Pulmonary Embolism Guide: Symptoms, Causes, Diagnosis, and Treatment
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
TL;DR
A pulmonary embolism (PE) is a blood clot that gets stuck in an artery in the lung and blocks blood flow to part of the lung. The clot most often forms in a deep vein of the leg — a condition called deep vein thrombosis (DVT) — and travels up through the right side of the heart into the lungs. A PE can be life-threatening: about one-third of people with an undiagnosed, untreated PE do not survive, but prompt treatment greatly reduces the risk of death. The warning signs are sudden shortness of breath, sharp chest pain, and fainting, and the standard treatment is blood-thinning medication (anticoagulants) that stops the clot growing while the body breaks it down.
Quick Answer
What is a pulmonary embolism? A blood clot stuck in an artery in the lung, blocking blood flow. It most often travels from a deep vein clot in the leg (deep vein thrombosis).
What are the warning signs? Sudden shortness of breath, sharp chest pain that worsens with a deep breath or cough, and fainting. Call for urgent care — a PE can be life-threatening.
Who is at higher risk? People with a personal or family history of clots, cancer, recent surgery, long bed rest or long trips, heart disease, clotting disorders, kidney disease, smoking, excess weight, estrogen therapy, or pregnancy.
How is it diagnosed? CT pulmonary angiography (3D imaging of the lung arteries) is the workhorse test; D dimer blood tests, leg ultrasound, V/Q scans, and pulmonary angiography round out the diagnostic toolkit.
How is it treated? Blood thinners (anticoagulants) are the cornerstone — they stop the clot from growing while the body dissolves it. Clot dissolvers, catheter clot removal, and vein filters are used in more serious or complicated cases.
What Is a Pulmonary Embolism?
A pulmonary embolism (PE) occurs when a blood clot gets stuck in an artery in the lung, blocking blood flow to part of the lung.
In most cases, the clot does not start in the lung at all. It begins in a deep vein of the leg — a condition called deep vein thrombosis (DVT) — and travels up through the right side of the heart into the lungs. Rarely, the clot forms in a vein in another part of the body.
A pulmonary embolism is a blood clot that blocks and stops blood flow to an artery in the lung.
Because one or more clots block blood flow to the lungs, a PE can be life-threatening. The encouraging fact is that prompt treatment greatly reduces the risk of death — which is why recognizing the symptoms and acting fast matters so much.
What Are the Warning Signs?
PE symptoms vary a great deal depending on how much of the lung is involved, the size of the clots, and whether underlying lung or heart disease is present. Three symptoms stand out as the most common.
Common symptom | What it looks like |
|---|---|
Shortness of breath | Usually appears suddenly; trouble catching your breath even at rest, and it gets worse with physical activity |
Chest pain | Often sharp and felt when breathing in deeply — it may feel like a heart attack; the pain can also appear when coughing, bending, or leaning over |
Fainting | You may pass out if your heart rate or blood pressure drops suddenly (this is called syncope) |
Several other symptoms can accompany a PE.
Other symptom | Notes |
|---|---|
Cough | May include bloody or blood-streaked mucus |
Heartbeat | Rapid or irregular |
Lightheadedness or dizziness | Can accompany the breathlessness |
Excessive sweating | Common in acute episodes |
Fever | Possible |
Leg pain or swelling | Usually in the back of the lower leg — a clue that a DVT is present |
Clammy or discolored skin | Called cyanosis |
When Should You Get Urgent Help?
A pulmonary embolism can be life-threatening, so this is one condition where speed matters more than certainty.
Seek urgent medical attention if you experience unexplained shortness of breath, chest pain, or fainting.
Do not wait to see whether the symptoms pass. The difference between prompt treatment and untreated PE is dramatic — which is explained in the complications section below.
What Causes a Pulmonary Embolism?
A PE occurs when a clump of material — most often a blood clot — gets stuck in an artery in the lungs, blocking blood flow. Most clots come from the deep veins of the legs (DVT).
In many cases, multiple clots are involved. The portions of lung served by each blocked artery cannot get blood and may die. This is called a pulmonary infarction, and it makes it harder for the lungs to supply oxygen to the rest of the body.
Occasionally, the blockage is caused by substances other than blood clots:
Non-clot cause | What it is |
|---|---|
Fat | From the inside of a broken long bone |
Tumor material | Part of a tumor breaking off |
Air bubbles | Trapped in the bloodstream |
Who Is at Higher Risk?
Although anyone can develop the blood clots that lead to a PE, several factors raise the odds considerably.
Risk factor | Why it raises risk |
|---|---|
History of blood clots | Personal or family (parent, sibling) history of venous clots or PE raises risk |
Cancer | Especially brain, ovary, pancreas, colon, stomach, lung, and kidney cancers, and cancers that have spread; chemotherapy increases risk further; tamoxifen or raloxifene (Evista) raises risk in people with a breast cancer history |
Surgery | One of the leading causes of problem blood clots; clot-prevention medicine is often given before and after major surgery |
Clotting disorders | Inherited conditions that make blood more likely to clot; kidney disease also raises risk |
COVID-19 | Severe symptoms increase PE risk |
Long bed rest | Blood flow slows and pools in the legs after surgery, heart attack, leg fracture, trauma, or serious illness |
Long trips | Sitting cramped on lengthy plane or car trips slows blood flow in the legs |
Smoking | Increases clot risk, especially alongside other risk factors |
Being overweight | Excess weight raises risk, particularly with other factors present |
Estrogen | Birth control pills and hormone replacement therapy increase clotting factors, especially in smokers or overweight people |
Pregnancy | The baby's weight pressing on pelvic veins slows blood return from the legs |
What Are the Possible Complications?
A pulmonary embolism can be life-threatening, and the untreated statistics are sobering: about one-third of people with an undiagnosed and untreated PE do not survive. When the condition is diagnosed and treated promptly, that number drops dramatically.
Complication | What happens |
|---|---|
Death | Untreated PE carries a one-in-three fatality rate; prompt treatment greatly reduces this |
Pulmonary hypertension | Blocked lung arteries force the heart to work harder to push blood through, raising pressure in the lungs and right side of the heart and eventually weakening the heart |
Chronic pulmonary hypertension | In rare cases, small clots remain in the lungs and scarring develops in the pulmonary arteries over time, restricting blood flow |
How Is a Pulmonary Embolism Diagnosed?
A PE can be difficult to diagnose — especially if underlying heart or lung disease is present. Doctors combine your medical history, a physical exam, and one or more imaging or blood tests.
Test | What it does |
|---|---|
Blood tests | Measure D dimer (a clot-dissolving substance; high levels suggest clots, though other factors can raise them too), blood oxygen and carbon dioxide levels, and whether an inherited clotting disorder is present |
Chest X-ray | Cannot diagnose a PE and may look normal even when one exists, but can rule out other conditions with similar symptoms |
Ultrasound (duplex scan) | Sound waves scan the veins of the thigh, knee, calf, and sometimes arms for deep vein clots; finding a leg clot often triggers immediate treatment |
CT pulmonary angiography | The workhorse PE test — CT scans create 3D images that find clots in the lung arteries; contrast dye is given through a vein in the hand or arm |
V/Q scan | A small dose of radioactive tracer maps blood flow (perfusion) against airflow (ventilation); used when CT radiation or contrast should be avoided; can show whether clots are causing pulmonary hypertension |
Pulmonary angiogram | The most accurate test — a catheter is threaded from the groin through the heart into the lung arteries with dye and X-rays; reserved for cases where other tests fail, because it requires high skill and carries risks including kidney damage from the dye |
MRI | Uses magnetic fields rather than radiation; usually reserved for pregnant people (to avoid radiation to the baby) and people whose kidneys could be harmed by dye |
How Is a Pulmonary Embolism Treated?
Treatment focuses on two goals: keeping the blood clot from getting bigger and preventing new clots from forming. Prompt treatment is essential to prevent serious complications or death.
Blood Thinners (Anticoagulants)
Anticoagulants are the cornerstone of PE treatment. They prevent existing clots from growing and new clots from forming while your body works to break the clots down on its own.
Heparin is a frequently used anticoagulant given through a vein or injected under the skin. It acts quickly and is often given alongside an oral anticoagulant such as warfarin (Jantoven) until the oral medicine becomes effective — a process that can take several days.
Newer oral anticoagulants work more quickly and have fewer interactions with other medicines. Some can be taken by mouth from the start, without needing heparin first. The one caution that applies to all anticoagulants: bleeding is the most common side effect.
Clot Dissolvers (Thrombolytics)
Clots usually dissolve on their own over time. Thrombolytics — clot-dissolving medicines given through a vein — can dissolve clots quickly, but because they can cause sudden and severe bleeding, they are usually reserved for life-threatening situations.
Surgical and Other Procedures
Procedure | When it is used |
|---|---|
Clot removal | A large, life-threatening clot is removed using a thin, flexible catheter threaded through the blood vessels |
Vein filter (IVC filter) | A catheter positions a filter in the inferior vena cava — the body's main vein running from the legs to the right side of the heart — to catch clots before they reach the lungs; used for people who cannot take anticoagulants or who form clots despite them; some filters can be removed later |
Ongoing Care
Because you may be at risk of another DVT or PE, treatment continues after the acute episode. Staying on anticoagulants, being monitored as often as your provider suggests, and keeping regular follow-up visits are all part of preventing or treating complications.
How Can Pulmonary Embolisms Be Prevented?
Preventing clots in the deep veins of the legs is the best protection against PE — which is why hospitals take clot prevention so seriously.
Hospital prevention measure | How it works |
|---|---|
Blood thinners | Given before and after surgery, and to hospitalized patients with conditions like heart attack, stroke, or cancer complications |
Compression stockings | Squeeze the legs steadily to help veins and leg muscles move blood more efficiently — a safe, simple, inexpensive way to stop blood pooling during and after surgery |
Leg elevation | Raising the bottom of the bed 4 to 6 inches (10 to 15 cm) with blocks or books is very effective |
Early movement | Getting up and moving as soon as possible after surgery prevents PE and speeds recovery overall |
Pneumatic compression | Thigh- or calf-high cuffs inflate and deflate every few minutes, massaging the veins and improving blood flow |
Preventing Clots While Traveling
The clot risk during travel is low but rises with the length of the journey. If you have risk factors, talk with your provider before a long trip. Practical steps include drinking plenty of water (alcohol contributes to fluid loss), walking around the cabin about once an hour or stopping to walk during long drives, bending your ankles and raising your toes every 15 to 30 minutes while seated, and wearing support stockings if recommended.
What to Expect at the Doctor
A pulmonary embolism is often first evaluated in a hospital, emergency room, or urgent care center — so if you think you might have one, seek medical attention right away.
Preparing for the visit goes faster if you bring a list: a detailed description of your symptoms, past medical problems (especially recent surgeries, injuries, or illnesses that kept you in bed for days), details of any recent long car or plane trips, all medicines including vitamins and supplements with doses, your parents' and siblings' medical problems, and your questions.
During the physical exam, expect the provider to examine your legs for signs of a deep vein clot — a swollen, tender, red, warm area — and to listen to your heart and lungs and check your blood pressure before ordering tests.
Conclusion
A pulmonary embolism is a medical emergency in disguise: a clot that quietly formed in a leg vein, broke free, and lodged in the lungs. Its warning signs — sudden breathlessness, sharp chest pain, fainting — deserve immediate action, not watchful waiting. The statistics are stark (untreated, a PE kills about one in three), but the flip side is genuinely hopeful: prompt diagnosis with CT imaging and prompt treatment with blood thinners dramatically cut the risk of death. Knowing your risk factors, moving regularly on long trips, and getting up early after surgery are simple steps that protect you long before any symptoms appear.
An inherited clotting disorder is one of the risk factors for pulmonary embolism — explore our related guide on Factor V Leiden for more, or read about Heart Attack symptoms and treatment, since PE chest pain can feel similar.
*This guide is for general information only and is not a substitute for professional medical advice. Always consult a qualified healthcare provider for diagnosis and treatment.*
Frequently Asked Questions
What exactly is a pulmonary embolism?
A pulmonary embolism (PE) is a blood clot stuck in an artery in the lung, blocking blood flow to part of the lung. It most often travels from a deep vein clot in the leg (deep vein thrombosis, or DVT).
What are the first warning signs?
Sudden shortness of breath — even at rest — is the most common sign. Sharp chest pain that worsens with a deep breath, cough, or bending, and fainting (syncope) are the other key warning signs that need urgent medical attention.
Can a pulmonary embolism be fatal?
Yes. About one-third of people with an undiagnosed, untreated PE do not survive. Prompt diagnosis and treatment dramatically reduce the risk of death, which is why urgent care matters.
What causes most pulmonary embolisms?
Blood clots that form in the deep veins of the legs (DVT) account for most cases. Rarely, clots form elsewhere, or the blockage is caused by fat, tumor material, or air bubbles.
Who is most at risk?
People with a personal or family clot history, cancer or chemotherapy, recent surgery, long bed rest or long trips, heart failure, inherited clotting disorders, kidney disease, severe COVID-19, smoking, excess weight, estrogen therapy, or pregnancy.
How is a PE confirmed?
CT pulmonary angiography — 3D CT imaging of the lung arteries — is the workhorse test. D dimer blood tests, leg ultrasound, V/Q scans, and pulmonary angiography (the most accurate test) are also used depending on the situation.
How is it treated?
Blood thinners (anticoagulants) are the cornerstone — they stop the clot growing while the body dissolves it. Clot dissolvers (thrombolytics) are used in life-threatening cases, and catheter clot removal or a vein filter (IVC filter) is used when blood thinners cannot be.
Can a pulmonary embolism be prevented?
Largely, yes — by preventing leg clots. Blood thinners, compression stockings, leg elevation, early movement after surgery, pneumatic compression, staying hydrated and moving on long trips all reduce the risk.
What This Guide Is Based On
Specialist-reviewed hospital clinical guidance on pulmonary embolism, updated December 2022, alongside the peer-reviewed second update of the CHEST antithrombotic therapy guideline (Chest, 2021), the pulmonary thromboembolism chapters in Murray and Nadel's Textbook of Respiratory Medicine (7th edition, 2022), Ferri's Clinical Advisor 2023, and the Agency for Healthcare Research and Quality's blood clot prevention and treatment guide.
References
Pulmonary embolism — Symptoms & causes — Mayo Clinic, updated December 1, 2022.
Pulmonary embolism — Diagnosis & treatment — Mayo Clinic, updated December 1, 2022.
Additional references consulted:
Stevens SM, et al. Antithrombotic therapy for VTE disease: Second update of the CHEST guideline and expert panel report. Chest, 2021.
Broaddus VC, et al., eds. Pulmonary thromboembolism: Presentation and diagnosis and Pulmonary thromboembolism: Prophylaxis and treatment. Murray and Nadel's Textbook of Respiratory Medicine, 7th ed., Elsevier, 2022.
Ferri FF. Pulmonary embolism. Ferri's Clinical Advisor 2023, Elsevier, 2023.
Agency for Healthcare Research and Quality, Your guide to preventing and treating blood clots.
Grillet F, et al. Acute pulmonary embolism associated with COVID-19 pneumonia. Radiology, 2020.
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