Your Resource for all Things Relating to Factor V Leiden

Most people have never heard of Factor V Leiden - even though it is the most common inherited risk factor for abnormal blood clotting in the United States.

The American Factor V Leiden Association

Unfortunately, many people are not aware they carry the Factor V Leiden gene until they or a family member develops an abnormal venous blood clot.

Although a simple blood test can detect Factor V Leiden, very few people are ever tested for the disorder until AFTER they have a blood clot.

Being unaware that you have the disorder puts you at risk for serious or fatal outcomes.

We are here to help

The American Factor V Leiden Association

If you have been diagnosed with Factor V Leiden, please know that you are not alone.  Millions of people around the world carry the Factor V Leiden genetic disorder.  The National Institutes of Health (NIH) estimate that approximately:



  • 10% of individuals with the Factor V Leiden mutation will develop abnormal blood clots.  Some of these blood clots can lead to long-term health problems or become life threatening.
  • Most of the remaining 90% will go through life never knowing they were at risk for abnormal blood clots nor are they aware they could have passed the genetic disorder on to their children.

Knowledge is Power… Our goal is to provide you and your family with a wealth of resources and information so that, while working closely with your healthcare professional, informed and intelligent medical decisions can be made in order to reduce your risk of developing venous blood clots related to Factor V Leiden.


The American Factor V Leiden Association is working to expand awareness, promote education, and encourage additional research to gain knowledge and pass that information on to you.

We want to help answer your questions.

  • To get started, check out the “Quick Links” page.
  • To get answers to the most common questions, visit the “What is Factor V Leiden” section.
  • For additional information about the disorder, check out the “Knowledge Resource Center” section.
  • In the coming months, you will have access to the “Research & Resource Library” section. There you will find information and studies covering over 220 in-depth topics in 10 categories all relating to Factor V Leiden.

Dr. John Bartholomew discusses Factor V Leiden.

Cleveland Clinic Section Head, Vascular Medicine and Director of the Thrombosis Center, Dr. John Bartholomew discusses Factor V Leiden.

Our Mission

We are on a mission to educate the world about Factor V Leiden.  The American Factor V Leiden Association is dedicated to its mission to serve as a central resource to the general public and medical community. Our goal is to expand awareness, promote education, advocate for and support those affected, assist in establishing testing guidelines, strongly encourage additional research, and facilitate in the exchange of information relating to Factor V Leiden.  The ultimate goal is to save lives that would have been lost to blood clots associated with Factor V Leiden.

Together through knowledge and awareness we can reduce the risk and help to improve and save lives.

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