At Discount Prices Anticoagulants are used to treat and prevent blood clots that may occur in your blood vessels. Warfarin is the most commonly used anticoagulant. However, newer anticoagulants are now available and are likely to be used more and more. If you take warfarin you need to have regular blood tests to monitor how quickly your blood clots. The main possible side-effect of anticoagulants is bleeding. Warfarin interacts with some other medicines and foods. If you are prescribed or buy any other medicine then tell your doctor, nurse or pharmacist if you are taking an anticoagulant.