Nattokinase

Studies commonly use around 100–200 mg/day (about 2,000 fibrinolytic units, FU), on an empty stomach. Evidence is limited and early. Because it may affect clotting, avoid it with blood thinners or before surgery unless a clinician approves.

Nattokinase is an enzyme extracted from natto (fermented soybeans). It is measured in fibrinolytic units (FU), NOT milligrams: across the randomised trials in a 2023 systematic review the daily dose ranged from 1,200 to 8,000 FU, with 2,000 FU/day the most commonly used. Pooling six trials in 546 participants, the review found nattokinase significantly reduced systolic blood pressure (mean difference −3.45 mmHg) and diastolic blood pressure (−2.32 mmHg) versus placebo, with no significant benefit for blood lipids or glucose. The authors state plainly that "the total number of studies examining any cardiovascular risk factor was small, so these findings should be interpreted cautiously." — per a systematic review in NIH PMC.

In the six trials that recorded adverse events, "no notable adverse events were reported in all studies due to intake of nattokinase." The bleeding caution you see on labels is mechanism-based rather than trial-based: nattokinase works by hydrolysing fibrin directly, degrading PAI-1 and increasing tissue plasminogen activator — i.e. it increases fibrinolytic activity. Because of that mechanism, people on anticoagulant or antiplatelet drugs, people with bleeding disorders, and anyone scheduled for surgery should speak to a clinician before using it. This is general information, not medical advice. — per systematic and mechanistic reviews in NIH PMC; not medical advice.

No interaction trials exist. On mechanism alone — nattokinase raises fibrinolytic activity — combining it with anticoagulants or antiplatelets (warfarin, aspirin, clopidogrel) is a theoretical bleeding risk that a clinician should weigh, not a documented interaction. — per a mechanistic review in NIH PMC; not medical advice.