Deep vein thrombosis (DVT)

Expert reviewer, Dr Shankara Paneesha, Consultant Haematologist
Next review due October 2022

Deep vein thrombosis (DVT) is where a blood clot forms in one of your deep veins. This is usually in one of the large veins in your leg. You can also get DVT in your pelvis, your arm or your abdomen (tummy).

DVT may cause pain and swelling. If the blood clot moves and travels to your lungs, it can lead to a pulmonary embolism, which can be life-threatening. So if you have a DVT, you’ll need treatment to stop this happening.

DVT symptoms

Many people with DVT won’t have any symptoms at all.

If you have a large blood clot that mostly or totally blocks your vein, you may have some symptoms. These include:

  • a swollen leg, or legs
  • pain and tenderness, usually in your calf, or your inner thigh
  • warm skin that looks red

These can often be symptoms of other conditions too. In fact, only about one in two people with a swollen and painful leg will have DVT. If you have any of these symptoms, contact your GP as soon as possible.

Diagnosis of deep vein thrombosis

Your GP will ask about your symptoms and medical history and examine you. They’ll assess how likely you are to have a DVT, based on all your symptoms and risk factors. If your GP thinks a DVT is likely, they’ll recommend you have some urgent tests to confirm the diagnosis. These may include the following.

  • A blood test called a D-dimer. This measures a substance which develops in your body when a blood clot breaks down. The test is usually used to rule out DVT as the cause of your symptoms. However, D-dimer tests may be positive or raised even if you don’t have DVT. This may be if you have other health conditions such as liver disease or an infection, if you’re pregnant or you’ve recently had an operation. So if the test is positive, you’ll need further tests to see if you actually do have DVT.
  • A leg vein ultrasound. This uses sound waves to look at the blood flow through the blood vessels in your leg.

Treatment of deep vein thrombosis

If you have DVT, your doctor will recommend treatment. This is to:

  • stop it getting worse
  • reduce your risk of getting a pulmonary embolus
  • make it less likely that you’ll get another DVT


The main treatment for DVT is a type of medicine called an anticoagulant. Anticoagulants prevent blood clots forming or stop blood clots getting bigger.

If your doctor suspects you have a DVT, they may recommend you start treatment with an anticoagulant even before your diagnosis is confirmed. Which type of anticoagulant your doctor recommends will depend on your general health and what caused your DVT, as well as local guidelines and your doctor’s own experience.

The two main types of anticoagulant treatment used for DVT are:

  • heparin (injections) plus warfarin (tablets)
  • direct oral anticoagulants (DOACs) such as apixaban, edoxaban and rivaroxaban. These are fairly new medicines, taken as tablets.

Heparin and warfarin

Heparin is given as an injection under your skin, while warfarin is taken as tablets. You’ll need to have both treatments to begin with, because it takes a few days for the warfarin to start to work. You’ll be able to stop the heparin after around five days. But you’ll probably need to continue taking the warfarin tablets for three to six months, sometimes longer. You’ll need to have regular blood tests to make sure your blood is clotting properly.

Direct oral anticoagulants (DOACs)

These newer medicines have the advantage that you don’t need to be monitored as closely as with warfarin. And they act quickly so you may not need heparin injections to get your treatment started. If you have certain health conditions, an increased risk of bleeding or are pregnant, you may not be able to have DOACs.

Taking anticoagulants

You can usually receive anticoagulant treatment for DVT through your GP or as an out-patient at your local hospital. But you may need to be admitted to hospital for treatment if you have any complications, or if you’re at increased risk of bleeding.

If your symptoms get worse when you begin taking anticoagulants or if you develop another DVT, your doctor may try switching you to an alternative treatment.

Depending on your medical history and why you developed a DVT, your doctor may recommend you continue taking anticoagulant medicines for the long term. This is to prevent any more blood clots developing.

The main side effect of taking anticoagulant medicines is bleeding. If you’re taking anticoagulants, you should be given an anticoagulant information booklet and an alert card, which you should always carry with you. The card lets other health professionals know that you’re taking these medicines in case of an emergency or before you have any other treatment.

If you’re taking warfarin, you’ll need to have regular blood tests to check how well your blood is clotting. This blood test is called an INR test. Having the INR test can help your doctor to make sure you’re getting the right amount of medicine and adjust it if necessary. You won’t need INR tests if you’re taking direct oral anticoagulants (DOACs).

You can reduce your chance of bleeding by carefully following the advice given in the patient information leaflet that comes with your medicine.

For more information about taking anticoagulants, see our FAQ ‘How can I reduce my risk of bleeding with DVT anticoagulants?’ below.

Inferior vena cava filters

Most people with DVT can have treatment with anticoagulants. But if you can’t, or it doesn’t work, your doctor may suggest you try treatment with a device called an inferior vena cava (IVC) filter. An IVC filter is a small metal device placed inside a vein to trap any clots before they can travel to your heart and lungs. You may also have one if you have recurrent DVT (it keeps coming back).

Ongoing treatment

After having a DVT your doctor may encourage you to:

  • start walking again as soon as possible as this can ease your symptoms
  • keep your leg up while you are resting, to keep it comfortable

If you need pain relief, you could take over-the-counter medicines paracetamol or co-codamol. You shouldn’t take aspirin or non-steroidal anti-inflammatory medicines (NSAIDs, like ibuprofen) when taking anticoagulants. You can ask your pharmacist for advice. If your pain doesn’t go away, your doctor may recommend you have another ultrasound scan to make sure there is no worsening of the blood clot.

Your doctor may suggest you wear a compression stocking on the affected leg for up to two years afterwards. These are tight stockings that help to pump your blood through your legs. They can help to reduce any ongoing symptoms you have, and they’re thought to reduce your risk of developing post-thrombotic syndrome (see Complications below for more information). You wear compression stockings during the daytime and take them off at night. You can get them from your pharmacy. It’s important to get stockings that fit properly – ask your pharmacist for advice.

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Causes of deep vein thrombosis

There are many factors linked to developing DVT. These may act together, and include:

There are certain things that are known to be associated with developing DVT. These include:

  • being inactive for long periods of time; for example, if you’re recovering after a big operation or are sitting still during a long journey
  • having blood that clots more easily; for instance, if you’re pregnant, have certain conditions that affect your blood clotting, or you’re taking the contraceptive pill
  • having an inherited (genetic) condition that means your blood clots more easily
  • having cancer
  • if your blood vessels have been damaged from an injury or operation

You’re also at greater risk of developing a DVT if:

  • you’ve had DVT before
  • you're over 60
  • you smoke
  • you’ve very overweight (obese)
  • you’re dehydrated (not getting enough fluid)
  • you have a severe infection

Travel risks

If you travel long distances and spend more than about four hours sitting down, then you could be more likely to develop deep vein thrombosis. This is especially true of travel by plane, where the risk of DVT is doubled or trebled after about four hours. The risk is not large – it’s thought that around one person in 6,000 gets DVT after a long haul flight. The longer the journey, the greater your chances of getting a blood clot.

See our section on prevention below, for tips on how to reduce the chance of getting DVT when travelling.

If you get DVT after a long journey, you may not notice any symptoms straightaway. It can take hours, days or even weeks before you notice anything. If you talk to a doctor, always mention your recent travel so they can take this into account.

Complications of deep vein thrombosis

Most of the time, deep vein thrombosis (DVT) doesn’t cause any further problems. However, possible complications of DVT can include the following.

Pulmonary embolism

A pulmonary embolism happens when a blood vessel in your lungs becomes blocked. A piece of the blood clot in your leg can break off and travel through your body in your bloodstream until it gets to your lungs, where it gets stuck. If blood isn’t reaching your lungs properly, it can be very serious. Getting treatment quickly can be life-saving.

Post-thrombotic syndrome

This is when you have ongoing symptoms after a DVT, such as a painful and swollen leg and sore, dry skin. It can happen if the damage caused by DVT increases the pressure in your vein. If the condition becomes severe, you could develop an ulcer on your leg and this can be difficult to heal. Wearing compression stockings may help to prevent post-thrombotic syndrome.

Prevention of deep vein thrombosis

If you're in hospital for a big operation or because of illness, you may be more likely to develop deep vein thrombosis. When you’re in hospital, your nurse or doctor will assess your risk of developing a blood clot. You may be asked to do the following to reduce your risk.

  • Drink plenty of fluids. If you can’t drink, you’ll be given fluids through a drip.
  • Get up and start moving about as soon as you can after an operation or illness.
  • Wear compression stockings to help your circulation.
  • Have an injection of an anti-clotting medicine as well as or instead of wearing compression stockings.
  • Use an intermittent pneumatic compression device. This is an inflatable cuff wrapped around your leg or foot and an electrical pump that inflates it, squeezing your deep veins.

You can also help prevent blood clots from developing during a long journey by doing the following.

  • Get up and walk around whenever you can.
  • Do leg exercises in your seat, for example, bend and straighten your knees, feet and toes every half hour.
  • Drink enough fluid so you don’t become dehydrated, and don’t drink excessive amounts of alcohol.
  • Wear comfortable, loose clothing.

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Related information

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    • Personal communication, Dr Shankara Paneesha, Consultant Haematologist, October 2019
  • Reviewed by Dr Kristina Routh, Freelance Health Editor, Bupa Health Content Team, October 2019
    Expert reviewer, Dr Shankara Paneesha, Consultant Haematologist
    Next review due October 2022