Your Resource for all Things Relating to Factor V Leiden

I have a family history of blood clots... Should I be tested?

A family history of blood clots can be a sign that those family members are carrying the Factor V Leiden genetic mutation.

It can also be an indication that you have Factor V Leiden and signal the likelihood that you could be at risk for developing a blood clot.

A study found that individuals with the Factor V Leiden mutation who had a first-degree relative with a history of thrombosis (blood clotting) had a 3-fold higher risk for a blood clot or venous thrombosis (VTE) than Factor V Leiden carriers with a negative family history. The risk increased to 18-fold in those with two or more symptomatic relatives. 

The current recommended testing guidelines relating to Factor V Leiden are as follows:


  • those who have venous thrombosis under the age of 50
  • those who have recurrent venous thrombosis
  • those who have a family history of venous thrombosis
  • female smokers who have suffered myocardial infarction under the age of 50
  • venous thrombosis in pregnant women or those taking oral contraceptives
  • some guidelines include women with recurrent pregnancy loss, unexplained severe preeclampsia, placental abruption as well as intrauterine fetal growth restriction

Thus, the current testing guidelines would recommend that you be tested given the family history of blood clots in a first-degree (related by blood) family member.

Even if none of the conditions above are true, you may want to still consider being tested if you feel Factor V Leiden could be a possibility. Testing for Factor V Leiden can be controversial so be sure and check out the Testing For Factor V Leiden page to review the arguments for and against being tested.


Ultimately, for those who do not fall within the current testing guidelines and testing is not recommended, deciding whether to be tested for Factor V Leiden is a personal decision.

As always, the American Factor V Leiden Association recommends that you consult with your healthcare professional or genetic counselor to help you in deciding whether to be tested. They can help you interpret the results, explain your risks should you test positive, and make any necessary changes to your plan of care if needed.


The test to see if you have Factor V Leiden is not intrusive and one that your healthcare professional can perform with a simple blood test or you can test for Factor V Leiden yourself via one of the “direct-to-consumer” DNA testing kits.


If you receive positive results for Factor V Leiden from a home DNA testing kit, we recommend that you contact your healthcare professional and genetic counselor and let them know as soon as possible. Together you can review the results and make any changes to your current plan of care.

The American Factor V Leiden Association is working hard to promote public awareness, provide education and be a resource for knowledge.

Our current program initiative on testing is aimed at improving testing guidelines by taking a common sense approach and looking at all variables related to the disorder.

We hope to publish an in-depth position statement on Factor V Leiden testing in the coming months.

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