Doctors generally use blood-thinning (anticoagulant) medications, such as warfarin (Coumadin, Jantoven), heparin or low molecular weight heparin to treat people who develop blood clots.
If genetic tests have confirmed that you have factor V Leiden, but you haven't had any blood clots, then your doctor probably won't prescribe blood thinners on a regular basis. But you may be given a course of blood thinners to reduce your risk of DVT during high-risk situations, such as having surgery or being hospitalized.
If you have a blood clot, standard initial treatment involves a combination of heparin and warfarin. Your doctor will discontinue the heparin after the initial treatment and continue the warfarin. How long you need to take medication will depend on the circumstances of your thrombosis.