Pulmonary embolism

At a glance

  • Pulmonary embolism happens when a blood clot blocks a blood vessel in the lungs.
  • Common symptoms include sudden difficulty breathing, chest pain, coughing up blood, dizziness, feeling faint, and a racing heart.
  • Severe pulmonary embolism can be fatal and must be treated in a hospital as soon as possible.
  • The main treatment is medication to prevent blood clotting.


Photo of man holding his chest in pain

Pulmonary embolism is a rare but serious complication of thrombosis. It happens when a blood clot (thrombus) breaks free from the wall of a vein, travels through the bloodstream and then blocks one or more blood vessels in the lungs (pulmonary vessels). This makes it more difficult for the lungs to absorb oxygen.

Pulmonary embolism has to be treated quickly because the blood backs up to the heart if a lung vessel is blocked. This can put too much strain on the heart and lead to life-threatening heart failure. Because of this, it’s very important to call the emergency services straight away (112 in Germany and many other countries, 911 in the U.S.) if someone has typical symptoms like extreme difficulty breathing, chest pain and coughing up blood.

Pulmonary embolism is treated with medication to prevent blood clotting. In severe cases, further treatment may be needed to break up or remove the clot.

The risk of pulmonary embolism increases after things like major operations – such as knee or hip replacement surgery. Because of this, people usually take medications to prevent blood clots for a while after having this kind of surgery.


The typical signs of pulmonary embolism are:

  • Sudden, extreme difficulty breathing
  • Chest pain
  • Coughing – especially coughing up blood, or together with other pulmonary embolism symptoms
  • Dizziness, feeling drowsy or even losing consciousness
  • Rapid heartbeat
  • Extreme anxiety

These symptoms are often a sign that one or more large blood vessels in the lungs are blocked.

Some people with pulmonary embolism don’t have any symptoms, or only have mild ones.

At first I just had slight back pain and thought I had strained something. But later I could no longer lie down because then I couldn’t breathe. And I was sweating heavily.

Stephan, 45 years old


Pulmonary embolism is usually caused by venous thrombosis, where a blood clot (thrombus) forms in a vein. This leads to pulmonary embolism if the whole clot or part of it travels through the bloodstream toward the heart and blocks an artery in the lungs – or blocks a smaller blood vessel that branches off an artery in the lungs. The (part of the) thrombus that breaks off and travels through the bloodstream is called an embolus. "Pulmonary" is the medical term for things related to the lungs.

Illustration: How thrombosis leads to pulmonary embolism

Most thrombus blood clots develop in a leg or pelvic vein. The risk of pulmonary embolism is higher if the clot forms in the upper thigh or pelvis, or if it causes severe symptoms.

In very rare cases, pulmonary embolism is caused by other things that block an artery in the lungs – like an air bubble or something else that shouldn’t be there.

Risk factors

Generally speaking, risk factors for deep vein thrombosis also increase the risk of pulmonary embolism. The risk is particularly high when someone has several risk factors. The main ones are:

  • Hip or leg fractures
  • Major operations like knee or hip replacement surgery
  • Disorders that increase the risk of blood clotting, like antiphospholipid syndrome
  • Previous thrombosis
  • Cancers like stomach or lung cancer, leukemia or brain tumors
  • Heart disease like heart failure, a or
  • Hormone replacement therapy (HRT) for menopause
  • Use of hormone-based contraceptives that contain the hormone estrogen (which most contraceptive pills do)

Some other risk factors only increase the risk of pulmonary embolism slightly if they occur on their own. They include:


The risk of pulmonary embolism increases with age: It occurs in about 1 out of 1,000 people between the ages of 40 and 50, and in roughly 10 out of 1,000 people aged 80 and over.

Generally speaking, pulmonary embolism is more common in men than in women. But women under 45 and over 80 develop it more often than men of the same age. Younger women have a slightly higher risk if they are pregnant or use hormone-based contraception.


The effects of pulmonary embolism will depend on how many clots are in the lungs and how big they are. The person’s general health also plays a role – especially how well their heart and lungs work.

Illustration: Heart strain due to pulmonary embolism

The heart usually manages to pump blood despite the blocked blood vessel in the lungs. But if the heart is weak (due to illness, for example) it can't pump enough blood into the lungs. Then the blood circulation decreases and blood pressure drops. If the body doesn’t get enough oxygen, there is a risk of cardiovascular collapse.

So the blood pressure level during the pulmonary embolism is a good indicator of how things will go: Out of 100 people with pulmonary embolism, blood pressure is

  • high enough in around 95 of them. Their overall risk of severe or fatal embolism is low.
  • far too low in 5 people. Their risk of severe or fatal embolism is high.

It is also possible to have an embolism more than once – especially if you have ongoing risk factors like cancer or a blood-clotting disorder.


A lot of people still have breathing problems or a lower level of physical fitness months after they had pulmonary embolism. This is called “post-pulmonary embolism syndrome.”

In rare cases, pulmonary embolism can result in a condition known as “chronic thromboembolic pulmonary disease” (CTEPD). It is not entirely clear why this happens. Experts assume that the clot in the lungs becomes scar tissue instead of breaking down completely. If this causes a permanent blood pressure increase in the vessels of the lungs, the medical term used is “chronic thromboembolic pulmonary hypertension” (CTEPH). Severe CTEPH puts a lot of strain on the heart and can lead to heart failure.

The symptoms of CTEPH are non-specific. In other words, they can also be caused by many other medical conditions. CTEPH can trigger the same symptoms as pulmonary embolism and post-pulmonary embolism syndrome can. If your physical fitness gets worse several weeks or months after pulmonary embolism, or you even have difficulty breathing and start coughing up blood, it’s important to see a doctor quickly to find out why.


Symptoms like sudden chest pain or difficulty breathing can have other causes, including or . You should always call the emergency services (112 in Germany and many other countries, 911 in the U.S.) if you develop these symptoms. It is important to find out quickly what’s causing them. If doctors at the hospital think you might have a pulmonary embolism, they will do tests straight away so they can react quickly if it turns out to be a severe case. The tests they do will particularly depend on

  • how stable your blood circulation is: It is considered to be unstable if the systolic blood pressure is lower than 90mmHg for at least 15 minutes or if it drops down very low. The medical term for this is “hemodynamic instability.” Otherwise, your blood circulation is considered to be stable.
  • the likelihood of pulmonary embolism: This depends on things like whether you have a fast heartbeat, recently had surgery, or have deep vein thrombosis or cancer. Another factor is whether your heart is under extreme strain or is damaged.

To reach a , doctors often have to do a series of tests in a certain order.

Blood test (D-dimer test)

This test reacts to substances called D-dimers, which are released when the body breaks down blood clots. If the test result is normal, your blood pressure is stable and you generally have a low risk of pulmonary embolism, then it is quite certain that you don't have pulmonary embolism. If the test result is not normal, the next step is to use imaging.


Doctors might do an ultrasound scan (sonogram) of the veins in your legs. If this shows that you have a thrombosis, you will be diagnosed with pulmonary embolism. If not, more testing is needed. The ultrasound scan doesn’t use radiation so it’s particularly suitable in pregnancy.

An ultrasound scan of the heart (echocardiogram, sometimes just called an "echo") can show how much strain is on the right side of the heart. The other imaging techniques involve exposure to radiation and use of a contrast agent. Because of this, they’re only used if the doctors think it’s very likely that you have a pulmonary embolism. In people with hemodynamic instability (unstable blood circulation), these other imaging techniques are used straight away to ensure a rapid .

A CT () pulmonary angiogram (CTPA) is a special type of x-ray examination. A contrast agent is injected into a vein in your arm. It contains iodine, which allows doctors to see the blood clot in the lung.

A ventilation/perfusion scan (scintigraphy) is sometimes done when a CTPA isn't possible or is too much of a risk – for example, for people who are pregnant, have kidney disease or are allergic to the contrast agent. This scan shows the flow of blood and air in the lungs. It involves a combination of inhaling a weak radioactive substance and having it injected into your vein.


The treatment options for pulmonary embolism mainly depend on whether your blood circulation is stable (hemodynamic stability).

Stable blood circulation

People often spend a few days in hospital and are given medication to prevent blood-clotting. The medical term for this medication is “anticoagulants” and the treatment is called “anticoagulation.”

It makes sure existing clots don’t grow and no new ones appear. Your body can then gradually get rid of the clot that’s already there. The most common side effect of this medication is bleeding, especially in the digestive tract.

A sudden deterioration is possible (but rare) even if your blood pressure is stable. If you start showing signs of this rare complication, you’ll be placed in intensive care for observation for a few days.

Unstable blood circulation

If your circulation is unstable, you’ll normally have to be treated in intensive care. The staff will use various methods to help you breathe and to keep your blood circulating properly. These include drips, ventilators and medication. You will also be given anticoagulants immediately – usually even before you get the final .

The doctors will also consider whether it makes sense to use systemic thrombolysis or minimally invasive surgery to remove the clot. Thrombolysis involves injecting medication into a vein so that it can dissolve the clot in the lungs. The treatment is called “systemic" thrombolysis because the medication travels around the whole "body system" rather than just being used locally (in one specific area of the body). But thrombolysis can lead to larger-scale internal bleeding, especially in the head. So it isn’t suitable for everyone with severe pulmonary embolism.

If systemic thrombolysis isn’t possible, doctors can destroy or remove the clot mechanically. They do this by pushing a thin, flexible tube () through to the blocked artery in the lung. They can also use the to deliver a low-dose anticoagulant to the lungs (local thrombolysis). Medical professionals call this combined procedure “catheter-directed thrombolysis.”

After the acute treatment

People who’ve had pulmonary embolism usually stay in hospital a few days. Before you're discharged, the hospital will make sure your blood circulation is stable and you’re not having any problems with the anticoagulants. If the embolism was a mild case, it’s sometimes possible to go home after just one or two days.

You will have to take the anticoagulants for at least three months. It might be a good idea to take them for longer to prevent other embolisms in the future. You can talk to your doctor about the pros and cons of doing this.

Everyday life

Severe pulmonary embolism, in particular, is quite a dramatic thing to happen to you. People are often scared it might happen again. Some find it useful to return to their daily routine so they have a sense of structure and security again.

Physical symptoms that remind them of the pulmonary embolism (like a faster heartbeat or breathing problems) can be very frightening for them. Because of this, some people are scared to do physical exercise after having a pulmonary embolism. But many manage to distinguish between normal effects of exercise and medically concerning symptoms.

It can help to talk to someone about these fears and worries. You could, for instance, join a support group or seek psychological help to cope better with your anxiety.

Medication that prevents blood clots could also cause heavy bleeding, so some people have mixed feelings about taking it at first. They may change their lifestyle and avoid activities with a high risk of injury, for instance, to reduce the risk of bleeding.

The exhaustion and lack of energy that follow pulmonary embolism can have an additional impact on everyday life. Not knowing how long this will last can also be emotionally draining. One way to deal with the after-effects of pulmonary embolism is to do less overall or break tasks down into small parts.

Pulmonary embolism turns people’s whole lives upside down – especially if they’re young. Many suddenly realize they’re not invincible. Some feel "’different” and left out by their peers. It can be particularly hard for young people to avoid alcohol, which they have to because of the medication. Having to take medication every day may also be difficult for them.

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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. informedhealth.org 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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