This exhibit shows the mechanism of blood clots and Coumadin including the associated benefits and risks of the medication. When clotting factors accumulate blood cells become trapped, forming a clot. A thrombus can then form, blocking blood flow. Coumadin is used to prevent the formation of these blood clots, allowing blood to flow freely within the circulatory system. However, excess coumadin can also cause hemorrhaging (uncontrolled bleeding).