Natto Kinase is an alternative to Warfarin and I am now using it. I have had stomach upset and gas with Warfarin and do not trust most doctors anymore. I went to five doctors with pain and swelling in my left lower leg, and shortness of breath. I put the diagnosis in their pockets. I stated: "I'm on estrogen, couldn't this be a DVT?" Oh no, this is normal we women age. The US Health Care system is nothing more than about money. It is money-driven, not care-driven. The ultrasound was cheaper than the idiots I went to. I do not plan on staying on Warfarin and am delighted the Japanese can offer an alternative!!