A Patient’s Guide to Taking Coumadin/Warfarin

W arfarin (brand names Coumadin and Jantoven) is a prescription medication used to prevent harmful blood clots from forming or growing larger.Beneficial blood clots prevent or stop bleeding, but harmful blood clots can cause a stroke, heart attack, deep vein thrombosis, or pulmonary embolism.Because warfarin interferes with the formation of blood clots, it is called an anticoagulant.Many people refer to anticoagulants as "blood thinners"; however, warfarin does not thin the blood but instead causes the blood to take longer to form a clot. How Does Warfarin Work?The formation of a clot in the body is a complex process that involves multiple substances called clotting factors.Warfarin decreases the body's ability to form blood clots by blocking the formation of vitamin K-dependent clotting factors.Vitamin K is needed to make clotting factors and prevent bleeding.Therefore, by giving a medication that blocks the clotting factors, your body can stop harmful clots from forming and prevent clots from getting larger.The information contained in this Circulation Cardiology Patient Page is not a substitute for medical advice, and the American Heart Association recommends consultation with your doctor or healthcare professional.