I started using Nattokinase supplementation about a year ago after reading about it online in numerous articles are research docs on pubmed. I wanted to take something to prevent blood clots as heart disease and strokes runs in one side of my family. I think this is an amazing supplement, but wanted to warn that people it is extremely powerful (more so than aspirin) and people should always start off with a very low dose for at least a week. I consistently get a high pitched ringing in my one of my ears if I go off it and then start up on it. I like to take time off from all of my supplements, so I do this every week or so (take a few days off from supplements, that it). The high pitched EEEEEE happens once or twice after about 4 hours of taking nattokinase and then no more, but it always happens. I now take only 1/3 of a capsule per day. I pour open the capsules and pour 1/3 of the contents into a 1/2 cup of water and drink that down.
The other thing worth mentioning is to be very careful if you take nattokinase with Advil as it may cause blurry vision. I took an advil at night a few days ago to help with muscle stiffness and the next morning my vision was extremely blurry for the most of the day. Advil can cause blurry vision (one of the listed side effects), but I have never had that before. Worth noting. Would love to hear from other's experience. Can't find much about feedback from real people about nattokinase side effects on the web.