Factor V Leiden (rs6025 or F5 p.R506Q[1]) is a variant (mutated form) of human factor V (one of several substances that helps blood clot), which causes an increase in blood clotting (hypercoagulability). “Coagulation factor V” is the name of a protein that helps your blood clot when needed, like after an injury. Your F5 gene tells your body how to make this protein. Factor V (Factor 5) is a protein in your blood that helps form clots when you’re injured. It’s produced primarily by liver cells and plays a central role in the clotting cascade, the chain reaction your body triggers to stop bleeding. An overview of symptoms, genetics, and treatments to help you understand factor V deficiency. Factor V (FV) deficiency was first described in a Norwegian patient in 1943 and reported by Dr. Paul Owren in 1947. Its incidence is about 1 in 1 million; fewer than 200 cases have been documented worldwide. Factor V is an essential blood-clotting protein that plays a supporting but critical role in normal coagulation. It is also known as Proaccelerin or Labile Factor. When Factor V levels or activity are reduced, the clotting process becomes inefficient, and bleeding may last longer than expected. Coagulation factor V (Factor V), also less commonly known as proaccelerin or labile factor, is a protein involved in coagulation, encoded, in humans, by F5 gene. [5] Factor V, or proaccelerin, is a protein made in your liver that helps convert prothrombin into thrombin. This is an important step in the blood clotting process. If you don’t have enough factor V. Healthcare professionals most often prescribe blood-thinning medicines to treat people who get blood clots. People who have the factor V Leiden gene change but who have not had blood clots don't need this medicine. People who have factor V Leiden get either one copy or, rarely, two copies of the changed gene from their parents. Having one copy of the changed gene slightly raises the risk of getting blood clots. We’ll be taking a deep dive into Factor V Leiden, exploring what it is, who is at risk, and how it can be treated. Our goal is to help demystify this condition and provide a comprehensive guide to living with Factor V Leiden.