Learn all about warfarin including how it works, side effects, vitamin K interactions and the importance of taking it as prescribed. VKA use is challenging because the therapeutic range is narrow and dosing is affected by many factors including genetic variation, drug interactions, and diet. Bleeding risk is higher with warfarin than direct oral anticoagulants (DOACs). Warfarin is used to prevent or treat blood clots, including deep venous thrombosis or pulmonary embolism. It is also used for blood clots that may be caused by certain heart conditions, open-heart surgery, or after a heart attack. Warfarin (Jantoven) is a medicine to prevent blood clots. It may save your life if you've had blood clots or are at risk of them. But warfarin can sometimes cause serious side effects, such as heavy bleeding. It's important to have regular health checkups if you take the medicine. Warfarin reduces the formation of blood clots. Warfarin is used to treat or prevent blood clots in veins or arteries, which can reduce the risk of stroke, heart attack, or other serious conditions. Warfarin may also be used for purposes not listed in this medication guide. Warfarin reduces the formation of blood clots. Coumadin is used to treat or prevent blood clots in veins or arteries, which can reduce the risk of stroke, heart attack, or other serious conditions. Coumadin may also be used for purposes not listed in this medication guide. The recommendations in this guide are based on the American Society of Hematology 2018 Guidelines for Management of Venous Thromboembolism: Optimal Management of Anticoagulation Therapy Warfarin (Coumadin® and Jantoven®) is an anticoagulant medication or “blood thinner” you take to prevent and treat blood clots that can lead to a stroke or heart attack. Warfarin slows down your blood’s ability to clot. Warfarin is prescribed for people who are at increased risk for developing harmful blood clots. This includes people with a mechanical heart valve, an irregular heart rhythm called atrial fibrillation, and certain clotting disorders such as antiphospholipid syndrome. The use of warfarin is declining with preference now being given to direct oral anticoagulants (DOACs) as first-line therapy in common anticoagulation indications, such as VTE treatment and prevention of recurrence, and stroke prevention in non-valvular atrial fibrillation (NVAF).