Nattokinase: What It Is, Forms, Cautions, and Clean Brands

Nattokinase is an enzyme from natto, a fermented soybean dish. It supports healthy circulation.*

Forms and what to look for on the label

Activity measured in FU (fibrinolytic units), not just milligrams. NSK-SD is a branded, standardized ingredient.

Before you take it

It can affect blood clotting. Talk to your doctor if you take blood thinners or aspirin, or you have surgery coming up.

What independent doctors say

Dr. Peter McCullough has written about nattokinase at length on his Substack, The Focal Points. He is Chief Scientific Officer of The Wellness Company (TWC leadership page). The company sells products that contain nattokinase, which he discusses in his Oct 20, 2025 post.

“Out of all the available therapies I have used in my practice and among all the proposed detoxification agents, I believe nattokinase and related peptides hold the greatest promise for patients at this time.” (The Focal Points, Feb 21, 2023)

In the same post he wrote that “an empiric starting dose could be 2000 FU twice a day.” In an Aug 17, 2026 post, he listed “nattokinase >10,000 FU per day” and added: “All of these should be approved by the managing doctor and the individual risks including bleeding should be understood for the group.” (The Focal Points, Aug 17, 2026)

He has also written about the limits of the evidence:

“No therapeutic claims can be made since large, prospective, double-blind randomized, placebo-controlled trials have not been completed on any of the compounds mentioned in this paper.” (The Focal Points, Aug 25, 2023)

For more of his own words, see our article on why Dr. McCullough talks about nattokinase.