Nattokinase
Best for
Improve clot breakdown
Faint early signal 1 study, n=24 #1 of 4 studied
- 7 papers
- 1 of 29 outcomes
- 1 positive
- 1 severe, 4 major interactions
Nattokinase shows a faint early signal for normal clot breakdown in humans, while evidence remains too limited and short-term to establish a proven clinical benefit.
Risk, worst reported severity
- cerebellar hemorrhage (intracerebral hemorrhage) severe
- pulmonary haemorrhage
- heparin (unfractionated and related GAGs) major
- fondaparinux major
What nattokinase actually does
The body needs to clear blood clots after they have done their job. 26109079
| Outcome | Effect | Evidence | Dose | Time | Rank |
|---|---|---|---|---|---|
| Early research 1 | |||||
| Improve clot breakdown Faint early signal The body needs to clear blood clots after they have done their job. | | 1 RCT 1 papers · n=24 | 2000 other | — | #1 /4 |
Effect tiers come from native-unit MCID where available, Cohen's d otherwise.
Dose, timing & forms
How much
The only consumer-relevant clot-breakdown signal comes from a small human study using a single 2,000 FU dose. It found short-term changes in fibrin-breakdown markers, not proof that nattokinase prevents harmful clots or delivers a lasting clinical benefit.1 Treat this as an early research protocol, not an established daily target.
When and how long
Research does not establish a best time of day, meal pairing, or long-term schedule for nattokinase. The key human clotting experiment examined changes after a single dose, so claims that you need to take it at bedtime, fasting, or on a particular routine run ahead of the evidence.1 More important than timing: do not add it casually if you use medicines that affect clotting.
Forms & standardisation
Look for a label that states enzyme activity in FU, rather than relying only on a milligram amount. The human study that drives the clot-breakdown discussion used 2,000 FU, but it does not establish that every product with that number produces the same result.1 Fermented-food natto and isolated nattokinase supplements are not interchangeable research formats.
Adverse events and drug interactions
Safety events
Drug interactions
What this is and how it works
- Across 1 study (n=24), nattokinase improved three clot-breakdown endpoints; no MCID threshold was established.1
- Seven papers reviewed here span 29 outcomes, with clot-breakdown evidence concentrated in one small human study.
- Short-term findings do not establish nattokinase as treatment for clotting conditions or a substitute for medical care.
Nattokinase is an enzyme made when Bacillus bacteria ferment soybeans into natto, the sticky Japanese food with a famously strong smell. Supplement makers isolate and concentrate the enzyme, then usually label its activity in fibrinolytic units, or FU.1
Fibrin works like the mesh in a temporary wound patch. Nattokinase appears to nudge fibrin-clearing activity, like loosening that mesh after its repair job ends, and a small human study found short-term shifts in fibrin-breakdown markers after one dose.1 That biological signal is real enough to study, but it does not yet show that the supplement reliably improves meaningful health outcomes.1
Bottom line
Nattokinase suits someone who understands that the clot-support story remains early and is willing to wait for stronger clinical research. It does not suit anyone looking to manage a clotting condition on their own, or anyone taking medicines that affect clotting without clinician guidance. The current human signal is small, short-term, and far from a proven health outcome.1
Common questions
Does nattokinase thin your blood?
Who should avoid nattokinase?
What does 2,000 FU mean on a nattokinase label?
Can nattokinase replace a prescribed blood thinner?
Sources
Sources
Generated August 27, 2026