Nattokinase has not been approved by the FDA, and contrary to claims on the internet, it should not take the place of an anticoagulant. While one study shows that a nattokinase supplement lowers the risk of blood clots after long plane flights, optimal doses of nattokinase have not been set for any condition. Quality and active ingredients in supplements may vary widely from maker to maker. This makes it very hard to set a standard dose. It is advised to steer clear of this product for now.