Deep vein thrombosis (DVT) is a blood clot in one of the deep veins in the body. 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 when a piece of blood clot breaks off into the bloodstream and blocks one of the blood vessels in the lungs.
DVT and pulmonary embolism together are known as venous thromboembolism (VTE).
Who is at risk?
Each year, one in every 1,000 people in the UK is affected by DVT.
Anyone can develop it but it becomes more common with age. As well as age, risk factors include:
- previous venous thromboembolism
- a family history of thrombosis
- medical conditions such as cancer and heart failure
- inactivity (for example, after an operation)
- being overweight or obese
Warning signs
In some cases of DVT there may be no symptoms, but it is important to be aware of the signs and risk factors of thrombosis and see your GP as soon as possible if you think you may have a blood clot. DVT can cause pain, swelling and a heavy ache in your leg (see DVT - Symptoms for more information).
Avoiding DVT
There are several things you can do to help prevent DVT occurring, such as stopping smoking, losing weight if you are overweight and walking regularly to improve the circulation in your legs (see DVT - Prevention for more information).
There is no evidence that supports taking aspirin to reduce your risk of developing DVT.
Assessing risk
Surgery and some medical treatments can increase your risk of developing DVT. It is estimated that 25,000 people who are admitted to hospital die from preventable blood clots each year.
The Department of Health has made the prevention of DVT a priority across the NHS. All patients admitted to hospital should be assessed for their risk of developing a blood clot and, if necessary, given preventative treatment.
This recommendation was made by the National Institute for Health and Clinical Excellence (NICE) in January 2010. For more information, read NICE's 2010 guidelines on Venous Thromboembolism - Reducing the Risk