5 Facts About Factor V Leiden and Blood Clots
Factor V Leiden (FVL) is a genetic condition that increases the risk of dangerous blood clots, such as deep vein thrombosis (DVT) and pulmonary embolism (PE). Here are five essential facts everyone should know:
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What is Factor V Leiden?
FVL is a mutation of Factor V, a key protein in the blood clotting process. Once activated, the mutated version is harder for the body to deactivate, leading to a higher risk of excessive clot formation. -
Who has it?
About 5% of Caucasians carry one copy of the FVL mutation (inherited from one parent). It is far less common in other ethnicities. Around 0.02% of Caucasians carry two copies (one from each parent). -
What is the risk?
A person with one FVL copy has a 4 to 8 times higher risk of developing a clot. With two copies, the risk increases up to 80 times. Compared to a baseline 1 in 1000 yearly clot risk in the general population, FVL carriers face a 0.4–0.8% (one copy) or up to 8% (two copies) yearly risk. -
Other risk factors matter more with FVL
Situations like smoking, estrogen therapy, pregnancy, and recent surgery already raise clotting risk — but in FVL carriers, these factors compound the danger significantly. -
Lifelong treatment may be needed
If someone with FVL experiences more than one clot, lifelong anticoagulation therapy (blood thinners) is often recommended to prevent recurrence.
Marco A. Ramos, MD, CCDS
Board-Certified in Internal Medicine & Nephrology
Certified Clinical Documentation Specialist
