How can further pulmonary embolisms be prevented?

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Medication to prevent blood-clotting (anticoagulants) can prevent the recurrence of pulmonary embolism. But it’s important to carefully weigh the pros and cons because anticoagulants can cause bleeding. When considering this treatment option, doctors take into account the person’s individual risk of having another pulmonary embolism.

Anticoagulant treatment for pulmonary embolism lasts at least three months. The doctors then decide whether it makes sense to continue the treatment in order to prevent pulmonary embolism in the future.

Most people only have a pulmonary embolism once. But the risk of pulmonary embolism is higher if you’ve already had it. Because of this, a lot of people who’ve had it worry about their health.

How high is the risk of having another pulmonary embolism?

Pulmonary embolism can occur after surgery or a long period of immobility, like when someone has to stay in bed because they are ill. It can also be triggered by things like cancer, blood-clotting disorders or treatment with certain .

Good to know

The risk of having another pulmonary embolism depends on what caused the first one.

Some risk factors greatly increase the risk of having another pulmonary embolism. Others only have a small effect. Another important aspect is whether the risk factor is permanent, like a blood-clotting disorder, or temporary, like having to stay in bed after surgery.

Sometimes doctors can't work out what caused the pulmonary embolism the first time. When that happens, the likelihood of having another pulmonary embolism is higher. So, as strange as it sounds, uncertainty about the cause is a significant risk factor for further pulmonary embolisms.

Table: Different risk factors and their effect on the risk of further pulmonary embolisms
Cause of first pulmonary embolism
Examples of risk factors Risk of having another pulmonary embolism
The pulmonary embolism was caused by a major but temporary risk factor.
  • Major surgery under anesthetic
  • Major injury or fracture
  • Bed rest in hospital for at least three days
Around 2 out of 100 people per year develop another pulmonary embolism.

→ Low risk
The pulmonary embolism was caused by a minor/moderate but temporary risk factor.
  • Minor surgery with short use of anesthetic
  • Short stay in hospital
  • Bed rest at home for at least three days
  • Leg injury that limits mobility for at least three days (excluding bone fractures)
  • Long-haul flight
  • Pregnancy
  • Use of certain for contraception or menopause symptoms
Around 6 out of 100 people per year develop another pulmonary embolism.

→ Moderate risk
The pulmonary embolism was caused by a permanent risk factor (apart from cancer).
  • Inflammatory bowel disease
  • Auto-immune disease
Around 6 out of 100 people per year develop another pulmonary embolism.

→ Moderate risk
No cause found.   Around 6 out of 100 people per year develop another pulmonary embolism.

→ Experts rate the risk of having another pulmonary embolism as moderate.
The pulmonary embolism was caused by certain risk factors.
  • Cancer
  • Antiphospholipid syndrome (APS)
  • Already having several pulmonary embolisms in the past.
More than 8 out of 100 people per year develop another pulmonary embolism.

→ High risk

Are anticoagulants an effective form of prevention?

Anticoagulants are very effective at preventing further pulmonary embolisms. The preventive effect stops as soon as you stop taking them. But so does the risk of side effects, especially heavy bleeding. Whether anticoagulants have more advantages or disadvantages depends on the person’s individual situation.

How common is heavy bleeding?

Anticoagulants generally increase the risk of bleeding. Heavy bleeding like brain hemorrhages or internal bleeding can even be fatal. Heavy bleeding occurs in around 1 out of 100 people who take anticoagulants. The risk increases with age. Other risk factors for heavy bleeding include:

  • Blood-clotting disorder with a low platelet count (thrombocytopenia)
  • Use of antiplatelets like acetylsalicylic acid (the drug in medicines like Aspirin) or non-steroidal (NSAIDs)
  • Previous bleeding
  • Anemia
  • Cancer
  • Previous stroke
  • Chronic kidney or liver disease
  • Regular high alcohol consumption

The risk of bleeding can change over time – for instance, if new illnesses or poor kidney function develop due to aging. So a doctor will regularly assess the risk of bleeding. The dosage can then be adjusted as needed, or the preventive treatment can be stopped if no longer necessary. There are also various things you can do yourself to reduce the risk of bleeding and to detect bleeding early on.

When is preventive treatment considered?

Preventive treatment using anticoagulants isn't suitable for everyone who has an increased risk of developing another pulmonary embolism. Whether or not it’s the right choice for you depends on your

  • risk of having another pulmonary embolism: The higher the estimated risk, the more the anticoagulants can help.
  • risk of heavy bleeding as a side effect: The disadvantages of anticoagulants are particularly significant for people who are prone to bleeding anyway due to certain illnesses or medications.

When doctors rate the risk of further pulmonary embolisms as high, preventive treatment often has more pros than cons. Most people with a severe and permanent risk factor, like antiphospholipid syndrome, take anticoagulants permanently. Preventive treatment is also often recommended for people who have had a pulmonary embolism several times.

Preventive treatment is usually not needed if the risk of further pulmonary embolisms is considered to be low. This is especially true if the first embolism was caused by major surgery or a major injury that has since healed.

If the risk of further pulmonary embolisms is moderate, it’s often more difficult to decide whether preventive treatment is the right way to go. The line between the advantages and disadvantages is more blurred.

Good to know

The pros and cons of preventive treatment need to be considered individually for each person. Your overall health and personal preferences will play a role too.

The doctor will help you make the right decision for you. This online decision aid may help if there are a lot of things to take into account or if you first want to figure out what your personal preferences are.

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IQWiG health information is written with the aim of helping people understand the advantages and disadvantages of the main treatment options and health care services.

Because IQWiG is a German institute, some of the information provided here is specific to the German health care system. The suitability of any of the described options in an individual case can be determined by talking to a doctor. can provide support for talks with doctors and other medical professionals, but cannot replace them. We do not offer individual consultations.

Our information is based on the results of good-quality studies. It is written by a team of health care professionals, scientists and editors, and reviewed by external experts. You can find a detailed description of how our health information is produced and updated in our methods.

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Created on December 15, 2022

Next planned update: 2025


Institute for Quality and Efficiency in Health Care (IQWiG, Germany)

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