Nattokinase as a Natural Blood Thinner

Every year, over 900,000 Americans develop a dangerous blood clot — and many of them are quietly looking for a safer long-term strategy than daily prescription anticoagulants.

Nattokinase, a fibrinolytic enzyme derived from the Japanese fermented food natto, has earned serious scientific attention as a natural blood thinner. It works differently from drugs like warfarin or aspirin — dissolving fibrin directly and amplifying the body's own clot-clearing system rather than blocking a single pathway. Clinical trials have measured real reductions in key clotting factors. But "natural" does not mean "risk-free," and the drug interaction picture is not simple.

This article covers what the evidence actually shows, where nattokinase falls short, and the critical safety conversations anyone on anticoagulant therapy must have with their doctor before adding it to their regimen.

Table of Contents

• 1. What Makes Nattokinase a Natural Blood Thinner?
• 2. How It Differs From Warfarin and Aspirin
• 3. The Clinical Evidence: Clotting Factor Reductions
• 4. Drug Interactions: The Most Important Section to Read
• 5. Who Should Not Take Nattokinase
• 6. BioAbsorb Nattokinase Enzyme — What to Look For in a Supplement
• Frequently Asked Questions
• Conclusion
• Research References

1. What Makes Nattokinase a Natural Blood Thinner?

The term "blood thinner" is slightly misleading — no substance literally thins your blood. What anticoagulants and fibrinolytic agents do is reduce the tendency of blood to form clots, or break down clots that have already formed. Nattokinase works on both fronts, which is what distinguishes it from most natural compounds in this space.

Nattokinase is a serine protease enzyme isolated from natto, a traditional Japanese food made from soybeans fermented with Bacillus subtilis natto. Its primary action is fibrinolysis — the enzymatic breakdown of fibrin, the protein scaffold that gives blood clots their structure. In vitro studies confirm that nattokinase directly cleaves cross-linked fibrin, breaking apart established clots at a molecular level. At an equivalent molar dose, research suggests nattokinase is approximately four times more effective than plasmin [2] at dissolving thrombus in rat models — a striking comparison given that plasmin is the body's primary clot-dissolving enzyme.

But nattokinase doesn't stop at direct fibrin dissolution. It also inhibits PAI-1 (plasminogen activator inhibitor-1), which is the body's primary brake on its own fibrinolytic system. PAI-1 blocks tissue plasminogen activator (tPA), the enzyme that would otherwise convert inactive plasminogen into plasmin. When nattokinase inactivates PAI-1, it effectively lifts that brake — allowing tPA to work more freely and accelerating the body's natural clot-clearing activity. Elevated PAI-1 is a recognized cardiovascular risk factor associated with thrombosis, atherosclerosis, and metabolic syndrome, making its inhibition clinically meaningful beyond simple clot dissolution.

A third mechanism adds to nattokinase's anticoagulant-like profile: it reduces the plasma levels of several key coagulation factors — fibrinogen, factor VII, and factor VIII — each of which plays a role in the clotting cascade that initiates thrombus formation. This multi-pathway action is why researchers have described nattokinase as a potent antithrombotic agent [3] rather than simply a fibrinolytic enzyme.

2. How It Differs From Warfarin and Aspirin

Understanding how nattokinase differs from prescription blood thinners matters — both for appreciating its potential and for understanding why it cannot simply substitute for medications your doctor has prescribed.

Warfarin (Coumadin) is a vitamin K antagonist. It works by blocking the production of clotting factors that depend on vitamin K, reducing the blood's overall capacity to form clots. It requires regular INR monitoring because the therapeutic window is narrow — too little and clots form; too much and serious bleeding occurs. Diet, other medications, and genetics all affect how warfarin behaves in any individual.

Aspirin and antiplatelet drugs work at the platelet level, preventing platelets from aggregating and forming the initial plug that starts a clot. Aspirin's blood-thinning effect is well-studied but comes with a meaningful tradeoff: it is associated with a 40% increased risk of major bleeding [8] events in primary prevention settings, with gastrointestinal bleeding being the most common concern.

Nattokinase takes a different approach. Rather than blocking clotting factor synthesis (warfarin's method) or preventing platelet aggregation (aspirin's method), it acts on clots that are already forming or present — dissolving fibrin directly and supporting the body's own fibrinolytic system. Research suggests nattokinase also has some antiplatelet effect, but this is a secondary mechanism rather than its primary action. This upstream, multi-pathway approach is pharmacologically distinct from both warfarin and aspirin.

The practical implication: nattokinase may be a reasonable proactive option for cardiovascular-conscious adults who are not on prescription anticoagulants. For anyone who is already on warfarin, DOACs (like apixaban or rivaroxaban), aspirin, or clopidogrel, the interaction picture changes significantly — which is covered in full in Section 4.

3. The Clinical Evidence: Clotting Factor Reductions

The strongest human evidence for nattokinase as a natural blood thinner comes from a 2009 study published in Nutrition Research by Hsia and colleagues. The trial enrolled 45 participants across three groups — healthy volunteers, patients with cardiovascular risk factors, and dialysis patients — all of whom took two nattokinase capsules daily (2000 FU per capsule) for two months. The results were consistent across all groups: fibrinogen fell by 7–10%, factor VII by 7–14%, and factor VIII by 17–19% [1]. No significant adverse events were observed.

These are not trivial reductions. Fibrinogen is a direct precursor to fibrin — the scaffolding of blood clots. Elevated fibrinogen is an independent cardiovascular risk marker. Factor VIII is critical to the intrinsic coagulation cascade; elevated factor VIII is associated with increased risk of venous thromboembolism. Meaningful reductions in all three, achieved through oral supplementation with no observed side effects, is a clinically interesting finding.

A 2015 study published in Scientific Reports (Nature) took a more granular look, tracking coagulation and fibrinolysis parameters at 2, 4, 6, and 8 hours after a single 2000 FU dose in 12 healthy young males. The study confirmed that a single dose measurably shifted both thrombolysis and anticoagulation profiles [2] within hours — factor VIII activity declined significantly at 4 and 6 hours, and antithrombin concentration rose at 2 and 4 hours.

A 2016 study by Jensen and colleagues, published in Integrated Blood Pressure Control, reported an additional relevant finding: nattokinase reduced von Willebrand factor — a clotting protein that rises in hypertensive patients — by roughly 15% over eight weeks in 79 participants. Von Willebrand factor is a recognized cardiovascular risk marker, and its reduction alongside blood pressure improvements adds another layer to nattokinase's cardiovascular profile.

Where the evidence is less complete: most trials are small, short-duration, and lack active comparators. There are no head-to-head trials comparing nattokinase to warfarin or DOACs in clinical populations. The evidence supports nattokinase as a meaningful fibrinolytic supplement — but it does not yet support positioning it as equivalent to pharmaceutical anticoagulation in high-risk patients. That distinction matters for anyone trying to make an evidence-informed decision.

4. Drug Interactions: The Most Important Section to Read

This is where nattokinase conversations need to be most careful — and where "natural" can become genuinely dangerous if the interaction picture is ignored.

Warfarin: This is the interaction that carries the highest documented concern. Nattokinase and warfarin both work in directions that reduce blood's clotting capacity, but through different mechanisms. Combined use may compound anticoagulant effects, potentially pushing INR above the therapeutic window and increasing the risk of serious bleeding. Memorial Sloan Kettering Cancer Center explicitly flags [6] that nattokinase may theoretically increase bleeding risk when combined with anticoagulant, antiplatelet, and fibrinolytic drugs. An unpublished study cited by clinical pharmacology databases also reported that co-administration of nattokinase with heparin, aspirin, or clopidogrel in stroke patients increased bleeding time and clotting time. If you take warfarin, do not add nattokinase without first consulting your prescribing physician and arranging closer INR monitoring.

DOACs (Direct Oral Anticoagulants): Drugs like apixaban (Eliquis), rivaroxaban (Xarelto), and dabigatran (Pradaxa) are increasingly common, particularly for atrial fibrillation and DVT prevention. The interaction data between nattokinase and DOACs is less studied than the warfarin literature, but the theoretical concern is the same: combining two agents that suppress coagulation activity increases bleeding risk. Anyone on a DOAC should treat nattokinase with the same caution as warfarin and discuss it with their cardiologist or hematologist before use.

Aspirin and antiplatelet drugs: Aspirin, clopidogrel (Plavix), and ticagrelor reduce platelet aggregation. Nattokinase has its own antiplatelet-like effects. Combining the two may amplify bleeding risk, particularly gastrointestinal bleeding. This includes low-dose aspirin taken for cardiovascular prevention — even at 81 mg daily, the interaction warrants disclosure to your doctor.

Pre-surgery discontinuation: Nattokinase's effects on coagulation and fibrinolysis persist for a measurable window after a dose. Pharmacokinetic data suggests enzyme activity is detectable for up to 48 hours after a single dose. For elective surgery, stopping nattokinase at least one week in advance is a reasonable conservative approach — similar to guidance for fish oil and other supplements that affect hemostasis. Inform your surgeon and anesthesiologist about nattokinase use during pre-operative evaluation.

The core principle: nattokinase's antithrombotic, fibrinolytic, and antiplatelet activities [7] are precisely what make it interesting as a cardiovascular supplement — and precisely what make it potentially dangerous in combination with drugs that work through overlapping mechanisms. Transparency with your healthcare provider is not optional here.

5. Who Should Not Take Nattokinase

The cardiovascular research on nattokinase is promising, but that promise comes with a clear set of contraindications. This section is about being honest regarding who should not take this supplement without direct physician involvement — or at all.

People currently taking prescription blood thinners. As detailed in Section 4, combining nattokinase with warfarin, DOACs, aspirin, or antiplatelet drugs carries a meaningful and not fully characterized bleeding risk. This does not mean the combination is always dangerous — but it does mean it requires medical supervision and should not be self-initiated.

People with a history of bleeding disorders. Hemophilia, von Willebrand disease, and other conditions that already impair normal clotting make nattokinase's fibrinolytic activity a significant risk factor. Nattokinase further reduces the capacity to form clots — a potentially dangerous compounding effect.

People scheduled for surgery or invasive procedures. The pre-surgical discontinuation window discussed in Section 4 applies here. Even minor procedures that carry bleeding risk — dental extractions, colonoscopies, biopsies — warrant a conversation with your provider and likely a stoppage of nattokinase in advance.

People who have had a hemorrhagic stroke. Hemorrhagic stroke involves bleeding in the brain, not a clot. Nattokinase's fibrinolytic activity is entirely contraindicated in this context. For ischemic stroke (caused by a clot), nattokinase has been studied, but this remains an area requiring physician guidance rather than self-supplementation.

Pregnant and breastfeeding individuals. There is no meaningful safety data on nattokinase use during pregnancy or lactation. The default position, consistent with general supplement guidance, is to avoid it until evidence exists.

For adults without these contraindications — those proactively managing cardiovascular health, with no prescription anticoagulants and no bleeding history — nattokinase's clinical trial safety record is reassuring. The 2009 Hsia trial found no significant adverse events across 45 participants over two months, and multiple other trials have reported similar tolerability. But the absence of serious adverse events in small, short trials is not the same as a comprehensive long-term safety profile.

6. BioAbsorb Nattokinase Enzyme — What to Look For in a Supplement

If you and your healthcare provider have determined that nattokinase is appropriate for your situation, the quality of the supplement you choose has a direct bearing on whether you're getting the dose the research actually used.

The standard in clinical trials is 2000 FU (fibrinolytic units) per capsule — this is the dose studied in the Hsia 2009 trial, the Scientific Reports 2015 single-dose study, and the Jensen 2016 blood pressure trial. Fibrinolytic units measure enzymatic activity, not simply milligram weight. Two products could both list "100 mg" on the label but contain very different amounts of active enzyme if manufacturing quality varies. FU standardization is what makes a dose meaningful.

Delivery technology also matters. Nattokinase is a protein enzyme. Without protection from stomach acid, a significant portion degrades before reaching the small intestine, where absorption occurs. Standard capsules offer no protection. Enteric-coated capsules address this but often use phthalate-based coatings that carry their own concerns.

BioAbsorb Nattokinase Enzyme delivers 100 mg standardized to 2000 FU per capsule, using DRcaps — a delayed-release veggie capsule technology that protects the enzyme through the acidic stomach environment and releases it intact in the small intestine. DRcaps are free of the phthalates and plasticizers found in many standard enteric-coated capsules, which matters for health-conscious consumers who read ingredient labels carefully.

The formulation is non-GMO, free of gluten, nuts, eggs, dairy, fish, shellfish, and all animal products, and 100% vegetarian. Each batch is third-party tested for nattokinase activity (≥2000 FU confirmed), heavy metals, gluten, and microbial contaminants. Manufacturing takes place in a GMP-certified facility in Canada. The product is also free of vitamin K2 — an important distinction, since raw natto contains high levels of K2 that can interfere with warfarin. Removing K2 from the extract eliminates that specific warfarin interaction variable, though nattokinase's direct fibrinolytic activity still requires physician disclosure if you are on anticoagulant therapy.

At $49.87 for 180 capsules, BioAbsorb Nattokinase works out to approximately $0.28 per day — a 180-day supply at one capsule daily, taken on an empty stomach for optimal delivery. Visit BioAbsorb Nutraceuticals for full product details and current availability.

Frequently Asked Questions

Is nattokinase as strong as warfarin for thinning the blood?

No — and this comparison is worth being direct about. Warfarin is a pharmaceutical anticoagulant with a precisely titratable effect, monitored through regular INR testing. Nattokinase is a nutraceutical with measurable fibrinolytic and anticoagulant-like effects, but its potency is significantly lower and less predictable than therapeutic warfarin dosing. For high-risk indications like atrial fibrillation or mechanical heart valves, nattokinase is not an appropriate substitute for prescribed anticoagulation. For proactive cardiovascular support in lower-risk individuals, it may offer meaningful benefit. These are genuinely different use cases.

Can I take nattokinase if I already take a daily baby aspirin?

This is one of the most common questions, and the honest answer is: discuss it with your doctor before combining them. Both aspirin (at any dose) and nattokinase have antiplatelet-like effects. Combined use may increase bleeding risk, particularly GI bleeding, which is already a concern with regular aspirin use. This doesn't mean the combination is definitely dangerous for everyone — but it's not a self-managed decision. Your prescribing physician can evaluate your specific cardiovascular risk profile and advise accordingly.

How long does it take for nattokinase to work as a natural blood thinner?

The 2015 Scientific Reports study showed measurable changes in coagulation parameters within 2–4 hours of a single 2000 FU dose, suggesting relatively rapid enzyme activity. For sustained reductions in fibrinogen and clotting factors, the Hsia 2009 trial ran for two months before measuring significant changes — suggesting that meaningful cardiovascular benefit from repeated supplementation accumulates over weeks rather than days. Onset of fibrinolytic activity is relatively fast; meaningful changes in cardiovascular risk markers take longer.

Does nattokinase contain vitamin K2? Does that affect warfarin?

Raw natto — the fermented food — is very high in vitamin K2, which does interfere with warfarin's mechanism (since warfarin works by blocking vitamin K-dependent clotting factors). However, most commercially produced nattokinase supplements are extracted from natto in a process that removes vitamin K2. The BioAbsorb Nattokinase Enzyme formulation is explicitly free of vitamin K2, which eliminates this specific interaction variable. That said, nattokinase's direct fibrinolytic activity still poses a theoretical compounding risk with warfarin through a separate mechanism — so physician disclosure remains essential regardless of K2 content.

Should I stop taking nattokinase before surgery?

Yes, and it's worth stopping earlier than you might assume. Nattokinase's enzyme activity persists for at least 48 hours after a single dose based on pharmacokinetic data. A conservative approach — consistent with guidance for fish oil and other hemostasis-affecting supplements — is to discontinue nattokinase at least one week before any elective surgery or invasive procedure. For minor procedures, shorter discontinuation periods may be sufficient, but the decision should be made in consultation with your surgeon. Always disclose nattokinase use during pre-operative evaluation.

What is the recommended dose of nattokinase for blood-thinning effects?

The most consistently used dose in clinical research is 2000 FU per day — one capsule standardized to 2000 fibrinolytic units, taken on an empty stomach. This is the dose used in the Hsia 2009 fibrinogen reduction trial, the Jensen 2016 von Willebrand factor study, and the Scientific Reports 2015 single-dose coagulation study. Taking nattokinase on an empty stomach is important because food in the stomach can reduce enzymatic activity before absorption. For further guidance on dosing and timing, see the Nattokinase Dosage Guide.

Conclusion

Nattokinase earns its description as a natural blood thinner — the clinical evidence for its fibrinolytic action, PAI-1 inhibition, and reductions in fibrinogen and clotting factors is real and meaningful. For cardiovascular-conscious adults who are not on prescription anticoagulants and have no bleeding history, it represents one of the more evidence-supported natural options for proactive clot prevention. The drug interaction picture — particularly with warfarin, DOACs, and aspirin — requires honest conversation with a physician before use, not as a formality, but because the consequences of getting this wrong are serious. If you're ready to explore nattokinase with appropriate medical context, BioAbsorb Nattokinase Enzyme delivers the clinically studied 2000 FU dose with DRcaps delayed-release technology and full third-party testing transparency.

Research References

1. Nattokinase decreases plasma levels of fibrinogen, factor VII, and factor VIII in human subjects. Nutrition Research, Vol. 29, No. 3 (2009). Open-label self-controlled trial in 45 participants across healthy, cardiovascular, and dialysis groups; two months of 2000 FU twice daily produced significant reductions in fibrinogen (7–10%), factor VII (7–14%), and factor VIII (17–19%) with no adverse events observed.
2. A single-dose of oral nattokinase potentiates thrombolysis and anti-coagulation profiles. Scientific Reports (Nature Publishing Group), Vol. 5 (2015). Double-blind placebo-controlled crossover study in 12 healthy males; a single 2000 FU dose measurably elevated antithrombin concentrations and reduced factor VIII activity within 2–6 hours of administration.
3. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Integrative Blood Pressure Control, Vol. 11 (2018). Comprehensive peer-reviewed review of nattokinase's fibrinolytic mechanisms, PAI-1 inhibition, tPA enhancement, and antiplatelet activity across human and animal studies.
4. Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor. Integrated Blood Pressure Control, Vol. 9 (2016). Randomized, double-blind, placebo-controlled multicenter North American trial in 79 hypertensive participants; 8 weeks of nattokinase reduced von Willebrand factor by approximately 15% alongside blood pressure reductions.
5. Nattokinase: An Oral Antithrombotic Agent for the Prevention of Cardiovascular Disease. International Journal of Molecular Sciences, Vol. 18 (2017). Peer-reviewed review covering nattokinase history, mechanism of action, safety data, and current clinical trial status including the NAPS Phase II US trial.
6. Nattokinase — Drug Interactions and Safety Profile. Memorial Sloan Kettering Cancer Center, Integrative Medicine (2024). Authoritative clinical resource noting theoretical increased bleeding risk when nattokinase is combined with anticoagulant, antiplatelet, and fibrinolytic drugs; covers PAI-1 inactivation mechanism and warfarin interaction considerations.
7. Nattokinase — Clinical Pharmacology and Drug Interactions. Drugs.com Natural Products database (2024). Comprehensive drug interaction database entry covering warfarin, heparin, aspirin, and clopidogrel co-administration findings, including unpublished study data from ischemic stroke patients co-administered nattokinase at 6000 FU/day.
8. Pros and Cons of Aspirin for Primary Prevention of Cardiovascular Events. Frontiers in Medicine, Vol. 8 (2021). Meta-analysis finding aspirin associated with 40% increased risk of major bleeding events in primary prevention settings, contextualizing the relative risk profile of antiplatelet therapy.
9. Nattokinase as a functional food ingredient: therapeutic applications and mechanisms in age-related diseases. Functional Food Science, ScienceDirect (2024). Reviews pharmacokinetic evidence that 2000 FU NK produces peak serum levels at approximately 13 hours post-dose and confirms fibrinolytic activity between 2–8 hours after intake.
10. Forecasting the Burden of Cardiovascular Disease and Stroke in the United States Through 2050. Circulation — American Heart Association Presidential Advisory (2024). Projects hypertension prevalence rising from 51.2% to 61.0% by 2050, with CVD affecting approximately 28.6 million adults as of 2020, providing context for the scale of cardiovascular risk in the target population.

About the Author

David Kimbell is a health writer, digital entrepreneur and former aerospace engineer, based in Ottawa, Canada. He loves translating complex science into clear, actionable guidance for consumers seeking evidence-based solutions.

---

Important Disclaimers

Medical Disclaimer: This article provides educational information only and is not intended as medical advice. Always consult with a qualified healthcare provider before starting any new supplement, especially if you have existing health conditions, take medications, or are pregnant or nursing.

FDA/Health Canada Statement: These statements have not been evaluated by the Food and Drug Administration or Health Canada. This product is not intended to diagnose, treat, cure, or prevent any disease.