Menu Healthy Lifestyle Diseases & Conditions First Aid Symptoms Tests & Procedures Videos Definitions FAQs Factor V LeidenUpdated: 2017-06-13OverviewFactor V Leiden increases the chance of clumps of blood (clots) developing, which can be life-threatening. Women with the disorder risk developing blood clots during pregnancy or when taking the hormone estrogen. SymptomsMost people never develop symptoms. However, the first indication of the disorder may be the development of a blood clot (thrombosis). TreatmentsTreatment may include blood-thinning drugs. © 1998-2022 Mayo Foundation for Medical Education and Research(MFMER). All rights reserved. Terms of Use