How does nattokinase work in the body?

Nattokinase works by breaking down fibrin, a protein involved in blood clotting. As a potent fibrinolytic enzyme produced by Bacillus subtilis natto, it dissolves existing clots and prevents the formation of new ones by directly cleaving fibrin strands and enhancing the body's production of plasmin. This mechanism helps improve blood viscosity and circulation, supporting overall cardiovascular health. (Evidence Level: C)

Can you take nattokinase with blood thinners like warfarin?

You should not take nattokinase if you are on prescription blood thinners like warfarin, aspirin, or clopidogrel. Because nattokinase has significant blood-thinning and fibrinolytic properties, combining it with anticoagulant medications increases the risk of severe bleeding complications, such as internal hemorrhage or easy bruising. Always consult a physician before combining these supplements. (Evidence Level: C)

What is the recommended dosage for nattokinase?

The standard adult dosage for nattokinase is typically 2,000 to 4,000 fibrinolysis units (FU) per day. This dosage is often taken in divided doses or as a single daily capsule on an empty stomach to maximize absorption into the bloodstream. Dosage may vary based on the specific product concentration and individual health goals regarding cardiovascular support. (Evidence Level: C)

Is nattokinase safe to take during pregnancy?

Nattokinase is considered unsafe during pregnancy and breastfeeding. Due to its ability to break down fibrin and thin the blood, there is an increased risk of bleeding complications, which can be dangerous during delivery. Additionally, nattokinase is derived from fermented soybeans, posing a potential risk for those with soy allergies. Pregnant women should avoid this supplement. (Evidence Level: D)

What are the common side effects of nattokinase?

Common side effects of nattokinase are generally mild but related to its blood-thinning properties. Users may experience easy bruising, nosebleeds, or minor digestive upset. In rare cases, excessive bleeding may occur, particularly if taken alongside other anticoagulants. Individuals with soy allergies should avoid this supplement as it is derived from fermented soybeans. (Evidence Level: C)

Nattokinase Source (Bacillus subtilis natto)

PubMed-compiled information sheet

This sheet was compiled from PubMed (NIH) abstracts using AI assistance. Every factual claim is cited to a real PubMed article (see the source list). It has not yet been human-reviewed — confirm with a healthcare provider before use.

Compiled from 30 PubMed articles · model: gemma4:31b

Summary

Nattokinase is a serine protease produced by Bacillus subtilis natto, primarily recognized for its direct fibrinolytic activity [PMID:25348469, PMID:39404094].

Background

Nattokinase (NK), also known as subtilisin NAT, is an extracellular enzyme produced by the spore-forming bacterium Bacillus subtilis natto, which is used to create the traditional Japanese fermented soybean food known as natto [PMID:25348469, PMID:37840737].

Traditional uses

Natto is a traditional Japanese fermented food linked to beneficial health effects, including the prevention of high blood pressure, osteoporosis, and cardiovascular-associated disease [PMID:37840737].

Active compounds

The primary active compound is nattokinase, a subtilisin family serine protease [PMID:25348469, PMID:36517353]. Other components associated with B. subtilis natto include polygamma glutamic acid (PGA), menaquinone-7 (vitamin K2), and various bioactive peptides [PMID:36517353, PMID:39244358, PMID:35483288].

Mechanism of action

Nattokinase exerts direct fibrinolytic and antithrombotic activity [PMID:25348469, PMID:39404094]. It is a serine protease that can dissolve whole blood and euglobulin clots [PMID:34285859]. Additionally, it may mitigate molecular pathways related to inflammation and oxidative stress [PMID:39404094].

Clinical evidence

Evidence CThrombolysis/Fibrinolysis

Nattokinase demonstrates strong fibrinolytic activity and is stable enough in the gastrointestinal tract for oral thrombolytic therapy [PMID:25348469, PMID:34285859].

Evidence DAtherosclerosis

In a murine model, B. subtilis natto NTU-18 administration significantly reduced aortic lesion area by modulating peripheral immune cell alterations [PMID:41105179].

Evidence DHypertension

Nattokinase is attributed to the treatment of hypertension [PMID:25348469]; additionally, B. subtilis-fermented pigeon pea extracts significantly improved systolic blood pressure in an animal model [PMID:28911492].

Evidence DViral Infection

Natto extract inhibited SARS-CoV-2 and BHV-1 infections in vitro by proteolytically degrading the SARS-CoV-2 receptor-binding domain and BHV-1 glycoprotein D [PMID:34271432]. It also impaired Aujeszky's disease virus infection in cell culture and mice [PMID:37815203].

Evidence DObesity-related Inflammation

In obese rats, B. subtilis natto JLCC513 decreased body weight, reduced inflammation, and increased intestinal barrier function by inhibiting the TLR4/NF-κB/NLRP3 pathway [PMID:36036228].

Evidence summary

The evidence consists primarily of in vitro studies, animal models, and narrative reviews. While fibrinolytic activity is well-documented, most systemic health claims are based on preclinical data (Level D) or general reviews (Level C).

PubMed sources

1.PMID: 25348469 (2014) — Nattokinase: production and application. · Applied microbiology and biotechnology
2.PMID: 41105179 (2025) — Bacillus subtilis natto NTU-18 attenuates atherosclerosis progression by modulating peripheral immune cell alterations. · Applied microbiology and biotechnology
3.PMID: 36517353 (2023) — Nattokinase (Bac s 1), a subtilisin family serine protease, is a novel allergen contained in the traditional Japanese fermented food natto. · Allergology international : official journal of the Japanese Society of Allergology
4.PMID: 37840737 (2023) — Probiotic properties of Bacillus subtilis DG101 isolated from the traditional Japanese fermented food nattō. · Frontiers in microbiology
5.PMID: 33563053

Nattokinase Source

Sources & Citations