 healthy men²⁸.
• Glucosamine: one man's INR rose from 2.3 to 3.9 after he raised his glucosamine dose¹⁴. The WHO database held 21 similar reports, and 17 resolved when glucosamine was stopped¹⁴.

A null result in 12 to 48 people doesn't rule out a rare bleed^{24, 25}. Treat these as "tell your prescriber and monitor", not as safe or banned.

Supplements in this guide

• Ginkgo Biloba
• Garlic Extract
• Vitamin E
• CoQ10
• Cranberry Extract
• Glucosamine

Yes, as far as the labels go: none of the warfarin, apixaban or rivaroxaban labels names magnesium, vitamin D or vitamin B12 as an interacting product^{11, 1, 2}. That covers magnesium with Eliquis, a common worry.

• Vitamin D3 with K2 on Eliquis or Xarelto: vitamin K is not expected to change these drugs' effect^{1, 2}.
• Vitamin D3 with K2 on warfarin: the K2 part counts as a vitamin K change, so check with your clinic first^{9, 4}.
• Multivitamins: many contain vitamin K. On warfarin, consistency from food and supplements is what matters, so pick one product and take it every day⁴.

Plain vitamin D and vitamin B12 don't appear on the labels' interaction lists^{11, 1, 2}. Still list them for your pharmacist.

No food works as a blood thinner, but a few can strengthen warfarin: ginger, even in small amounts, and eating more than one mango¹². Foods high in vitamin K do the opposite, lowering the INR if you suddenly eat more of them and raising it if you suddenly stop⁴. The warfarin label asks for a normal, balanced diet with a consistent amount of vitamin K, and no drastic changes such as eating large amounts of greens¹¹. For reference, adult women need 90 mcg a day and men 120 mcg⁴.

Vitamin K per serving, from NIH's food table⁴:

• Natto, 3 oz: 850 mcg (as MK-7)
• Collard greens, boiled, ½ cup: 530 mcg
• Turnip greens, boiled, ½ cup: 426 mcg
• Spinach, raw, 1 cup: 145 mcg
• Kale, raw, 1 cup: 113 mcg
• Broccoli, boiled, ½ cup: 110 mcg
• Blueberries, ½ cup: 14 mcg
• Olive oil, 1 tablespoon: 8 mcg
• Egg, 1 large: 4 mcg

So broccoli is fine on warfarin if you eat it regularly, and blueberries and olive oil carry little vitamin K. A 2016 systematic review found that restricting vitamin K doesn't improve control; an effect showed up mainly above about 150 mcg a day²⁹. A 2025 review advises caution with greens supplying more than 250 mcg a day¹².

On apixaban or rivaroxaban, greens don't matter. Apixaban can be taken with or without food, but rivaroxaban 15 mg and 20 mg tablets should be taken with food^{1, 2}.

The highest risk is in people who stack several things that affect bleeding. Both newer drugs' labels warn that aspirin, other antiplatelets, NSAIDs such as ibuprofen, SSRIs and SNRIs raise bleeding risk^{1, 2}. In a survey of 791 people on apixaban, 33% took at least one product with a potentially serious interaction daily or most days³⁰.

• People also on aspirin, NSAIDs or an SSRI: adding ginkgo, garlic, high-dose vitamin E or turmeric stacks more bleeding mechanisms on top^{1, 11, 13}. See our guide to SSRIs and supplements.
• People on warfarin who change routine: starting or stopping any botanical calls for more frequent INR checks¹¹.
• Pregnancy: turmeric supplements may be unsafe in pregnancy, and ginkgo might cause extra bleeding during delivery^{22, 23}.
• People treated for a clot or stroke: after a deep vein thrombosis or ischemic stroke, St. John's wort is the clearest danger, because it lowers drug levels^{1, 2}.

Report signs of bleeding straight away: unusual bruising, nosebleeds, bleeding gums, pink or brown urine, red or black stools, or vomiting blood¹¹.

About 66% of the apixaban patients were unsure or wrong about the bleeding risk of NSAIDs³⁰. If you're unsure about a product, ask your pharmacist before you buy it.

Change one thing at a time and tell the person who manages your anticoagulant. The warfarin label asks for more frequent INR monitoring when starting or stopping botanicals¹¹.

• On warfarin: start the supplement, then get an INR check within your clinic's usual window. Keep the same product and dose every day, because vitamin K swings are what move INR^{11, 4}.
• On apixaban or rivaroxaban: standard clotting tests such as INR aren't useful for monitoring apixaban, so an interaction won't show up on a routine blood test¹. Avoid anything with St. John's wort, and ask before adding anything that affects platelets^{1, 2}.
• Stopping a supplement: stopping matters as much as starting. Stopping St. John's wort or vitamin K changes warfarin's effect in the opposite direction^{11, 4}.
• Before surgery or dental work: list every supplement for the team, including fish oil, ginkgo and vitamin E^{19, 23, 13}.

A practical rule: if a product's label mentions blood flow, circulation or clot support, assume it may interact and ask first.

Supplements in this guide

• St. Johns Wort
• Vitamin K1
• Vitamin K2
• Omega-3 Fatty Acids
• Turmeric
• Nattokinase

We searched PubMed for systematic reviews, randomized trials and case reports on warfarin, apixaban and rivaroxaban with foods, herbs and supplements. We read 23 abstracts and cited 22, and read the NIH fact sheets on vitamin K, omega-3s and vitamin E, two NCCIH herb pages and the three drug labels on DailyMed. We gave the most weight to the labels, systematic reviews and controlled trials. Most herb trials enrolled 12-48 people, often healthy men given one warfarin dose, so they can miss rare bleeds. Evidence for apixaban and rivaroxaban is mostly label data. Researched on 15 October 2026.

1. Apixaban (Eliquis) tablets: prescribing information. DailyMed, U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/services/v2/spls/e9481622-7cc6-418a-acb6-c5450daae9b0.xml
2. Rivaroxaban (Xarelto) tablets: prescribing information. DailyMed, U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/services/v2/spls/10db92f9-2300-4a80-836b-673e1ae91610.xml
3. Jiang X, et al. Effect of St John's wort and ginseng on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects. Br J Clin Pharmacol. 2004;57(5):592-9. doi:10.1111/j.1365-2125.2003.02051.x
4. National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/
5. Holbrook AM, et al. Systematic overview of warfarin and its drug and food interactions. Arch Intern Med. 2005;165(10):1095-106. doi:10.1001/archinte.165.10.1095
6. Sconce E, et al. Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin. Blood. 2007;109(6):2419-23. doi:10.1182/blood-2006-09-049262
7. Boonyawat K, et al. The effect of low-dose oral vitamin K supplementation on INR stability in patients receiving warfarin. A randomised trial. Thromb Haemost. 2016;116(3):480-5. doi:10.1160/TH16-04-0320
8. Mahtani KR, et al. Vitamin K for improved anticoagulation control in patients receiving warfarin. Cochrane Database Syst Rev. 2014;2014(5):CD009917. doi:10.1002/14651858.CD009917.pub2
9. Theuwissen E, et al. Effect of low-dose supplements of menaquinone-7 (vitamin K2 ) on the stability of oral anticoagulant treatment: dose-response relationship in healthy volunteers. J Thromb Haemost. 2013;11(6):1085-92. doi:10.1111/jth.12203
10. Tan CSS, et al. Warfarin and food, herbal or dietary supplement interactions: A systematic review. Br J Clin Pharmacol. 2021;87(2):352-374. doi:10.1111/bcp.14404
11. Warfarin sodium tablets: prescribing information. DailyMed, U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/services/v2/spls/19a69a72-ac5d-45d5-a94d-a5aaecbe4730.xml
12. Talasaz AH, et al. Pharmacokinetic and Pharmacodynamic Interactions between Food or Herbal Products and Oral Anticoagulants: Evidence Review, Practical Recommendations, and Knowledge Gaps. Semin Thromb Hemost. 2025;51(5):560-571. doi:10.1055/s-0044-1790258
13. National Institutes of Health, Office of Dietary Supplements. Vitamin E: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminE-HealthProfessional/
14. Knudsen JF, et al. Potential glucosamine-warfarin interaction resulting in increased international normalized ratio: case report and review of the literature and MedWatch database. Pharmacotherapy. 2008;28(4):540-8. doi:10.1592/phco.28.4.540
15. Daveluy A, et al. Probable interaction between an oral vitamin K antagonist and turmeric (Curcuma longa). Therapie. 2014;69(6):519-20. doi:10.2515/therapie/2014062
16. Dobre MZ, et al. Navigating the Effects of Anti-Atherosclerotic Supplements and Acknowledging Associated Bleeding Risks. Int J Mol Sci. 2025;26(20). doi:10.3390/ijms262010183
17. Engelsen J, et al. [Effect of Coenzyme Q10 and Ginkgo biloba on warfarin dosage in patients on long-term warfarin treatment. A randomized, double-blind, placebo-controlled cross-over trial]. Ugeskr Laeger. 2003;165(18):1868-71. https://pubmed.ncbi.nlm.nih.gov/12772396/
18. Grześk G, et al. The Clinical Significance of Drug-Food Interactions of Direct Oral Anticoagulants. Int J Mol Sci. 2021;22(16). doi:10.3390/ijms22168531
19. National Institutes of Health, Office of Dietary Supplements. Omega-3 Fatty Acids: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/Omega3FattyAcids-HealthProfessional/
20. Javaid M, et al. Bleeding Risk in Patients Receiving Omega-3 Polyunsaturated Fatty Acids: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. J Am Heart Assoc. 2024;13(10):e032390. doi:10.1161/JAHA.123.032390
21. Bender NK, et al. Effects of Marine Fish Oils on the Anticoagulation Status of Patients Receiving Chronic Warfarin Therapy. J Thromb Thrombolysis. 1998;5(3):257-261. doi:10.1023/A:1008852127668
22. National Center for Complementary and Integrative Health. Turmeric: Usefulness and Safety. https://www.nccih.nih.gov/health/turmeric
23. National Center for Complementary and Integrative Health. Ginkgo: Usefulness and Safety. https://www.nccih.nih.gov/health/ginkgo
24. Jiang X, et al. Effect of ginkgo and ginger on the pharmacokinetics and pharmacodynamics of warfarin in healthy subjects. Br J Clin Pharmacol. 2005;59(4):425-32. doi:10.1111/j.1365-2125.2005.02322.x
25. Macan H, et al. Aged garlic extract may be safe for patients on warfarin therapy. J Nutr. 2006;136(3 Suppl):793S-795S. doi:10.1093/jn/136.3.793S
26. Kim JM, et al. Effect of vitamin E on the anticoagulant response to warfarin. Am J Cardiol. 1996;77(7):545-6. doi:10.1016/s0002-9149(97)89357-5
27. Ansell J, et al. The absence of an interaction between warfarin and cranberry juice: a randomized, double-blind trial. J Clin Pharmacol. 2009;49(7):824-30. doi:10.1177/0091270009337510
28. Mohammed Abdul MI, et al. Pharmacodynamic interaction of warfarin with cranberry but not with garlic in healthy subjects. Br J Pharmacol. 2008;154(8):1691-700. doi:10.1038/bjp.2008.210
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30. Tarn DM, et al. Prevalence and Knowledge of Potential Interactions Between Over-the-Counter Products and Apixaban. J Am Geriatr Soc. 2020;68(1):155-162. doi:10.1111/jgs.16193