Topic Overview

If you are at risk for developing a blood clot in your heart, you might take a blood thinning medicine, also called an anticoagulant. A blood thinner doesn't really thin your blood. It works by increasing the time it takes for blood clots to form. This medicine also keeps an existing clot from getting larger. An example of a blood thinner is warfarin.

Blood clots in the heart are a risk factor for the type of stroke that is caused by a small piece of the clot breaking off and traveling to the brain. Blood clots can also happen in your legs. If these blood clots move to your lungs, they can cause a life-threatening pulmonary embolism.

If you have heart failure, you might take warfarin if you:

• Have atrial fibrillation, an irregular heart rhythm which significantly increases the risk of forming a blood clot in your heart that can travel to the brain and cause a stroke.
• Have had a previous stroke caused by a blood clot from your heart.
• Have already had a blood clot in your heart or legs.

Some doctors also prescribe warfarin when the percentage of blood pumped out of the heart with each beat (ejection fraction) is very low, because the lower the ejection fraction, the higher your risk of forming a blood clot and having a stroke. But doctors do not agree on how low the ejection fraction needs to be to warrant warfarin therapy, and some doctors do not prescribe warfarin based on the ejection fraction alone.

Safety when you take blood thinners

Because warfarin slows the amount of time it takes for your blood to clot, you need to take extra steps avoid bleeding problems. These steps include:

• Get regular blood tests.
• Prevent falls and injuries.
• Eat a steady diet, and pay attention to foods that contain vitamin K.
• Tell your doctors about all other medicines and vitamins that you take.

For more information about safety, see:

Warfarin: Taking Your Medicine Safely.