Blood clot in a vein (venous thrombosis)

Developing a blood clot in a vein is a serious, potentially fatal, medical condition. Deep vein thrombosis (DVT) is a blood clot that develops within a deep vein in the body, usually in the leg. This page has information on what causes blood clots and ways to help prevent them.

About blood clots in a vein 

A blood clot in a vein is known as venous thrombosis.

If the blood clot, or part of it breaks away, it can travel through the bloodstream, causing blockage in an artery.  This is known as venous thromboembolism (VTE) and is a serious medical condition.

If the clot travels in the bloodstream to the lungs, this causes a pulmonary embolism (PE), and this can be fatal.

Although serious, most blood clots can be avoided. The key is to be aware if you're at risk and take some simple preventative steps.

This article is about blood clots in veins. If you want information on blood clots in arteries, which is a common cause of heart attack and stroke, see the page on arterial thrombosis.

How to tell if you have a blood clot 

Before leaving hospital, you should be told about anything you need to look out for that could suggest you've developed a blood clot.

Symptoms of a blood clot can include:

If you develop symptoms of a blood clot, see your GP or go to your nearest emergency department as soon as possible.

Blood clots can be treated if they're spotted in time. Read more about treating blood clots.

Who gets blood clots? 

Anyone can get a blood clot, but you're more at risk if you can’t move around much or if you’re unwell.

Most blood clots actually develop during or just after a stay in hospital.

Your risk is also increased if you:

  • are unable to move around – for example, after an operation or sitting on a long haul flight
  • are over 60 years old
  • are overweight or obese
  • have had a blood clot before
  • are having hormone treatment – for example, hormone replacement therapy (HRT) or taking a contraceptive pill
  • are pregnant or have recently given birth
  • are dehydrated
  • have heart failure
  • have cancer or are having cancer treatment
  • suffering severe infection
  • have a condition that causes your blood to clot more easily than normal, such as antiphospholipid syndrome

Reducing your risk of blood clots in hospital 

There are things you and the medical professionals looking after you can do before, during and after a hospital stay to minimise your risk of developing a blood clot.

Before coming into hospital

You can help yourself before coming into hospital by:

  • trying to lose any excess weight
  • keeping as mobile as you can
  • talking to your doctor if you take HRT or the combined contraceptive pill – you may need to stop them a few weeks before your operation

While in hospital

While you're in hospital, you will reduce your chances of a blood clot if you:

  • drink plenty of fluids to keep hydrated
  • wear your compression stockings day and night (except when you're washing)
  • wear any other compression devices you've been given
  • take any blood-thinning medicines you've been offered
  • get up and move around as soon as you're advised to

After leaving hospital

You're still at risk of developing a blood clot in the days and weeks after leaving hospital. So you might be advised to continue preventative measures for a short period. Your care team will discuss this with you before you are discharged.

You may be given compression stockings to wear until you are fully mobile. You may need to keep using anticoagulants for several weeks. You should also take care to stay as mobile as possible and keep yourself well hydrated.

The information on this page has been adapted from original content from the NHS website.

For further information see terms and conditions.

This page was reviewed November 2018

This page is due for review December 2019

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