What Does FU Mean in Nattokinase?

FU (fibrinolytic units) are a measure of nattokinase enzyme activity.

Basically, it's telling you how much activity potential the nattokinase has to breakdown and dissolve blood clots..

That distinction matters because enzymes are not adequately described by weight alone.

A milligram tells you:

how much weight the material has.

FU tells you:

how much measured enzyme activity is represented.

Why that matters on a supplement label

Two nattokinase preparations can contain similar amounts by weight while providing different measured enzyme activity.

That is why FU gives you a more useful way to understand nattokinase potency.

But there is another detail worth checking:

Is the FU amount per capsule or per serving?

A product advertising more than 10,000 FU may provide that amount in one capsule — or require multiple capsules.

That difference is dose density.  How much enzyme activity is packed into each capsule?

FU also helps you read the research

Human studies report nattokinase exposure using activity levels.

So, understanding FU lets you compare a product's labeled activity with the activity levels represented in published research.

FU tells you the activity.

It does not erase differences in formulation, delivery, study population or research design.

Takeaway

Milligrams tell you how much nattokinase weighs. FU tells you how much measured enzyme activity you are dealing with.

PB Natto

PB Natto is provisionally specified at 13,500 FU in one acid-resistant capsule, bringing activity and delivery together in a single-capsule formulation.