Though atrial fibrillation may not always cause problems, this common kind of irregular heartbeat is a major risk factor for dangerous blood clots. If a blood clot travels to your lungs, it can cause a pulmonary embolism. When a clot blocks blood flow to your brain, that causes a stroke. If your doctor thinks you may be at risk for a stroke, he or she may prescribe blood thinners.

What does atrial fibrillation have to do with blood thinners?

Atrial fibrillation causes the top chambers of the heart to beat out of sync with the bottom chambers. This can make it difficult for your heart to pump blood efficiently, allowing blood to pool in the arteries. That raises your chances of a blood clot. Blood thinners lower your risk of a stroke by preventing the blood from clotting. According to the U.S. Food and Drug Administration (FDA), taking blood thinners could reduce the risk of stroke in people with atrial fibrillation by 50 to 60 percent. Not every person with atrial fibrillation is convinced, though.

Why many people with atrial fibrillation don't take blood thinners

As with any drug, it's up to the individual and his or her doctor to determine whether the benefits of blood thinners outweigh the risks. The FDA says about half of all people with atrial fibrillation who would benefit from blood thinners don’t take them even if their doctors recommend it. There are a few theories about why this is. First, these drugs don't make you feel any better; they prevent—rather than treat—a health problem. Second, blood thinners raise the risk of bothersome or dangerous bleeding.

Many people who could benefit from blood thinners don’t take them.

While blood thinners keep harmful blood clots from forming in the body, they also make it difficult for blood to clot when it needs to, forming scabs if the body is injured. Simple minor injuries like paper cuts may bleed for a much longer time. Less often, larger injuries may not be able to stop bleeding without medical help. Blood thinners can also occasionally lead to serious internal bleeding.

How doctors determine if their patients should take blood thinners

Doctors consider numerous factors when deciding whether to put individuals on blood thinners. There are two tests that measure the risk of stroke versus the risk of bleeding. These tests take into account age and gender, as well as stroke, renal disease, liver disease, hypertension, alcohol and drug use, and diabetes history.

If your doctor suggests you take blood thinners but you're concerned about the potential side effects, talk it over. He or she can give you all the facts you need to make a good decision.