(800) 973-1540

Atrial Fibrillation (A-fib) and Blood Thinners

Choosing which anticoagulant is best to manage A-fib depends on stroke risk, bleeding risk, and other factors.

By , Caring.com senior medical editor
100% helpful
Happy senior couple planning household financials

Most people with atrial fibrillation (commonly called A-fib) end up taking some kind of blood-thinning medication on a regular basis. That's because A-fib can substantially increase the chance of developing a blood clot in the heart; if such a clot gets swept out of the heart and into the brain, it can cause a devastating stroke.

Taking an anticoagulant medication such as warfarin or dabigatran can reduce the chance of stroke by 50 to 70 percent. Aspirin can also be used, although it's less effective in bringing down stroke risk. But these medications also cause increased risk of bleeding (most commonly in the stomach and bowel) and can impose other burdens, such as the need for frequent monitoring.

For these reasons, deciding which blood thinner to use (if any) can be a tricky decision for both doctors and patients to make. Together, doctor and patient need to balance the risk of stroke versus the risk of bleeding.

Here are the key considerations that go into the decision, along with the four main options you'll likely be considering:

Key considerations

  • An individualized assessment of stroke risk (see FAQ: What's my risk of stroke from atrial fibrillation?). People with very low stroke risk can opt to take aspirin or even no stroke-preventing medication. For all other people with atrial fibrillation, experts usually recommend an anticoagulant such as warfarin or dabigatran.

  • Whether the person is at particularly high risk for bleeding caused by anticoagulants (see FAQ: What's my risk of bleeding caused by my blood thinner?). People at very high risk for bleeding may be better off taking aspirin instead of a stronger anticoagulant.

  • Whether the person fears strokes more than major bleeding or vice versa.

  • Individual circumstances, such as insurance coverage of medications, the number of other medications being taken, and the ability to keep up with frequent blood checks and dosing changes (if warfarin is being considered).

4 main blood-thinning options


First approved for anticoagulation in 1954, warfarin (brand name Coumadin) is the most commonly prescribed blood thinner. Warfarin works by blocking the action of vitamin K, which the body's liver uses to make certain clotting factors.

Pros: Inexpensive, well known to medical community, requires just once-daily dosing, and its blood-thinning effect can be reversed in the hospital, if necessary (following a bleeding complication or to prepare for surgery, for example) by giving intravenous Vitamin K.

Cons: Requires frequent monitoring to make sure blood isn't thinned too much or too little. Effect can be affected by a change in consumption of leafy greens (which contain vitamin K). Interacts with many commonly used medications. Some people need to take different doses on different days of the week, which can require extra attention. Warfarin is regularly included on lists of top-ten drugs causing emergency room visits, hospitalizations, and serious medical complications.

Best for: People who are at more than very low stroke risk, who aren't on many other medications, or who need an inexpensive medication and aren't at high bleeding risk.