Blood thinners are medicines that prevent blood clots from forming. They also keep existing blood clots from getting larger. Clots in your arteries, veins, and heart can cause heart attacks, strokes, and blockages. You may take a blood thinner if you have
Certain heart or blood vessel diseases
An abnormal heart rhythm called atrial fibrillation
A heart valve replacement
A risk of blood clots after surgery
Congenital heart defects
There are two main types of blood thinners. Anticoagulants such as heparin or warfarin (also called Coumadin) slow down your body's process of making clots. 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. Blood thinners may interact with certain foods, medicines, vitamins, and alcohol. Make sure that your health care provider knows all of the medicines and supplements you are using. You will probably need regular blood tests to check how well your blood is clotting. It is important to make sure that you're taking enough medicine to prevent clots, but not so much that it causes bleeding.