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Pulmonary embolism

A pulmonary embolism is a blockage of a blood vessel in your lungs caused by a blood clot. It can be fatal if the clot blocks the main blood supply to your lungs.

A pulmonary embolism happens when a blood clot or a piece of a blood clot gets stuck in one of the blood vessels taking oxygen to your lungs. The clot forms somewhere else in your body and is carried to your lungs in your blood. It usually forms in one of the deep veins in your legs or your pelvis. This is called deep vein thrombosis (DVT).

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An image showing where a pulmonary embolism occurs


  • Symptoms Symptoms of pulmonary embolism

    The symptoms of a pulmonary embolism might come on suddenly, or you might not have any at all. Symptoms may include:

    • chest pain
    • breathlessness and coughing
    • fainting coughing up blood 

    The symptoms you have and how severe they are will depend on how big the pulmonary embolism is. A small embolism may not cause any symptoms. However, a large embolism can cause you to collapse suddenly and can be fatal. These symptoms could be caused by other conditions than a pulmonary embolism, but if you have any of them, see your GP. If your symptoms are severe, call for emergency help.

  • Diagnosis Diagnosis of pulmonary embolism

    If you visit your GP with minor symptoms of pulmonary embolism, he or she will ask about your symptoms, your medical history and examine you. If you have more severe symptoms, for example, trouble breathing or you collapse, you will need to go to hospital urgently. 

    If your GP thinks you may have had a pulmonary embolism, he or she will refer you to hospital. You may have an electrocardiogram (ECG) to rule out other conditions. An ECG is a simple test which records the electrical activity in your heart to see how well it's working. 

    The tests commonly used to diagnose a pulmonary embolism include the following. 

    • Blood tests, including a test for a substance called D-dimer. If the test result is negative, this may rule out DVT and a pulmonary embolism.  
    • Computed tomography pulmonary angiography (CTPA) – this test uses X-rays to make a three-dimensional image of your lungs. A dye is injected into your veins so that they show up on the X-ray image.  
    • Isotope lung scanning (also called ventilation-perfusion or V/Q scanning). This test can see how much blood is getting into your lungs. You may be offered this scan instead of a CTPA. This is most likely if you’re pregnant, if you’re allergic to the CTPA dye, or if your kidneys don’t work well.  
    • Chest X-ray, although this doesn’t always show a problem. Ultrasound scans of your legs, to look for deep vein thrombosis (DVT). 

    You may be offered additional follow-up tests once you’ve been diagnosed to find out why you’ve developed a blood clot. These may include a blood test for thrombophilia (a condition in which you’re more likely to get blood clots) and CT scan.

  • Treatment Treatment of pulmonary embolism

    A haematologist (a doctor who specialises in blood conditions and disorders) or your GP will treat your pulmonary embolism and monitor you. 

    Your doctor may give you injections of a medicine called heparin before your diagnosis has been confirmed. Heparin is an anticoagulant. This is a type of medicine that prevents blood clots forming, or stops blood clots getting larger. It doesn’t break up an existing clot – your body can usually dissolve most clots given time. The type of heparin you’re likely to have is called low-molecular-weight heparin and you’ll need to have this once a day for five days.

    If your doctor thinks you have a life-threatening pulmonary embolism, you may be given an injection of a thrombolytic medicine (eg alteplase). This helps dissolve new blood clots.

    If a pulmonary embolism is confirmed, your doctor will prescribe ongoing treatment with an anticoagulant that you take by mouth, such as warfarin. You will usually need to take this medicine for three to six months, or sometimes longer. If you develop an embolism twice for no obvious reason, or you’re at high risk of another, you may need lifelong treatment. 

    A medicine called rivaroxaban or apixaban may also be used to either treat or prevent recurrent pulmonary embolism. 

    If you’re at high risk of getting another pulmonary embolism or you can't take full anticoagulant medicines, your doctor may suggest you have an inferior vena cava (IVC) filter put in. This is a filter which sits inside the main vein carrying blood to your heart (the inferior vena cava). It traps blood clots from your legs and pelvis before they can reach your lungs. A filter may reduce your risk of getting another pulmonary embolism, although experts aren’t yet sure how well they work. 

    During your treatment, you will have regular blood tests to check how well your medicine is working. You usually won’t need to have any scans – the blood tests enable your doctor to check that the clot has gone and no more are developing.

  • Throat, airway and lung treatment on demand

    You can access a range of our health and wellbeing services on a pay-as-you-go basis, including throat, airway and lung treatments.

  • Causes Causes of pulmonary embolism

    Most pulmonary embolisms result from deep vein thrombosis (DVT) in your leg or your pelvis that becomes dislodged and moves to your lungs. You're more likely to get DVT and therefore a pulmonary embolism if you: 

    • have recently had major surgery, particularly on your abdomen (tummy), or a hip or knee replacement 
    • are pregnant or have recently had a baby 
    • have cancer 
    • are confined to bed for more than five days 
    • have had DVT or a pulmonary embolism before 
    • have a condition called thrombophilia, which means you're more likely to get blood clots (this can be inherited or got through a condition called antiphospholipid syndrome) 
    • have recently broken (fractured) your leg
    • take the combined contraceptive pill or hormone replacement therapy (HRT) 
    • are travelling for a long distance and aren’t able to move around much, for example long haul air travel 
    • are obese 
    • smoke
  • Prevention Prevention of pulmonary embolism

    If you're in hospital for an operation or because of illness, the staff will assess your risk of developing deep vein thrombosis (DVT). Being immobile can increase your risk of blood clots so your doctor may suggest you keep as active as possible. For instance, though you may not feel like it, it’s important to get up as soon as it’s safe to do so after your operation. Dehydration can also increase your chance of getting a DVT so drinking enough fluids is important too. If you're unable to drink, you may be given fluids through a drip so that you don’t become dehydrated. 

    If you're at high risk of DVT, you will be given anticoagulant medicines (medicines that prevent your blood clotting). Your doctor or nurse may recommend that you wear compression stockings to help your circulation. Compression stockings come in different sizes and your nurse will check yours are the right fit for you. You might be asked to wear them after you have had surgery until you get back to your usual levels of activity. 

    Alternatively, you may have an intermittent pneumatic compression device fitted. This device inflates regularly, putting pressure on your legs to keep the blood flowing. 

    If you're having major surgery, you’re likely to be given anticoagulant medicines (either as a tablet or as an injection) after your operation to reduce your risk of getting DVT or a pulmonary embolism. You will need to keep taking these medicines until you return to being mobile after your operation. This may be for about a week, or may be up to five weeks depending on what type of surgery you’ve had.

  • Considerations Special considerations

    If you're pregnant

    You’re at a higher risk of a blood clot when you're pregnant. This risk increases if you have pre-eclampsia (high blood pressure in pregnancy), a long labour or a caesarean delivery

    If you or members of your close family have had deep vein thrombosis (DVT) or a pulmonary embolism in the past, you may be offered screening for a blood clotting disorder (thrombophilia). You’ll also be offered this if you’ve had three consecutive miscarriages during your first trimester. 

    If your doctor thinks you're at high risk of getting a blood clot, they may offer you heparin injections during your pregnancy. These will prevent blood clotting. You may need to continue these injections for six weeks after you have given birth. Your doctor may also recommend you wear elastic compression stockings.

  • FAQs FAQs

    Could anticoagulants harm my unborn baby?


    Some anticoagulants (medicines that prevent your blood clotting) could harm your developing baby, so you shouldn't take them if you're pregnant. Warfarin is one such medicine. If you're pregnant and need to take an anticoagulant, your doctor will usually advise you to have injections of a medicine called heparin. Heparin is safer because it doesn’t cross the placenta. 


    You may need to take an anticoagulant medicine while you're pregnant if your doctor thinks you're at risk of developing deep vein thrombosis (DVT) and a pulmonary embolism. 

    Anticoagulants that you take by mouth, such as warfarin, are not usually suitable during pregnancy. This is because they can cross the placenta (which delivers oxygen and nutrients to your baby) and so may harm your developing baby. If you’re taking warfarin and think that you might be pregnant, tell your doctor immediately. 

    Pregnant women who need anticoagulant treatment can take heparin because it doesn't cross the placenta, so it won't reach your baby. Heparin is taken by injection. If you’re taking an oral anticoagulant, such as warfarin, you’ll be advised to switch to heparin as soon as your pregnancy is confirmed. In special cases, such as if you have a mechanical heart valve fitted, your doctor may suggest you continue to take warfarin during pregnancy. Your doctor will discuss the risks and benefits with you. 

    Sometimes you may need to continue using low-molecular-weight heparin after the birth of your baby. This is usually for seven days but may be for up to six weeks, depending on your risk of getting a blood clot. You can take both warfarin and low-molecular-weight heparin while breastfeeding.

    I'm taking the combined contraceptive pill – what’s the risk of getting a pulmonary embolism?


    If you take the combined contraceptive pill, you have a slightly increased risk of blood clots including pulmonary embolism. However, the risk is small and doesn’t outweigh the benefits of the pill for most women. And, the risk is less than the risk of pulmonary embolism associated with pregnancy. 


    Combined oral contraceptive pills contain a artificial (man made) form of the hormone oestrogen. Taking oestrogen increases your risk of blood clotting including deep vein thrombosis (DVT) and pulmonary embolism. Women who take the combined contraceptive pill are about three to five times more likely to have a blood clot than women who don’t take the pill. 

    Although you may be at an increased risk of getting DVT or a pulmonary embolism if you take the contraceptive pill, it's still rare to get one of these conditions. Your risk of having a blood clot when taking the combined contraceptive pill is lower than your risk of clots if you become pregnant. However, your overall risk may be much higher if you take the combined contraceptive pill and have other risk factors for DVT and a pulmonary embolism. 

    Other risk factors include being very overweight, being older than 35 and having a family member who has had a blood clot. Because of this, your doctor will ask you about your medical and family history before you start taking the contraceptive pill. 

    Women taking the combined contraceptive pill also have a slightly higher risk of getting DVT during surgery. If you're having surgery, your doctor will talk to you about the risks and benefits of stopping taking the pill beforehand. The small reduction you may get in your risk of DVT has to be balanced against the risk of unplanned pregnancy if you stop taking the pill.

    Will I be at risk of pulmonary embolism if I take a long flight?


    If you fly long distances, or even travel long distances by bus, train or car, you may increase your risk of getting a blood clot and a pulmonary embolism. However, most people who develop blood clots after a long journey also have other risk factors for these conditions.


    Sitting down on a long journey means that your legs are inactive for a long time. When your legs are inactive, the blood flow slows down. This can increase your risk of getting a blood clot in your leg (deep vein thrombosis, DVT) which can then travel to your lungs (pulmonary embolism). 

    Long distance air travel may increase your risk of pulmonary embolism by about three times, but the risk is still a small one. This slight increased risk is similar if you travel long distances by bus, train or car – all situations where you are sitting still for long periods. You’re most at risk if you travel for more than eight to 10 hours, or do multiple journeys of over four hours. Your increased chance of getting a blood clot and pulmonary embolism may last for up to eight weeks after your journey. 

    Most people who get travel-associated DVT and pulmonary embolism have other risk factors. These include having had a previous blood clot, being obese, having recently had surgery or having a family member who has had a blood clot. You may also be at increased risk if you are pregnant. There are some simple steps you can take to reduce your risk of DVT or pulmonary embolism from flying.  

    • Walk around the cabin whenever you can. 
    • Do simple leg exercises in your seat; for example, flex your ankles.
    • Drink enough water so you don’t become dehydrated. 
    • Don't drink too much alcohol or coffee (these can cause dehydration). 
    • Ask for an aisle seat if possible. 

    If you think you might be at risk of getting a DVT or pulmonary embolism while travelling, speak to your GP. If you will be travelling for more than six hours, your GP may advise you to wear compression stockings. Your GP may also advise you to have an injection of a medicine called heparin, which prevents blood clots, immediately before you travel. They will only advise this if you’re at higher risk.

  • Resources Resources

    Further information


    • Pulmonary embolism. BMJ Best Practice., published 20 December 2013 
    • Kumar P, Clark M. Clinical medicine. 8th ed. Edinburgh: Saunders; 2012 
    • 2014 ESC Guidelines on the diagnosis and management of acute pulmonary embolism. The task force for the diagnosis and management of acute pulmonary embolism of the European Society of Cardiology (ESC). 
    • Pulmonary embolism. PatientPlus., reviewed 2 October 2012 
    • Pulmonary embolism. The Merck Manuals., published November 2013 
    • Pulmonary embolism. NICE Clinical Knowledge Summaries., published June 2013 
    • Longmore M, Wilkinson I, Baldwin A, et al. Oxford Handbook of Clinical Medicine. 9th ed. Oxford: Oxford University Press; 2014 
    • Map of Medicine. Pulmonary embolism. International View. London: Map of Medicine; 2013 (Issue 4) 
    • Venous thromboembolism: reducing the risk. National Institute for Health and Clinical Excellence (NICE), January 2010. 
    • ECG. British Heart Foundation., accessed 23 September 2014 
    • Reducing the risk of thrombosis and embolism during pregnancy and the puerperium. Royal College of Obstetricians and Gynaecologists, 2009. 
    • Preventing deep vein thrombosis in hospital by using intermittent pneumatic compression devices (IPC). Lifeblood, the Thrombosis Charity., accessed 23 September 2014 
    • Young T, Tang H, Hughes R. Vena caval filters for the prevention of pulmonary embolism. Cochrane Database of Systematic Reviews 2010, Issue 2. doi:10.1002/14651858.CD006212.pub4 
    • Combined hormonal contraceptives. European Medicines Agency., accessed 24 September 2014 
    • Combined hormonal contraceptives. MHRA., accessed 24 September 2014 
    • Bartholomew J, Schaffer J, McCormick G. Air travel and venous thromboembolism: minimizing the risk. Cleveland Clinic Journal of Medicine 2011; 78(2):111–20. doi:10.3949/ccjm.78a.10138 
    • Sugerman H, Eklöf B, Toff W, et al. Air travel-related deep vein thrombosis and pulmonary embolism. JAMA 2012; 308(23):2531. doi:10.1001/jama.2012.4098
    • Travelers’ health. Deep vein thrombosis and pulmonary embolism. Centers for Disease Control and Prevention., accessed 24 September 2014
    • How is pulmonary embolism treated? National Heart, Lung and Blood Institute., accessed 25 September 2014 
    • Pulmonary angiography. Medscape., published 6 September 2013 
    • Pulmonary embolism. Medscape., published 2 September 2014 
    • Personal communication, Dr Shankara Paneesha, Consultant Haematologist, Heart Of England NHS Foundation Trust, 17 February 2015 
    • Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing. National Institute of Health and Care Excellence (NICE), June 2012. 
    • Baglin TP, Brush J, Streiff M. British Committee for Standards in Haematology Writing Group. Guidelines on use of vena cava filters. Brit J Haematol 2006; 134:590–95. doi:10.1111/j.1365-2141.2006.06226.x 
    • Inferior vena cava filter placement and removal., published 12 February 2014
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