My father has been taking this medication for over two years and about 18 months ago he experienced loss of blood in his stools and ended up in hospital with a stomach ulcer. He was told not to take warfarin for a while, however he was put back on it again and is experiencing stomach upset and diarrohea which concerns me that he may end up with a stomach ulcer again. The hospital have said that there is no proof that this medication causes these upsets but think it does.