A pulmonary embolism (PE) occurs when a blood clot blocks an artery in the lungs. Most pulmonary embolisms develop when part of a deep vein thrombosis (DVT), usually in a leg, breaks away and travels to the lungs. PE can be life-threatening and requires immediate medical assessment.
Symptoms
- Sudden or unexplained shortness of breath
- Chest pain or discomfort, often worse with a deep breath or cough
- Rapid breathing or a faster than normal heartbeat
- Cough, sometimes with blood
- Lightheadedness, weakness or fainting
A pulmonary embolism can occur without obvious symptoms of DVT. DVT symptoms may include swelling, pain or tenderness, warmth, redness or discoloration in one leg or arm.
When to seek emergency help
Seek emergency medical care immediately for sudden or severe breathing difficulty, unexplained chest pain with breathlessness, coughing up blood, fainting, collapse, or rapidly worsening symptoms. Use your local emergency medical service when symptoms are severe or life-threatening.
Risk factors
Risk can increase after major surgery, hospitalization, prolonged immobility or long-distance travel. Other risk factors include a previous DVT or PE, cancer, pregnancy and the period after childbirth, older age, obesity, certain inherited clotting disorders, serious injury and medicines containing estrogen.
Diagnosis
Symptoms of PE can resemble pneumonia, heart attack and other conditions, so diagnosis requires medical assessment and appropriate testing. Evaluation may include oxygen measurement, an electrocardiogram, blood tests such as D-dimer and imaging.
CT pulmonary angiography (CTPA) is the standard imaging test used to diagnose pulmonary embolism. A ventilation-perfusion (V/Q) scan may be used when CTPA is unsuitable. Ultrasound of the legs can help identify a DVT.
Treatment
Anticoagulant medicines are the main treatment for most people with PE. They reduce the blood’s ability to clot, helping prevent the existing clot from becoming larger and reducing the risk of new clots.
Severe or life-threatening PE may require thrombolytic treatment to dissolve the clot, catheter-based treatment or, in selected cases, surgery. Treatment decisions depend on severity, bleeding risk and overall health.
Anticoagulants can cause bleeding. Take them exactly as prescribed and seek medical advice for unusual or significant bleeding. Do not stop prescribed treatment without medical guidance.
Recovery and follow-up
The duration of anticoagulant treatment depends on why the clot occurred, the risk of another clot and the risk of bleeding. Follow-up is important because some people develop persistent breathlessness or, rarely, chronic thromboembolic pulmonary hypertension after PE.
Prevention may include early movement after illness or surgery, prescribed preventive anticoagulation for people at increased risk and individualized advice during prolonged travel.
Related topics
Sources and further reading
- CDC: Venous Thromboembolism
- CDC: Testing and Diagnosis for Venous Thromboembolism
- NHLBI: Pulmonary Embolism
- MedlinePlus: Pulmonary Embolism
Last reviewed: 4 September 2026.