Pulmonary embolism

What is a pulmonary embolism and what are the symptoms?

On this page we explain what a pulmonary embolism is, what the common symptoms are and when you should seek medical help.

What is a pulmonary embolism?

A pulmonary embolism happens when a blood vessel in your lungs becomes blocked. Most of the time, this blockage is caused by a blood clot and happens suddenly.

It can be very serious because it can stop blood going to your lungs. Fast medical treatment can be lifesaving.

Call 999 if:

  • you have severe breathing difficulty or
  • your heart is beating very fast or
  • someone has passed out 

These could be signs of a pulmonary embolism or another serious condition.

What’s the difference between acute and chronic pulmonary embolism? 

An acute pulmonary embolism is when there’s a sudden blockage in the blood vessel in the lungs. Our information is focused on acute pulmonary embolism.

A chronic pulmonary embolism is when the blood vessels in the lungs have been blocked for a longer period of time. Most commonly it occurs because previous blood clots haven’t dissolved completely after an acute pulmonary embolism. A significant amount of clot remains in approximately 2% of patients (1 in 50) following an acute pulmonary embolism, leading to increased pressure within the lungs. This condition is called chronic thromboembolic pulmonary hypertension (CTEPH).

What are the symptoms of a pulmonary embolism?

The symptoms of a pulmonary embolism vary between different people and how large the clot is. Sometimes a small pulmonary embolism may cause no symptoms at all. The symptoms of a blood clot to the lungs are also seen in other lung conditions.

The main symptoms of a pulmonary embolism are:

  • chest pain
  • feeling short of breath
  • difficulty breathing
  • coughing up blood
  • feeling faint or even passing out.

Most pulmonary embolisms are caused by deep vein thrombosis (when a blood clot develops in a deep vein in the body, usually in the leg). So, another warning sign can be a painful, red or swollen leg (usually the calf). You can read more about what DVT looks like on the NHS website.

See a GP if:

  • you feel pain in your chest or upper back
  • you have difficulty breathing
  • you’re coughing up blood
  • you have pain, redness and swelling in one of your legs (usually the calf)

Read next: Causes and risk factors

 Download our pulmonary embolism information (PDF, 385 KB)

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