My dad is 86 and has been living a good life despite having Parkinson s for many years. He also has been on coumadin for more years than I can count. My mother recently lost track of his coumadin and the summary of this is that his blood was so thin he nearly died. He is now in hospital with many problems. He has complained of stomach hurting every time he eats and there is blood in stools. Why the stomach hurting?