Nattokinase and Blood Thinners: What You Need to Know

Key Takeaways:

• Nattokinase and blood thinners should not be combined without medical supervision. Both act on the body's clotting system, and the combined effect may be stronger than either one alone.
• Nattokinase taken alone has a strong safety record: 1,062 participants took 10,800 FU of nattokinase daily for 12 months with no serious adverse events (Chen et al., 2022).
• That safety evidence does not cover combinations. Major nattokinase trials excluded participants on anticoagulant therapy, so combination safety has not been established.
• Never stop a prescribed blood thinner on your own. If you are interested in nattokinase, bring it up with the physician who manages your medication.

Whether nattokinase is safe to take alongside blood thinners is one of the most common questions about this enzyme, and it deserves a careful answer. Nattokinase and blood thinners both affect the clotting system, so combining them without medical supervision can raise bleeding risk in ways neither your doctor nor your supplement label accounted for.

This article covers how nattokinase interacts with warfarin, aspirin, and DOACs like Eliquis and Xarelto, what the research shows about bleeding risk, and how to have an informed conversation with your doctor. It is the anticoagulant-specific deep dive in our interactions series.

How Does Nattokinase Affect Blood Clotting?

Nattokinase is a serine protease enzyme with direct effects on the coagulation system, which sets it apart from most supplements. It works through two complementary mechanisms:

• Direct fibrinolysis: Nattokinase breaks down fibrin, the structural protein that forms the mesh of blood clots. This is its primary mechanism; it physically degrades existing fibrin strands (Chen et al., 2018).
• Plasminogen activation: Nattokinase also converts plasminogen to plasmin, the body's own clot-dissolving enzyme, which amplifies the fibrinolytic effect.

Clinical research has also shown that nattokinase decreases plasma levels of fibrinogen, factor VII, and factor VIII, key proteins in the clotting cascade (Hsia et al., 2009). These are the same markers physicians monitor when managing patients on anticoagulant therapy, which is exactly why the combination question matters.

Why Should You Avoid Combining Nattokinase and Blood Thinners?

The core issue is additive anticoagulation. Blood thinners already shift the body's clotting balance; nattokinase shifts it further in the same direction. Here’s how the most common medications overlap with nattokinase's mechanisms:

What Does the Research Say About Bleeding Risk?

The clinical evidence on nattokinase bleeding risk comes almost entirely from studies of nattokinase used alone, not in combination with blood thinners. That distinction shapes everything below.

Nattokinase Alone Has a Strong Safety Profile

In the largest nattokinase safety dataset available, 1,062 participants took 10,800 FU per day for 12 months with no serious adverse events reported (Chen et al., 2022). A single-dose study at 10,800 FU showed enhanced fibrinolytic activity and anticoagulant effects in healthy volunteers without adverse events (Kurosawa et al., 2015). An 8-week study in 45 participants found significant reductions in fibrinogen, factor VII, and factor VIII with no bleeding events reported (Hsia et al., 2009).

The Gap: No Large Studies on Nattokinase Plus Blood Thinners

Here’s the critical caveat: major nattokinase trials systematically excluded participants on anticoagulant therapy. We have strong evidence that nattokinase is safe on its own, and limited evidence on what happens in combination.

Case reports in the medical literature have documented instances of increased bleeding in patients who combined nattokinase with warfarin without medical supervision. Case reports are not controlled studies, but they reinforce the caution: the absence of evidence is not evidence of absence. Until studies specifically examine the combination, the medical consensus is to avoid combining them unsupervised.

Who Should Not Take Nattokinase Without a Doctor's Approval?

Based on current evidence, five groups should not take nattokinase without explicit physician approval:

1. People on anticoagulant medications: Warfarin, heparin, rivaroxaban, apixaban, dabigatran, or any other blood thinner. Your physician manages your anticoagulation carefully, and adding nattokinase without their knowledge can disrupt that balance.
2. People on antiplatelet therapy: Aspirin, clopidogrel, or similar. Nattokinase works through different mechanisms, but the additive effect on clot prevention may increase bleeding risk.
3. People with bleeding disorders: Hemophilia, von Willebrand disease, and other coagulopathies already impair clot formation; a fibrinolytic enzyme could worsen bleeding tendency.
4. People scheduled for surgery: Discontinue nattokinase at least two weeks before any scheduled procedure. Its fibrinolytic effects can persist for several days after the last dose.
5. Pregnant or nursing women: There is insufficient safety data for these populations.

For the full picture of nattokinase side effects and contraindications beyond blood thinners, see our overview.

How Should You Talk to Your Doctor About Nattokinase?

Do not stop or adjust any prescribed medication on your own. If you are on a blood thinner and interested in nattokinase, the decision belongs with the physician who manages your anticoagulation. Make the conversation productive by covering these points.

Here’s what to tell your doctor:

• What nattokinase is: a fibrinolytic enzyme derived from fermented soybeans (or chickpeas)
• The dose you are considering: the clinically studied dose is 10,800 FU per day (Chen et al., 2022)
• The mechanisms: direct fibrin degradation, plasminogen activation, and reduction of clotting factors VII and VIII
• Your motivation: circulation support, cholesterol support, blood pressure, or another specific goal

Ask your doctor questions like:

• Would my INR or other clotting markers need more frequent monitoring?
• Are there blood tests that could help assess the combination in my case?
• What signs of excess anticoagulation should I watch for?

What If You Are Not on Blood Thinners?

For people not on anticoagulant or antiplatelet therapy, the safety picture is much clearer. The Chen et al., 2022 study's 1,062 participants took 10,800 FU daily, co-administered with 180 mcg of Vitamin K2, for a full year with no serious adverse events, alongside significant improvements in lipid profiles and measures of arterial health. A lower dose of 3,600 FU per day was ineffective, demonstrating a clear dose-response relationship. Related trials have reported a 5.55 mmHg systolic blood pressure reduction (Kim et al., 2008) and a 36.6% reduction in carotid plaque size (Ren et al., 2017).

Toku Flow follows that same studied protocol: 10,800 FU nattokinase with 180 mcg Vitamin K2 (MK-7) per daily serving. As with any supplement, check with your healthcare provider before starting, especially if you take any medication.

The Bottom Line

Nattokinase on its own has one of the strongest safety records in the supplement world, backed by a 12-month study of over 1,000 participants. Combined with blood thinners, it is a different question, and one that current research has not answered. If you take warfarin, aspirin, a DOAC, or any anticoagulant or antiplatelet medication, bring nattokinase up with your doctor before trying it, and never change your prescribed medication on your own.

*The information provided in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives. This content has not been evaluated by the Food and Drug Administration and is not intended to diagnose, treat, cure, or prevent any disease.

Sources:

1. Chen H, McGowan EM, Ren N, et al. Nattokinase: A Promising Alternative in Prevention and Treatment of Cardiovascular Diseases. Biomarker Insights. 2018;13:1177271918785130. https://pmc.ncbi.nlm.nih.gov/articles/PMC6043915/
2. Chen H, Chen J, Zhang F, et al. Effective management of atherosclerosis progress and hyperlipidemia with nattokinase: A clinical study with 1,062 participants. Frontiers in Cardiovascular Medicine. 2022;9:964977. https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2022.964977/full
3. Hsia CH, Shen MC, Lin JS, et al. Nattokinase decreases plasma levels of fibrinogen, factor VII, and factor VIII in human subjects. Nutrition Research. 2009;29(3):190-196. linkinghub.elsevier.com/retrieve/pii/S0271531709000220
4. Jensen GS, Lenninger M, Ero MP, Benson KF. Consumption of nattokinase is associated with reduced blood pressure and von Willebrand factor. Integrated Blood Pressure Control. 2016;9:95-104. https://www.dovepress.com/consumption-of-nattokinase-is-associated-with-reduced-blood-pressure-a-peer-reviewed-fulltext-article-IBPC
5. Kim JY, Gum SN, Paik JK, et al. Effects of nattokinase on blood pressure: a randomized, controlled trial. Hypertension Research. 2008;31(8):1583-1588. https://www.nature.com/articles/hr2008203
6. Kurosawa Y, Nirengi S, Homma T, et al. A single-dose of oral nattokinase potentiates thrombolysis and anti-coagulation profiles. Scientific Reports. 2015;5:11601. https://pmc.ncbi.nlm.nih.gov/articles/PMC4479826/
7. Ren NN, Chen HJ, Li Y, et al. A clinical study on the effect of nattokinase on carotid artery atherosclerosis and hyperlipidaemia. Zhonghua Yi Xue Za Zhi. 2017;97(26):2038-2042. https://pubmed.ncbi.nlm.nih.gov/28763875