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Limited evidenceHeart & metabolic

Nattokinase

Nattokinase is a fibrin-degrading enzyme from fermented soy with plausible mechanism and small positive trials, but the human evidence base is small, geographically narrow and short-term. The bleeding-risk questions are more concrete than the benefits.

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What the science says

  • Lowers blood pressure Limited evidence

    A randomised controlled trial in 86 adults with pre-hypertension found 2,000 FU/day for 8 weeks reduced systolic blood pressure by about 5.6 mmHg and diastolic by about 2.8 mmHg versus placebo. A 2023 systematic review and meta-analysis of nattokinase RCTs found similarly modest reductions, but the pooled trial count is small and nearly all trials come from East Asia with short follow-up.

  • Improves lipid profile Limited evidence

    Meta-analysed trials show small reductions in total cholesterol and LDL, but several of the positive studies combined nattokinase with red yeast rice or other actives, making the independent contribution of nattokinase impossible to isolate.

  • Fibrinolytic and anti-thrombotic activity Limited evidence

    Nattokinase demonstrably degrades fibrin in vitro and modestly alters fibrinolytic markers such as D-dimer and euglobulin lysis time after oral dosing. Whether an orally administered protease survives digestion in quantities sufficient to affect clinically meaningful thrombosis remains unresolved — there are no trials with clot or stroke endpoints of adequate size and quality.

  • Reduces carotid plaque Limited evidence

    A single trial reported reduced carotid intima-media thickness and plaque size over 6-12 months. It has not been independently replicated, and imaging-based endpoints in unblinded or single-centre settings are easily overstated.

Dosage & safety

Studied doseTrials used 2,000-4,000 FU/day (fibrinolytic units) — commonly 100-200 mg of extract standardised to 2,000 FU per 100 mg — taken once daily, often in the evening, for 8 weeks to 6 months. Note that FU, not milligrams, is the meaningful unit; products labelled only in mg are uninformative. Natto food itself contains vitamin K2 (MK-7), whereas most supplements are vitamin K-depleted; check which one you have.
SafetyThe main concern is bleeding. Because nattokinase has fibrinolytic activity, it should not be combined with warfarin, DOACs, heparin, aspirin or clopidogrel without medical supervision, and should be stopped at least 2 weeks before surgery or dental extraction. Case reports of intracerebral haemorrhage in users on antiplatelet therapy exist. Avoid in people with active bleeding, peptic ulcer, recent stroke or bleeding disorders. Soy-allergic individuals should avoid it. Some products retain vitamin K2, which would antagonise warfarin in the opposite direction — an unpredictable combination. Avoid in pregnancy and breastfeeding. Long-term safety data beyond 6 months are lacking.

How to take it

TimingOnce daily, commonly in the evening, as used in the trials.
With food?With or without food; take it with a meal if it causes nausea.
Worth knowingStop at least two weeks before any surgery or dental extraction, and dose by fibrinolytic units rather than milligrams.

Interactions

With medications

  • warfarin, DOACs and heparin

    Nattokinase is fibrinolytic, so it adds to anticoagulation and bleeding risk. do not combine without medical supervision

  • aspirin and clopidogrel

    Additive bleeding risk; a cerebellar haemorrhage has been reported in a patient combining nattokinase with aspirin. do not combine without medical supervision

  • blood-pressure medication

    Nattokinase lowers blood pressure modestly, which adds to antihypertensive drugs. monitor blood pressure when starting

With other supplements

  • fish oil, garlic, ginkgo and other antiplatelet supplements

    Additive effect on bleeding time. avoid stacking several of them, and stop all before surgery

  • vitamin K2 (MK-7)

    Some nattokinase products retain vitamin K2, which pulls in the opposite direction to warfarin while the enzyme pulls with it. check whether your product is vitamin K-depleted if you take warfarin

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does nattokinase lower blood pressure?

The evidence is limited: one trial in 86 adults with pre-hypertension found 2,000 FU/day for 8 weeks lowered systolic pressure by about 5.6 mmHg, and a meta-analysis found similarly modest effects. Nearly all trials are small, short and from East Asia.

Does nattokinase dissolve blood clots or plaque?

Nattokinase degrades fibrin in the lab, but it is unresolved whether enough survives digestion to matter, and there are no adequate trials with clot or stroke endpoints. A single unreplicated trial reported reduced carotid plaque.

Is nattokinase safe with blood thinners?

No: nattokinase is fibrinolytic and should not be combined with warfarin, DOACs, heparin, aspirin or clopidogrel without medical supervision; a brain haemorrhage has been reported with aspirin. Stop it at least 2 weeks before surgery or dental extraction.

How much nattokinase should I take?

Nattokinase trials used 2,000-4,000 FU/day, taken once daily for 8 weeks to 6 months. Dose by fibrinolytic units (FU), not milligrams, and if you take warfarin check whether the product is vitamin K-depleted.

Scientific references

Where to buy

Nutricost, Nattokinase, 100 mg (2,000 FU), 120 Capsules

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