Thrombosis is a blood clot within a blood vessel. It happens when a blood clot forms and blocks a vein or an artery, obstructing or stopping the flow of blood.
A blood clot can occur anywhere in the body’s bloodstream. There are two main types:
- venous thromboembolism (VTE), which is a blood clot that develops in a vein
- arterial thrombosis, which is a blood clot that develops in an artery
Venous thromboembolism (VTE)
One of the most common types of venous thromboembolism is deep vein thrombosis (DVT). This is a blood clot in one of the deep veins of the body, usually one of the larger veins in your leg. Read more about DVT.
Sometimes, part of a newly formed blood clot can come away from its original site and travel through the bloodstream. If this occurs, the clot can become lodged in another part of the body. A blood clot that lodges in one of the lungs is called a pulmonary embolism. Read more about pulmonary embolism.
The term venous thromboembolism (VTE) refers to both deep vein thrombosis (DVT) and pulmonary embolism.
Arterial thrombosis
Arterial thrombosis is usually associated with a condition called atherosclerosis, which causes narrowing of the arteries.
If a blood clot blocks the arteries leading to the heart and the blood supply to part of the heart is stopped, this is known as a heart attack. If a blood clot blocks an artery in the brain, this will cause a stroke.
Read more about arterial thrombosis.
Prevention
There are several things you can do to help prevent a blood clot.
Blood clots can be treated if they are spotted in time. However, preventing them from happening in the first place is often the preferred approach.
Making lifestyle changes, such as improving your diet, increasing the amount of exercise you do and stopping smoking if you smoke, can also help to significantly lower your risk.
Read about the prevention of DVT and the prevention of arterial thrombosis.
Who is at risk of blood clots?
Thrombosis is a widespread condition and a leading cause of death in the UK. Every year, over 25,000 people in England die from blood clots contracted in hospital - this is more than 25 times the number who die from MRSA.
Anyone can be affected by blood clots, although it is more common in adults over 40 years old. As well as age, a number of other factors make developing blood clots more likely. They include:
- your family history
- being inactive for long periods of time
- having damaged blood vessels as a result of infection, surgery or inflammation
- having an increased tendency for the blood to clot due to certain medical conditions or taking the contraceptive pill
Read more about the causes of DVT and the causes of arterial thrombosis.
Going into hospital is the biggest risk factor for blood clots in a vein. Although being in an aeroplane is often considered the major cause of deep vein thrombosis (DVT), two thirds of blood clots happen in hospital.
Pregnant woman also have an increased risk of developing a blood clot in a vein, depending on their age, weight and number of previous pregnancies. This risk continues for at least six weeks after giving birth.
