Our Members Asked:
I take warfarin (Coumadin), an anticoagulant drug. Are there supplements I should avoid, or be taking, due to this drug?

Answer:
Yes, the effectiveness of warfarin (Coumadin), anisindione (Miradon) and other anticoagulant drugs prescribed to prevent blood clots can be impacted by taking supplements. Because it can be affected by a large number of herbs, supplements and foods, it's important to consult your physician before taking any supplement with warfarin.
Below are some examples of supplements that may potentially interact with warfarin. Some increase or decrease the breakdown warfarin in the body, which, correspondingly, may reduce or increase the effects of warfarin. Others have their own blood-thinning or clot-promoting effects, which, correspondingly, may increase or reduce the effectiveness of warfarin. More details can be found by clicking on the links below. Also, discussed below are supplements that can interact with, or be affected by, the non-steroidal anti-inflammatory drug (NSAID) aspirin.
Supplements that may increase warfarin's blood-thinning effect by inhibiting its breakdown include:
- Bee pollen
- Berberine/goldenseal
- Black pepper extract (piperine or Bioperine) — a bioavailability enhancer in some curcumin and CoQ10 formulas
- CBD (cannabidiol)
- Grapefruit juice
- Kava
- Kratom
- Milk thistle
- Quercetin
Supplements that may increase warfarin's blood-thinning effect due to their own blood-thinning effect include:
- Ashwagandha
- Chamomile
- Chondroitin
- Cinnamon (high-dose)
- Cranberry
- Curcumin
- Digestive enzymes (i.e. papain and bromelain)
- Flaxseeds and flaxseed oil
- Fish oil
- Garlic
- Ginger
- Gingko
- Lumbrokinase
- Melatonin
- Nattokinase
- Niacin
- Resveratrol
- Saffron (including extracts such as Krocina)
Supplements that may reduce warfarin's blood-thinning effect by increasing its breakdown include:
Supplements that may promote clot formation, reducing the blood-thinning effects of warfarin, include the following:
Supplements that may affect, or be affected by, aspirin (another common blood thinner):
Vitamins that may affect aspirin:
- Vitamin E: High-dose vitamin E (~800 mg daily) may increase the blood thinning effects of aspirin and increase the risk of bleeding.
Vitamins and minerals that may be affected by aspirin:
- Iron: Long-term use of aspirin, even in low doses (100 mg daily), has been linked with lower body iron stores and 20% increased risk of anemia (McQuilten, Ann Intern Med 2023).
- Vitamin B-1 (thiamin): Aspirin may increase the urinary excretion of thiamin and decrease thiamin levels (Renaud, Nutrients 2024; Marrs, Cells 2021).
- Vitamin B-9 (folate): High doses (e.g., 3,900 mg daily) of aspirin may increase the urinary excretion of folate and decrease folate levels. Low-dose aspirin does not appear to have this effect (Renaud, Nutrients 2024).
- Vitamin C (ascorbic acid): People who take high doses (reported at 12 or more tablets daily), tend to have lower levels of vitamin C, but not if also taking a vitamin C supplement (Sahud, Lancet 1971).
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Stan19938
July 07, 2024It seems that even if one is not taking presciptiom medicines there is an issue with the COMBINED effects of many of the herbs & supplements listed with regard to possible excessive effects on either blood thinning or cloting ---as well as any interactions BETWEEN these herbs and supplements in that regard. That issue would seem difficult to assess and quantify as opposed to more straightforward / interactions with certain medications. And since your readers often DO take multiple herbs and supplements it can’t be ignored.
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raymond1596
April 27, 2023I’ve been on Xarelto for about 8 months and was also taking Nattokinase, Bromelain, and Resveratrol with Quercetin. My Dr had asked about supplements and I didn’t mention them because I assumed they didn’t matter. Thankfully, I haven’t had any problems outside of maybe some looser stool, but I’m stopping them now. No bruising or clotting problems. Better safe than sorry, though. Should I look for any bloodwork to search for kidney or liver damage?
There does not appear to be any strong evidence that nattokinase, bromelain, resveratrol or quercetin cause kidney or liver damage in most adults, but, as we note in our article about Xarelto, some of these supplements may increase the blood-thinning effects of Xarelto and similar medications: https://www.consumerlab.com/answers/supplement-interactions-with-apixaban-eliquis/eliquis-supplement-interactions/
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Margo1595
October 27, 2019Hi - I saw a board certified hematologist for some in-depth management of certain blood levels. I asked him point blank:
Should I manage my dosage of Warfarin to my diet, or should I manage my diet to the recommended dosage.
His response was unequivocal: Manage the dosage to your diet, testing as often as needed if your diet varies.
I have a congenital blood defect and clot easily. I have taken warfarin non-stop since 1992.
No additional incidents of DVT or pulmonary embolism. Must be doing something right!
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Michael W1592
November 07, 2016I take coumadin, and vitimain K and eat spinich/green salad almost every day. . The coumadin is adusted to my diet and the way to accomplish this is to be consistant with what I eat. I have to take a larger does of counadin to offset my green leaf salads and vitimin K intake then someone else who dies not take vit K and eat greens. , but I as long as I am reasonably consistant with my diest my numbers are good.
Carol1594
September 25, 2019How very excellent that your physician adjusted the drug to your diet! I wish this was standard practice. Every time I hear warnings about healthy food & drink "thinning the blood too much if you're on a blood thinner", my first thought is, instead of avoiding obviously healthy food & drink, why not decrease or eliminate the medication! (Of course no medication should be stopped cold turkey due to possible 'rebound' effects, and for this reason should only be done gradually, under a physician's supervision.)
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Donald1590
March 24, 2016I take warfarin because of A-Fib. I also take Co-Q10, Fish Oil, turmeric and use garlic and my last 6 INR's have been 2.3, 2.4, 2.4, 2.4, 2.2, 2.3. No problem, also eat broccoli, kale, and spinach.
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