Deep vein thrombosis (also known as DVT) is the formation of a blood clot ('thrombus') in a deep vein. It most commonly affects the veins in the leg.

DVT may be asymptomatic, but the classic symptoms of DVT include pain, swelling and redness of the leg.

DVT may form for a number of reasons. The most common reason for developing DVT is recent surgery or hospitalisation where you can't move around a lot and keep your blood flowing. Other reasons DVT may develop include other reasons for immobilisation, such as air travel. Smoking, obesity, some forms of hormone based contraception, and some infections can also increase the risk of DVT occurring.

The usual treatment for DVT is anticoagulation. You may initially be started on heparin while also taking warfarin. Usually, warfarin will be taken for 3 to 6 months to reduce the risk of further clots developing in the legs. If you have had a DVT or pulmonary embolism (PE) in the past you may need to stay on warfarin for longer than this.