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Deep vein thrombosis

DVT (deep vein thrombosis) is a blood clot in a vein, usually the leg. They can occur in the veins of the calf, thigh or pelvis. DVT can be dangerous.

If you have symptoms of DVT, you should look for an urgent appointment with your GP.

Symptoms of DVT

Symptoms of DVT are usually:

  • throbbing or pain in your calf or thigh which is worse when walking
  • swelling, usually in 1 leg, in your ankle, calf or both
  • skin on the calf area that is warm when you touch it

DVT can be a very serious condition. Blood clots in your veins can break loose, travel through your bloodstream and get stuck in your lungs. This is called a pulmonary embolism.

Who is more likely to get DVT

The vast majority of DVTs happen in patients who are in or recently have been in hospital or a nursing home.

A DVT is more likely to happen if you:

  • are over 60
  • are overweight
  • smoke
  • have had DVT before
  • take the combined oral contraceptive pill
  • have cancer or heart failure
  • are pregnant or if you've had a baby in the previous 6 weeks
  • are staying in or recently left hospital – especially if you cannot move around much (like after an operation)
  • are confined to bed

How DVT is diagnosed

If your GP thinks you may have DVT, they will refer you to your nearest emergency department (ED).

Doctors will assess your condition and you'll have blood tests to look for fragments of a blood clot.

They may arrange for an ultrasound scan of your veins to tell if you have DVT.

You may be given an injection of heparin while you are waiting for your ultrasound scan. This is an anti-coagulant medicine. It stops blood clots from increasing in size and prevents any complications.

Treatment of DVT

If you are diagnosed with DVT, you will continue with heparin injections.

Heparin is given under the skin once a day for 4 to 5 days. You will usually be switched to a tablet form of medication after this.

Warfarin used to be the standard medication for DVTs. But newer anticoagulant medications called direct oral anti-coagulation (DOAC) are now being used. These are also known as 'novel' or 'newer' oral anti-coagulation (NOAC). You may be on this medication for at least 3 months or 6 or more months depending on the cause and extent of the DVT.

In rare cases where a leg is in danger due to a blood clot obstructing the veins, the clot can be dissolved using clot-busting drugs.

DVT in pregnancy is treated with anticoagulant injections for the rest of the pregnancy and until the baby is 6 weeks old.

Recovery from DVT

After having a DVT you will be encouraged to have regular exercise. Walking is best.

Your doctor will advise you to wear a compression stocking, usually below the knee. You should be measured and fitted for this by a healthcare professional.

Speak to your GP if you are planning a long haul flight or a long journey.

Tips to prevent DVT


  • stay a healthy weight

  • stay active – taking regular walks can help


Going on a long journey

If you're travelling for 3 hours or more by plane, train or car, there are things you can do during the journey to reduce your risk of DVT.

Take these steps to reduce your risk of DVT:

  • wear loose, comfortable clothes
  • do calf exercises at least every half hour – raise your heels, keeping your toes on the floor, then bring them down 10 times. Then raise and lower your toes 10 times
  • walk around whenever you can
  • wear a fitted compression stocking often called 'flight socks'

Going to hospital

Before you go into hospital for an elective (planned) procedure your healthcare team will have checked you for any risk factors of DVT. They will give you advice on what you need to do such as not taking the contraceptive pill.

In hospital, you may be fitted with compression stockings and given an injection of heparin under the skin to reduce the risk of developing a blood clot.

You may continue treatment after you leave hospital because a blood clot can happen weeks later.

You can also help protect yourself against DVT while you're in hospital by:

  • staying active and walking around if you can
  • moving your toes (up and down) and ankles (in circles) if you have to stay in bed – your healthcare team may give you some exercises to do

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

Page last reviewed: 22 March 2021
Next review due: 22 March 2024

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