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Pulmonary embolism - Treating pulmonary embolism

The main treatment for a pulmonary embolism is a type of medication called an anticoagulant, which stops your blood clotting easily.

The anticoagulant will prevent the clot getting larger while your body slowly absorbs it. It also reduces your risk of further clots developing.

In some cases, other treatments may be needed to remove or break up the clot. This can be done with medication called thrombolytics or, less commonly, surgery.

About half of all pulmonary embolisms occur in hospital. If you are not already in hospital, you will be admitted so you can receive treatment. If necessary, you will be given oxygen through a mouthpiece to help you breathe more comfortably.


Anticoagulants are often referred to as blood-thinning medicines, although they do not actually thin the blood. Instead, they alter chemicals in the blood to prevent clots forming easily.

The main anticoagulants used to treat pulmonary embolisms are low molecular weight heparin and warfarin.

Low molecular weight heparin is given as an injection. Regular injections of this medication are usually used as the initial treatment for a pulmonary embolism because they start working immediately.

Warfarin comes in tablet form, which you will usually take soon after the initial treatment with low molecular weight heparin. Warfarin takes longer to start working than heparin injections, but as it's more convenient to take, it's usually recommended for a longer period after you stop having these injections.

These medications are discussed in more detail below.

Low molecular weight heparin

There are two different types of heparin injection that may be used to treat a pulmonary embolism – standard (unfractioned) heparin and low molecular weight heparin (LMWH).

Most people diagnosed with a pulmonary embolism will initially require injections of LMWH for at least five days. After this initial treatment finishes, you will usually continue taking warfarin only.

Unfractioned heparin is rarely used nowadays because this type of heparin can work differently from person to person, which means you need to stay in hospital during treatment so your dose can be carefully monitored and adjusted if necessary.

LMWH works slightly differently from unfractioned heparin. It contains smaller molecules, which means that its effects are more predictable. LMWH can be given as regular injections without the need to stay in hospital to be monitored.

LMWH can cause side effects, including:

Serious side effects are less likely to occur if you are taking LMWH, which is another reason why these medications will be recommended in most cases instead of unfractioned heparin.


If you are diagnosed with a pulmonary embolism, you will usually start taking warfarin tablets when you have the initial injections of LMWH.

Treatment with warfarin will usually be recommended for at least three months, although some people need to take it for longer than this. Occasionally, warfarin may need to be taken for the rest of your life.

Like unfractioned heparin, the effects of warfarin vary from person to person, so you will need to be closely monitored and have regular blood tests to ensure you are taking the right dosage. These tests can usually be carried out on an outpatient basis, which means you won't need to stay in hospital.

You may need to have two or three blood tests a week when you first start taking warfarin until the correct dose is determined. After this, you may only need to have a blood test about once a month.

There are several factors that can alter the effectiveness of warfarin, including your diet, other medications you are taking and how well your liver is working.

While taking warfarin, you should therefore: 

  • try to keep your diet consistent
  • limit your consumption of alcohol and do not drink more than the recommended amounts (three to four units a day for men and two to three units a day for women)
  • take your medication at the same time each day
  • not take any other medicine without first checking with your GP, pharmacist or anticoagulant specialist
  • avoid taking herbal medicines

As with heparin and fondaparinux, warfarin can cause a wide range of side effects, including:

  • bleeding problems
  • headaches
  • diarrhoea
  • nausea and vomiting 
  • jaundice (yellowing of the skin and whites of the eyes)

Read more about the side effects of warfarin.  

Special considerations

There are some situations where your anticoagulant treatment may be different from normal.

For example, if you are pregnant, you will be given regular LMWH injections instead of warfarin tablets for the full length of your pregnancy. This is recommended because taking warfarin tablets while you are pregnant could harm your baby.

If you have cancer, you will usually be given LMWH injections instead of warfarin tablets for six months, or until the cancer is cured. This is recommended because evidence suggests that regular injections are more effective than warfarin tablets in these cases.

Removing the blockage

In more severe cases, treatment may be needed to remove the blockage.

This is usually done using injections of a type of medication called a thrombolytic, such as alteplase, which breaks up the blood clot.

Occasionally, a surgical procedure called an embolectomy may be used to treat a pulmonary embolism. This is where a surgeon makes a cut in the pulmonary artery and the blockage is sucked out.

However, this is a major operation so it is usually only recommended in particularly severe cases or if other treatments are unsuitable.

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