Blood clots

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

Symptoms of blood clots

Immediate action required: Seek medical help immediately if you have one or more of these symptoms:

  • swelling or pain in one leg or calf
  • warmth or redness in a leg
  • shortness of breath or rapid breathing
  • chest pain, which may be worse when you breathe in
  • a cough or coughing up blood

There are treatments to deal with and help prevent blood clots, which are very effective.

What a blood clot in a leg can look like

swollen and red left leg
Swelling and redness caused by a clot in the left leg
swollen right leg
Red and swollen right leg caused by a clot

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

Immediate action required: Call 112 or 999 or go to your nearest emergency department if:

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

This could be a blood clot in the lungs which needs to be treated immediately.

Check if you're at risk of blood clots

You're more likely to get them if you:

  • are admitted to hospital and for 90 days after you go home
  • are pregnant or have had a baby less than 6 weeks ago
  • have active cancer or receiving cancer treatment
  • have one or both legs immobilised, for example in a leg cast
  • are overweight

There are also other things that increase your risk of clots, such as:

  • smoking
  • using combined hormonal contraception such as the combined pill, contraceptive patch or vaginal ring
  • having had a blood clot before

Preventing 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.


  • keep moving – even if you’re sick in bed try to move your legs and feet every 90 minutes

  • drink plenty of water to avoid dehydration – your pee should be light yellow or clear


  • 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

Read more about Blood clots on the Thrombosis Ireland website

Content supplied by the NHS and adapted for Ireland by the HSE

Page last reviewed: 27 May 2020
Next review due: 27 May 2023

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.