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A deep vein thrombosis (DVT) is a blood clot which forms in a deep vein. Blood clots that develop in a vein are also known as venous thrombosis. DVT usually occurs in a deep leg vein, a larger vein that runs through the muscles of the calf and the thigh.
It can cause pain and swelling in the leg and may lead to complications such as pulmonary embolism. This is a serious condition that occurs when a piece of blood clot breaks off into the bloodstream and blocks one of the blood vessels in the lungs.
In some cases, there may be no symptoms of DVT. If symptoms do occur they can include:
DVT usually (although not always) affects one leg. The pain may be worse when you bend your foot upward towards your knee.
Each year, DVT affects around 1 person in every 1,000 in the UK. Anyone can develop DVT, but it becomes more common over the age of 40. As well as age, there are also a number of other risk factors, including:
The combined contraceptive pill and hormone replacement therapy (HRT) both contain the female hormone oestrogen, which causes the blood to clot more easily. If you're taking either of these, your risk of developing DVT is slightly increased.