NHS website

Blood clots

Every year, thousands of people in the UK develop a blood clot in a vein. It's known as venous thromboembolism (VTE) and is a serious, potentially fatal, medical condition.

11 December 2018


Blood clots can be very serious and need to be treated quickly. Staying healthy and active can help prevent them.

See a GP urgently if you think you have a blood clot

Symptoms of a blood clot include:

  • throbbing or cramping pain, swelling, redness and warmth in a leg or arm
  • sudden breathlessness, sharp chest pain (may be worse when you breathe in) and a cough or coughing up blood

Blood clots can be life threatening if not treated quickly.

Go to A&E or call 111 for advice if you can't get a GP appointment the same day.

Find an A&E department ↗

What a blood clot in a leg can look like

A blood clot in a leg is called deep vein thrombosis (DVT) ↗.

Call 999 or go to A&E if:

  • you're struggling to breathe
  • someone has passed out

This could be a blood clot in the lungs (pulmonary embolism) ↗, which needs to be treated immediately.

Check if you're at risk of blood clots

Blood clots are rare in young, healthy people.

You're more likely to get them if you:

  • are staying in or recently left hospital – especially if you can't move around much (like after an operation)
  • are overweight
  • smoke
  • are using combined hormonal contraception such as the combined pill ↗, contraceptive patch ↗ or vaginal ring ↗
  • have had a blood clot before

There are also other things that increase your risk of clots.

How to prevent blood clots

If you're at a high risk of blood clots – for example, you're in hospital – follow the advice of your care team about preventing clots.

This may involve wearing stockings that improve your blood flow or taking medicine to reduce the risk of clots (anticoagulants) ↗.

There are also things you can do to help avoid clots.


  • stay active – even just taking regular walks can help
  • drink plenty of water to avoid dehydration ↗ – you're more likely to get a clot if you're dehydrated
  • try to lose weight if you're overweight
  • wear flight stockings or flight socks to improve your blood flow on long flights – a pharmacist can advise you about this


  • do not sit for long periods without moving, if you can avoid it
  • do not drink lots of alcohol – this can make you dehydrated
  • do not smoke

Social care and support guide

If you:

  • need help with day-to-day living because of illness or disability
  • care for someone regularly because they're ill, elderly or disabled, including family members

Our guide to care and support ↗ explains your options and where you can get support.