Blood clots in the veins from the leg are a serious problem. When pieces of clot break off, the flow of blood carries them through the veins to the lungs, where they block the circulation to the lungs. The result is a pulmonary embolism, which can be fatal. Clots can also damage the leg veins, which can cause long-term leg discomfort and swelling. The treatment is anticoagulation (blood thinners), which interferes with normal blood clotting and gives the body's natural mechanisms a better chance to dissolve the clot. Anticoagulation greatly reduces the risk for death from pulmonary embolism, but it can cause severe, sometimes fatal, bleeding. Usually, patients receive anticoagulation for 6 months if they are having blood clots for the first time. After stopping anticoagulation, some patients may have another pulmonary embolism.