nattokinase

Interested to hear from people who've tried Nattokinase (and Serrapeptase/Lumbrokinase). I'm currently trying Nattokinase. I jumped rather quickly up to 6000FUs and feel rough, but not sure if it's that or just PEM. But I'm wondering how long to try it for? What were your experiences with it?

My doctor recommended Nattokinase (by NuMedica) , this is in connection with TOS. Apparently it helps blood flow. Anyone here got any benefit from this supplement? There are a few brands out there, my doctor seemed to be keen on NuMedica as she rates their standards... but there are other brands.