Nattokinase: Uses, Benefits, Dosage & Safety

Last updated: June 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy

What is Nattokinase?

Nattokinase is an enzyme produced when soybeans are fermented with the bacterium Bacillus subtilis to make natto, a stringy, strongly flavoured Japanese food. In the laboratory, nattokinase can break down fibrin — the protein mesh that forms blood clots — which is the origin of its reputation as a 'clot-busting' supplement. Whether swallowing the enzyme produces meaningful clot-related effects inside the body is a separate and much less settled question, because enzymes are proteins that can be partly broken down during digestion.

What Nattokinase is commonly used for

In supplements, Nattokinase is taken mainly for cardiovascular and circulation support, blood-pressure support, and 'blood thinning' or clot-related concerns. It is sometimes combined with other heart-health ingredients such as red yeast rice. It is sold as nutritional support, not a treatment, and it should never be used as a substitute for prescribed blood thinners or blood-pressure medication.

How Nattokinase works

Nattokinase is a fibrinolytic enzyme, meaning that in lab conditions it can cleave fibrin and related proteins involved in clot formation, and it may influence other parts of the clotting and blood-pressure systems. The proposed benefits for circulation follow from this activity. The honest caveat is delivery: it is not fully established how much active enzyme survives digestion and reaches the bloodstream, so the mechanism that looks impressive in a test tube does not automatically translate into a strong effect in people.

What the evidence says

Here's an honest snapshot of what published research suggests about Nattokinase — including where the evidence is limited.

• A systematic review and meta-analysis of randomised controlled trials (546 participants) found nattokinase modestly lowered systolic and diastolic blood pressure versus placebo, with no clear benefit for blood lipids at the doses studied. (PubMed)
• General background on natto, nattokinase and its safety is summarised by reputable health references. (MedlinePlus)

Typical dosage used in studies

Nattokinase is dosed in fibrinolytic units (FU) rather than milligrams. Studies commonly use around 2,000 FU per day, sometimes split into two doses. Blood-pressure effects in trials build over several weeks. This is general information from research, not a recommendation — and because of its blood-thinning potential, it is one supplement where checking with a doctor first genuinely matters.

Side effects and safety

In trials, nattokinase has generally been well tolerated, with no serious side effects reported at the doses used. Because it comes from fermented soybeans, people with a soy allergy should be cautious, and severe allergic reactions have occasionally been described. The bigger concern is its theoretical effect on bleeding (below) rather than direct toxicity.

Medication interactions and who should avoid Nattokinase

Sources & further reading

The evidence summary above is drawn from these sources. For general, authoritative background you can also consult:

• PubMed-indexed study (PMID 39076715)
• MedlinePlus
• NIH Office of Dietary Supplements
• NIH National Center for Complementary and Integrative Health

Frequently asked questions

Does nattokinase actually lower blood pressure?

Pooled randomised trials suggest a modest reduction in systolic and diastolic blood pressure versus placebo. The effect is real but small, and nattokinase is a support, not a replacement for prescribed blood-pressure treatment.

Does nattokinase dissolve blood clots?

It breaks down fibrin in the laboratory, which is where the 'clot-busting' reputation comes from. Evidence that swallowing it meaningfully dissolves clots in people is not established, so these claims overstate the data.

Is nattokinase a natural blood thinner?

It has blood-thinning potential, which is exactly why it needs caution. It can add to prescription blood thinners and antiplatelet drugs and increase bleeding risk, so it should not be combined with them without medical advice.

What dose is used in studies?

Research typically uses about 2,000 fibrinolytic units (FU) per day. Nattokinase is measured in FU rather than milligrams, so comparing products by FU is more meaningful than by weight.

Who should avoid nattokinase?

Anyone on blood thinners or antiplatelet drugs, people with bleeding disorders, those about to have surgery, anyone with a soy allergy, and people who are pregnant or breastfeeding should avoid it or check with a doctor first.