If you have some kinds of heart or blood vessel disease, or if you have poor blood flow to your brain, your doctor may recommend that you take a blood thinner. Blood thinners reduce the risk of heart attack and stroke by reducing the formation of blood clots in your arteries and veins. You may also take a blood thinner if you have

• An abnormal heart rhythm called atrial fibrillation
• Heart valve surgery
• Congenital heart defects

There are two main types of blood thinners. Anticoagulants, such as heparin or warfarin (also called Coumadin), work on chemical reactions in your body to lengthen the time it takes to form a blood clot. Antiplatelet drugs, such as aspirin, prevent blood cells called platelets from clumping together to form a clot.

When you take a blood thinner, follow directions carefully. Make sure that your healthcare provider knows all of the medicines and supplements you are using.