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Anticoagulants (Warfarin)

Warfarin is a vitamin-K-antagonist anticoagulant with a narrow therapeutic window measured by INR.

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A medication reference built from the interaction graph. It is not prescribing information — the label and your prescriber are.

What is uncertain

Read off the same rows as above. Nothing here is added that the entry does not itself record.

  • Caution with Vitamin K2: Antagonizes vitamin-K-antagonist anticoagulants; keep intake constant and clear it medically.
  • Caution with Vitamin C: Gram-plus doses can swing INR; keep intake consistent.
  • Caution with Vitamin E: High-dose E adds bleeding risk on anticoagulants.
  • Caution with Panax Ginseng: May reduce warfarin effect — monitor INR.
  • Caution with Curcumin (Turmeric): Mild antiplatelet action — additive bleeding risk.
  • Caution with St. John's Wort: Induces metabolism — reduces anticoagulant effect.
  • Caution with Ginkgo Biloba: Antiplatelet action — additive bleeding risk.
  • Caution with Garlic: Antiplatelet action — additive bleeding risk.
  • Caution with Algae Omega-3: High-dose omega-3 adds bleeding risk on anticoagulants.
  • Caution with Coenzyme Q10: May slightly reduce anticoagulant effect — monitor INR.
  • Caution with Resveratrol: Mild antiplatelet effect — additive bleeding risk.
  • Caution with Ginger: Mild antiplatelet — additive bleeding risk at high doses.
  • Caution with Reishi: Mild antiplatelet action — additive bleeding risk.
  • Caution with American Ginseng: May reduce warfarin effect — monitor INR.
  • Caution with Grape Seed Extract: Mild antiplatelet — additive bleeding risk.
  • Caution with Chlorella: Vitamin-K content can antagonize warfarin — keep intake consistent.
  • Caution with Vitamin K1: Directly antagonizes warfarin — keep intake consistent, never swing it.
  • Caution with Nattokinase: Fibrinolytic — additive bleeding risk with anticoagulants.
  • Caution with Bromelain: Mild antiplatelet — additive bleeding risk.
  • Caution with Horse Chestnut: Mild antiplatelet — additive bleeding risk.
  • Caution with Dong Quai: Coumarins add bleeding risk.
  • Caution with Omega-3: High-dose EPA/DHA adds bleeding risk on anticoagulants; keep under 1g without sign-off.
  • Caution with NSAIDs: Additive bleeding risk plus displacement — a dangerous, common combination.
  • Caution with Cinnamon: Cassia cinnamon's coumarin adds to anticoagulant effect at high intake.
  • Caution with Green Tea Extract (EGCG): Large amounts of green tea carry vitamin K and can affect anticoagulation — keep intake consistent.

Interactions

Documented pairings with supplements and medicines. A medicine on this list is a conversation for whoever prescribes it.

  • Vitamin K2Caution

    Antagonizes vitamin-K-antagonist anticoagulants; keep intake constant and clear it medically.

  • Vitamin CCaution

    Gram-plus doses can swing INR; keep intake consistent.

  • Vitamin ECaution

    High-dose E adds bleeding risk on anticoagulants.

  • Panax GinsengCaution

    May reduce warfarin effect — monitor INR.

  • Curcumin (Turmeric)Caution

    Mild antiplatelet action — additive bleeding risk.

  • St. John's WortCaution

    Induces metabolism — reduces anticoagulant effect.

  • Ginkgo BilobaCaution

    Antiplatelet action — additive bleeding risk.

  • GarlicCaution

    Antiplatelet action — additive bleeding risk.

  • Algae Omega-3Caution

    High-dose omega-3 adds bleeding risk on anticoagulants.

  • Coenzyme Q10Caution

    May slightly reduce anticoagulant effect — monitor INR.

  • ResveratrolCaution

    Mild antiplatelet effect — additive bleeding risk.

  • GingerCaution

    Mild antiplatelet — additive bleeding risk at high doses.

  • ReishiCaution

    Mild antiplatelet action — additive bleeding risk.

  • American GinsengCaution

    May reduce warfarin effect — monitor INR.

  • Grape Seed ExtractCaution

    Mild antiplatelet — additive bleeding risk.

  • ChlorellaCaution

    Vitamin-K content can antagonize warfarin — keep intake consistent.

  • Vitamin K1Caution

    Directly antagonizes warfarin — keep intake consistent, never swing it.

  • NattokinaseCaution

    Fibrinolytic — additive bleeding risk with anticoagulants.

  • BromelainCaution

    Mild antiplatelet — additive bleeding risk.

  • Horse ChestnutCaution

    Mild antiplatelet — additive bleeding risk.

  • Dong QuaiCaution

    Coumarins add bleeding risk.

  • Omega-3Caution

    High-dose EPA/DHA adds bleeding risk on anticoagulants; keep under 1g without sign-off.

  • NSAIDsCaution

    Additive bleeding risk plus displacement — a dangerous, common combination.

  • CinnamonCaution

    Cassia cinnamon's coumarin adds to anticoagulant effect at high intake.

  • Green Tea Extract (EGCG)Caution

    Large amounts of green tea carry vitamin K and can affect anticoagulation — keep intake consistent.

The evidence in words

What it is

Warfarin is a vitamin-K-antagonist anticoagulant with a narrow therapeutic window measured by INR.

How it works

It blocks the recycling of vitamin K needed to make clotting factors. Anything that changes vitamin K intake, platelet function, or its metabolism swings the INR.

What it's used for

Atrial fibrillation, mechanical heart valves, and venous thromboembolism.

Supplement & drug interactions

Anticoagulants (Warfarin) has 25 documented interactions mapped below and in the interactions graph. Two interaction themes: keep vitamin K (greens, K1/K2 supplements) steady — never swing it — and avoid stacking antiplatelet supplements (high-dose fish oil, garlic, ginkgo, vitamin E, ginger, nattokinase) that add bleeding risk. Everything here goes through the anticoagulation clinic.

The rule

This is a medication reference for spotting interactions, not dosing advice. Every change to a supplement stack around a prescription belongs with the person who prescribes it.

Related reading

Entries that share this one's tags or conditions.

  • DOACsDirect oral anticoagulants — newer blood thinners that, unlike warfarin, need no routine INR monitoring.Evidence grade A
  • AntiplateletsDrugs that reduce platelet clumping to prevent arterial clots.Evidence grade A
  • ADHD StimulantsPrescription stimulants for attention-deficit/hyperactivity disorder.Evidence grade A
  • Blood-Pressure MedicationsThe families of drugs that lower blood pressure — ACE inhibitors, ARBs, calcium-channel blockers, beta-blockers.Evidence grade A

Sources

This entry lists no references of its own.

Last revised . A grade is this entry's reading of the evidence, not medical advice.