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At The Lab

Prevent Stroke with Anticoagulants


Many people with AFib need to take anticoagulants (sometimes called blood-thinners) to reduce the possibility of blood clots. Common reasons this type of medication may be prescribed include:

  • Heart rhythm disorders such as atrial fibrillation
  • Prior clots or clot risk
  • Previous stroke or warning stroke (TIA)
  • Prior heart attack or narrowed arteries
  • Certain congenital heart defects
  • Heart valve replacements


"Blood-thinning medicines" actually slow the blood’s ability to clot, which can help to prevent blood clots from developing and traveling to the brain, causing a stroke.

How are anticoagulants taken?


Anticoagulants are usually given by mouth. In some cases, such as in the hospital, they may be given by vein (intravenously) or injected just under the skin (subcutaneously).

Are there any common problems I should look for?
Bleeding may be a complication of taking these medications. Tell your doctor if you begin to bruise easily, or you notice unusual bleeding anywhere including gums or nose bleeds.

One type of anticoagulant, warfarin (Coumadin), requires lab work that may be done in an Anticoagulation Lab or may be done at home. The newer FDA approved anticoagulants, or novel oral anticoagulants ("NOACs"), such as dabigatran, rivaroxaban, apixaban and edoxaban generally do not require these regular lab tests to assess clotting time and thus will not be addressed in this section.

On the pages below, you’ll find tips and insight about:

  • What is Anticoagulation?
  • What you may want to understand about your labwork
  • How often you might need to visit a lab
At The Lab Articles
Understanding Warfarin

Warfarin: An Oral Anticoagulant Medication Warfarin (Coumadin) decreases the blood clotting tendency by interfering with blocking the body's blood clotting substances. There are other anticoagulants besides warfarin — your cardiologist will decide which one is right for you.

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Understanding Your Labwork

Getting started with monitoring If you are taking warfarin, your doctor will ask that you regularly monitor the blood-clotting level to be sure your medication is working and the dose of warfarin is correct. Your result is written as a value called the INR (international normalized ratio) tests how quickly your blood clots. Another test sometimes used is called the prothrombin time or PT. The INR is the most commonly done to test how warfarin is working.

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Learning the Basics of INR Management

A Patient's Guide to Taking Warfarin Warfarin (brand names Coumadin and Jantoven) is a prescription medication used to prevent harmful blood clots from forming or growing larger. Beneficial blood clots prevent or stop bleeding, but harmful blood clots can cause a heart attack, stroke, deep vein thrombosis or pulmonary embolism. Because warfarin interferes with the formation of blood clots, it is called an anticoagulant. Many people refer to anticoagulants as “blood thinners”; however, warfarin does not thin the blood but instead causes the blood to take longer to form a clot.

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