When an injury occurs that causes bleeding, a blood clot forms to stop the bleeding. When the injured blood vessel has healed itself, the clot is no longer needed and is gradually reabsorbed by the body. Substances in the blood (clotting factors) work to ensure that the blood flows freely and clots only when necessary.

In some situations, the body becomes more prone to developing blood clots abnormally, leading to clots in areas that can cause harm — the heart, lungs, brain or extremities. This can cause a blockage in circulation and hinder blood flow.

Patients at high risk for developing a blood clot can be prescribed warfarin or Coumadin to prevent the formation of a blood clot. Medical conditions that may require the use of warfarin or Coumadin include deep vein thrombosis, pulmonary embolism, atrial fibrillation, artificial heart valves and hereditary blood disorders.