Nattokinase
Nattokinase is an enzyme from Japanese fermented soy (natto) that helps your body break down blood clots. It's one of the few natural fibrinolytic agents with real clinical evidence.
Nattokinase is a serine protease enzyme extracted from natto (fermented soybeans). It has direct fibrinolytic activity — meaning it helps dissolve fibrin, the protein that forms blood clots. It also lowers blood pressure and improves circulation.
Good for you if: You want to support cardiovascular health naturally, have a family history of blood clots, or have mildly elevated blood pressure.
Dive deeper into the researchCommon side effects
- Must not be combined with blood thinners (warfarin, aspirin)
- Increased bleeding risk if you bruise easily
- Stop 2 weeks before surgery
What does nattokinase do?
Your body naturally forms and dissolves blood clots all the time. The enzyme that dissolves clots is called plasmin. Nattokinase works in two ways: it directly breaks down fibrin (the structural protein in clots), and it also activates your body's own plasmin system — boosting your natural clot-dissolving ability.
Beyond clot dissolution, nattokinase has been shown to lower blood pressure (by inhibiting ACE, similar to prescription ACE inhibitors) and reduce blood viscosity.
What can you expect?
- Improved circulation — less blood viscosity, better flow
- Lower blood pressure — modest but consistent reductions (3–5 mmHg systolic)
- Clot prevention — enhanced fibrinolytic activity
- Reduced fibrinogen — lower levels of the clot-forming protein
How to take it
2,000 FU (fibrinolytic units) once daily, preferably in the evening or between meals. Some people take 2,000 FU twice daily for stronger cardiovascular support.
Look for products standardised to at least 2,000 FU per capsule. "NSK-SD" branded nattokinase has had vitamin K2 removed (important if you're concerned about clotting).
Do not take nattokinase if you're on blood thinners (warfarin, heparin, clopidogrel, or even daily aspirin) without your doctor's approval. The combination can cause dangerous bleeding. Stop nattokinase at least 2 weeks before any surgery.
Monitor your cardiovascular markers
eterni tracks your blood pressure, fibrinogen, and lipid panels over time to show you if nattokinase is making a difference.
Get early accessFrequently Asked Questions
Can I take nattokinase instead of aspirin for heart health?
Don't make this switch on your own. If your doctor has prescribed daily aspirin for a specific cardiac reason, you should not replace it with nattokinase without medical supervision. Nattokinase works through different mechanisms (fibrinolysis vs platelet inhibition). For people without a prescription anticoagulant need, nattokinase is a reasonable cardiovascular support supplement.
Does nattokinase contain vitamin K2?
Regular nattokinase may contain trace amounts of vitamin K2 from the natto fermentation process. If you're on warfarin (which works by blocking vitamin K), look for NSK-SD branded nattokinase, which has vitamin K2 specifically removed. For most people not on warfarin, the K2 content is actually a bonus.
How long does nattokinase stay active in the body?
Studies show nattokinase's fibrinolytic activity peaks about 2–4 hours after ingestion and remains elevated for up to 8–12 hours. This is why once or twice daily dosing is sufficient for maintaining its effects throughout the day.
Is nattokinase safe for long-term use?
Yes, for people who are not on anticoagulant medications. Long-term studies (up to 12 months) show consistent safety. Natto itself has been consumed daily in Japan for centuries. The main risk is combining it with other blood-thinning agents.
How nattokinase works
Nattokinase is a 275-amino acid serine protease produced by Bacillus subtilis natto during soybean fermentation. It has four distinct fibrinolytic mechanisms: direct hydrolysis of fibrin cross-links, conversion of prourokinase to urokinase, degradation of plasminogen activator inhibitor-1 (PAI-1), and direct activation of pro-urokinase. It also inhibits angiotensin-converting enzyme (ACE), producing a blood pressure-lowering effect similar to mild ACE inhibitors.
What the studies show
- Fibrinolysis: Single 2,000 FU dose increased fibrinolytic activity and D-dimer levels within 2–8 hours (human pharmacokinetic study)
- Blood pressure: Meta-analysis of 7 RCTs — nattokinase reduced systolic BP by 3.5 mmHg and diastolic by 2.1 mmHg
- Lipids: 26-week RCT — nattokinase reduced total cholesterol by 7.3% and LDL by 11.5% vs placebo
- Deep vein thrombosis: Nattokinase reduced DVT incidence in long-haul flight passengers in a small controlled trial
Side effects & safety
- Bleeding risk — The primary concern. Nattokinase enhances fibrinolysis, increasing bleeding time. Bruising may increase.
- Drug interactions — Dangerous with warfarin, heparin, clopidogrel, aspirin, and other anticoagulants/antiplatelets.
- Surgery — Stop at least 2 weeks before any planned surgery or dental procedure.
- Soy allergy — Nattokinase is derived from soy. Most allergenic proteins are degraded during fermentation, but caution is warranted in severe soy allergy.
Which labs to check
- Fibrinogen — the protein nattokinase targets; should decrease with use
- D-dimer — clot breakdown marker; may transiently increase (this is expected)
- Lipid panel — LDL and total cholesterol may modestly improve
- Blood pressure — track at home for 4–8 weeks
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