NutriStack
Nattokinase and Warfarin, a caution.
Nattokinase is a fibrinolytic enzyme that degrades fibrin directly and reduces clotting factors. Combined with warfarin, the additive effects substantially increase bleeding risk. Case reports describe hemoperitoneum and intracerebral hemorrhage with nattokinase in patients on other antithrombotics, and substituting nattokinase for warfarin has caused mechanical valve thrombosis.
One pair, every claim cited. The two substances, the type, the mechanism, the recommendation, and the primary literature.
Same shape as the other 1,729 pairs in the public database.
From the interaction database
What the row says.
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At a glance
- Substances
- Nattokinase and Warfarin
- Pair type
- Caution
- Evidence (highest tier)
- Moderate
- Source citations
- 2 sources
- Stack Score effect
- −5 to your Stack Score (per scored caution row).
- Scope
- Supplement × Prescription
- Last verified
- May 30, 2026
Caution · Moderate evidence
Caution
What is happening. Nattokinase is a fibrinolytic enzyme that degrades fibrin directly and reduces clotting factors. Combined with warfarin, the additive effects substantially increase bleeding risk. Case reports describe hemoperitoneum and intracerebral hemorrhage with nattokinase in patients on other antithrombotics, and substituting nattokinase for warfarin has caused mechanical valve thrombosis.
Mechanism. Nattokinase is a serine protease from fermented soybeans that cleaves fibrin directly and indirectly activates the fibrinolytic system by converting plasminogen to plasmin. It also reduces fibrinogen, factor VII, and factor VIII levels. These effects add to warfarin's reduction of clotting factor synthesis.
Recommendation. Do not combine nattokinase with warfarin. Never substitute nattokinase for prescribed warfarin, especially after mechanical valve replacement or for atrial fibrillation. If you have started nattokinase, stop it and contact your anticoagulation clinic.
Sources (2)
- Chang YY, Liu JS, Lai SL, Wu HS, Lan MY. Cerebellar hemorrhage provoked by combined use of nattokinase and aspirin in a patient with cerebral microbleeds. Intern Med. 2008;47(5):467-9. PMID 18310985
- Elahi MM, Choi CH, Konda S, Shake JG. Consequence of patient substitution of nattokinase for warfarin after aortic valve replacement with a mechanical prosthesis. Proc (Bayl Univ Med Cent). 2015;28(1):81-2. PMID 25552810
Stack Score
How this pair moves the number.
Effect on the composite score
If both Nattokinase and Warfarin are in the same stack, this pair applies −5 to your Stack Score (per scored caution row).
The full algorithm, the clamping rules, and four worked stacks are documented at /methodology/stack-score.
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