in fact, most people who have heterozygous
factor V Leiden never develop blood clots. Homozygous
factor V Leiden increases the risk of developing clots to a greater degree, about 25- to 50-fold. If you have the heterozygous form of factor V Leiden, the lifetime risk of developing a DVT is 10% or less, but may be higher if you have close family members who have had a DVT.