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decision pointShould I take anticoagulants to prevent stroke?

Anticoagulant medicine, such as warfarin (Coumadin, for example), is highly effective in preventing stroke and death due to stroke in people with atrial fibrillation. But it may not be suitable for everyone. Consider the following when making your decision:

  • Anticoagulant medicine, such as warfarin, provides the best protection against stroke, if you can take it.
  • Almost everyone who has atrial fibrillation should take warfarin. The only people with atrial fibrillation who may not benefit from taking warfarin are people with lone atrial fibrillation who are younger than 65 and have no other risk factors for stroke, or people with chronic kidney disease, recent surgery or head trauma, a history of gastrointestinal bleeding, or alcoholism.
  • If you are going to have cardioversion, your doctor will recommend that you take anticoagulant medicine for 3 weeks before and for at least 4 weeks after cardioversion, to reduce the risk of stroke.
  • If you have lone atrial fibrillation and are younger than 60, you can take 325 mg of aspirin daily instead of warfarin.
  • If you are at risk for a stroke, aspirin can help prevent a stroke. But aspirin does not work as well as warfarin.
  • When taking anticoagulants, you are required to have regular blood tests to assess your risk for problem bleeding.

What is an anticoagulant medicine?

Anticoagulants are medicines that help prevent blood clots. They are often called blood thinners, but they do not actually thin the blood. Instead, anticoagulants work by increasing the time it takes a blood clot to form.

Why is it important to take anticoagulant medicines?

Atrial fibrillation increases your risk of stroke. People with atrial fibrillation and an otherwise normal heart are 5 to 6 times more likely to have a stroke than people who do not have atrial fibrillation.1 People who have heart valve damage along with atrial fibrillation have an even higher risk. Taking anticoagulant medicines significantly reduces your risk. The most commonly used anticoagulants are warfarin and heparin.

What are the risks of taking anticoagulant medicines?

Anticoagulants slow the amount of time it takes for your blood to clot. This increases your risk of developing problems with bleeding within and around the brain, bleeding in the stomach and intestines, bruising and bleeding if injured, and serious skin rash.

You should not take anticoagulants if you:

  • Have unexplained blood in the stool.
  • Have uncontrolled high blood pressure.
  • Are at high risk for falling.
  • Are unable to take the medicine as directed.
  • Drink large amounts of alcohol.
  • Are unable or unwilling to have regular blood tests.

Women with atrial fibrillation who are pregnant or plan to become pregnant should talk with their doctor about the potential benefits and risks of taking anticoagulants. These women should not take warfarin (such as Coumadin) because it can cause birth defects. Use of some anticoagulants, such as heparin, may complicate pregnancy and childbirth and can increase the risk of developing osteoporosis or thrombocytopenia if taken over the long term.

How well do anticoagulants work?

Anticoagulants significantly reduce the risk of stroke in people who have atrial fibrillation.2 But how much your risk will be lowered depends on how high your risk was to start with. Not everyone with atrial fibrillation has the same risk of stroke. It's a good idea to talk with your doctor about your risk.

You will want to weigh the benefits of reducing your risk of stroke with the risks of taking anticoagulants. Warfarin works well to prevent stroke. But warfarin also increases the risk of bleeding. Each year about 2 out of 100 people who take warfarin will have a problem with severe bleeding, and 98 will not.3 But this is an average risk. Your own risk may be higher or lower than average based on your own health.

What can you do instead of taking anticoagulants?

Aspirin may be a good choice if you are young and have no other heart or health problems or if you can't take warfarin safely. Aspirin doesn't work as well as warfarin to reduce your stroke risk. But aspirin is less likely to cause bleeding problems.

If you are at low risk for stroke or can't take warfarin, your doctor may recommend that you take aspirin. Aspirin is an antiplatelet medicine. It decreases the risk of blood clotting by preventing the smallest blood cells (platelets) from sticking together and making a clot.

Aspirin lowers the risk of stroke in people with atrial fibrillation but not nearly as much as warfarin does. How much your risk will be reduced depends on how high your risk was to start with.

Aspirin is less likely than anticoagulants to cause bleeding problems. Bleeding that is bad enough to need treatment in a hospital happens in 1 or 2 out of 1,000 people who take aspirin.4 This means that 998 or 999 out of 1,000 people who take aspirin don't have serious bleeding.

Other antiplatelet medicines, such as clopidogrel (Plavix), may be used if you can't take aspirin.

For more information, see the topic Atrial Fibrillation.

Your choices are:

  • Take anticoagulants to reduce the risk of stroke.
  • Do not take anticoagulants-take aspirin instead.

The decision about whether to take anticoagulants takes into account your personal feelings and the medical facts.

Deciding about taking anticoagulants
Reasons to take anticoagulants Reasons not to take anticoagulants
  • Anticoagulants significantly reduce the risk of stroke and death from stroke.

Are there other reasons that you might want to take anticoagulants?

  • Anticoagulants have side effects, including problem bleeding, bruising, and skin rash.
  • You will need to have frequent blood tests to check the level of the anticoagulant in your blood.

Are there other reasons that you might not want to take anticoagulants?

These personal stories may help you make your decision.

Use this worksheet to help you make your decision. After completing it, you should have a better idea of how you feel about taking anticoagulants. Discuss the worksheet with your doctor.

Circle the answer that best applies to you.

I am at high risk for stroke. Yes No Unsure
I am not an alcoholic. Yes No Unsure
I am not comfortable having frequent blood tests. Yes No Unsure
I am older than 60, and I don't have lone atrial fibrillation. Yes No Unsure
I am going to have cardioversion for atrial fibrillation. Yes No Unsure
I am pregnant or plan to become pregnant. Yes No Unsure

Use the following space to list any other important concerns you have about this decision.






What is your overall impression?

Your answers in the above worksheet are meant to give you a general idea of where you stand on this decision. You may have one overriding reason to take or not to take anticoagulants.

Check the box below that represents your overall impression about your decision.

Leaning toward taking anticoagulants


Leaning toward NOT taking anticoagulants



  1. Wang TJ, et al. (2003). A risk score for predicting stroke or death in individuals with new-onset atrial fibrillation in the community: The Framingham heart study. JAMA, 290(8): 1049–1056.

  2. Hart R, et al. (2007). Meta-analysis: Antithrombotic therapy to prevent stroke in patients who have nonvalvular atrial fibrillation. Annals of Internal Medicine, 146: 857–867.

  3. Antiplatelet and anticoagulant drugs (2008). Treatment Guidelines From The Medical Letter, 6(69): 29–36.

  4. Patrono C, et al. (2008). Antiplatelet drugs: American College of Chest Physicians evidence-based clinical practice guidelines (8th edition). Chest, 133(6): 199S–233S.

Author Robin Parks, MS
Editor Kathleen M. Ariss, MS
Associate Editor Pat Truman, MATC
Primary Medical Reviewer Caroline S. Rhoads, MD - Internal Medicine
Specialist Medical Reviewer John M. Miller, MD - Electrophysiology
Last Updated December 18, 2008

WebMD Medical Reference from Healthwise

Last Updated: December 18, 2008
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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