Nattokinase
Also known as: Nattokinase, Natto Kinase, NK, Subtilisin NAT
Fibrinolytic enzyme from fermented soybeans, used where androgens have thickened the blood — a supportive measure, not a substitute for lowering hematocrit.
Substance family
Medications for blood pressure, lipids and glucose. They appear here because these are exactly the markers most anabolic compounds push in the wrong direction.
Effects on
Which outcomes this substance acts on — descriptive, not a recommendation.
Strain profile
Where this substance is most likely to hit — a rough orientation, individually dependent on dose, duration and predisposition.
This substance works against
Dosing & protocols by goal
Rough orientation ranges as reported in harm-reduction literature — not an individual treatment plan. Doses are individual and open-ended; frequency depends on the ester or half-life.
Alongside androgen use with rising hematocrit
IntermediateDose
2000–4000 FU / day
Frequency
1× daily, away from meals
Cycle length
For the duration of the cycle
Dosed in fibrinolytic units (FU), not milligrams — a product labelled only in mg says nothing about its activity.
General cardiovascular support
BasicDose
2000 FU / day
Frequency
1× daily
Cycle length
Ongoing
Studied for blood pressure and fibrinogen with modest effect sizes.
Side effect & countermeasure
Typical problems and what you can do to reduce harm — at a glance. Does not replace medical monitoring.
Problem
Used as a substitute for actually lowering hematocrit
Countermeasure
This is the important limitation. Nattokinase influences fibrin and clot breakdown — it does not reduce the number of red blood cells. A hematocrithematocritThe percentage of blood made up of red cells — rises on androgens and thickens the blood. above roughly 54 percent needs donation, a dose reduction or stopping, not an enzyme. Treating it as a fix removes the pressure to act on the actual number.
Problem
Additive effect with anticoagulants
Problem
Discontinuation before surgery
Countermeasure
Stop at least two weeks before any planned operation or dental procedure and tell the treating physician — the fibrinolytic effect is relevant to surgical bleeding.
Problem
Wide variation in product potency
Countermeasure
Activity is measured in FU, and products vary considerably. A capsule labelled '100 mg nattokinase' without an FU figure gives no usable information about dose.
Problem
Vitamin K2 content in some preparations
Countermeasure
Natto naturally contains vitamin K2, which opposes anticoagulants. Preparations differ in whether it has been removed — relevant for anyone taking warfarin.
Overview
Nattokinase is an enzyme isolated from natto, a traditional Japanese fermented soybean food. It has been studied for its fibrinolytic properties — its ability to break down fibrin, the protein that forms the structural mesh of a blood clot.
In this field it appears in a specific situation: androgens raise red blood cell production, blood becomes thicker, and the cardiovascular risk that comes with that is one of the more serious consequences of long-term use.
Mechanism of Action
Blood clotting and clot breakdown are a continuous balance. Fibrin forms the mesh that holds a clot together; plasmin breaks it down. Nattokinase acts on this side of the balance — it degrades fibrin directly and increases the activity of the body's own fibrinolytic system.
The practical consequence is a modest reduction in clot formation tendency and, in some studies, in blood pressure and fibrinogen levels.
What it does not do matters more here. Androgens raise hematocrit by increasing erythropoiesis — more red blood cells are produced. That is a different problem from fibrin. Blood that is thick because it contains too many cells does not become thinner because clot breakdown is enhanced.
This distinction is the reason nattokinase belongs in the supporting cast rather than the solution. If hematocrit climbs above roughly fifty-four percent, the measures that work are donating blood, reducing the dose or stopping the compound. An enzyme that improves fibrinolysis addresses a related but separate risk.
Typical Context
Nattokinase is taken at two to four thousand fibrinolytic units daily, away from meals, for the duration of a cycle in which hematocrit is a known issue — particularly with boldenone, testosterone at higher doses, or oxymetholone.
The dosing unit deserves attention because it is a common source of confusion. Activity is measured in FU, not milligrams. Two products both labelled "100 mg" can differ several-fold in actual enzymatic activity, and a label without an FU figure is not usable for dosing.
Anyone with surgery planned should stop at least two weeks beforehand and mention it — the effect on clot formation is real enough to matter in a surgical context.
Side Effects & Risks
- Increased bleeding tendency, particularly combined with anticoagulants
- Digestive upset
- Rarely: headache, low blood pressure
- Soy allergy is a contraindication
- Well tolerated overall
Blood Work & Monitoring
- Hematocrit & hemoglobin — the actual marker of the problem nattokinase is often expected to solve
- Blood pressure — measured at home
- Coagulation values (INR, aPTT) — relevant for anyone on anticoagulant therapy
Harm-Reduction Notes
- It does not lower hematocrit — donation, dose reduction or stopping are what work there
- Buy by FU, not by milligrams; mg labelling alone is meaningless
- Stop at least 2 weeks before surgery or dental procedures and inform the treating physician
- Discuss with a doctor before combining with anticoagulants; the effects add
- Not a reason to tolerate a hematocrit that is already too high
Legal status by region
Regulation differs considerably between jurisdictions and changes over time. This is a rough orientation, not legal advice — check the rules that apply where you are.
| Region | Regulatory status |
|---|---|
| United States | Dietary supplement |
| EU / UK | Food supplementHealth claims are restricted; sold without a therapeutic indication. |
| Most other jurisdictions | Freely available |
| Competitive sport | Not prohibited |