Pulmonary Embolism Symptoms: Warning Signs & How to Detect It

The most common symptoms of a pulmonary embolism are sudden shortness of breath, sharp chest pain that gets worse when you breathe in, a fast heartbeat or fast breathing, a cough (sometimes with a little blood), and lightheadedness or fainting. About 4 in 10 people also notice pain or swelling in one calf, where the clot usually started. If these come on suddenly, call 911.

A pulmonary embolism (PE) is a blood clot that lodges in an artery of the lung. It is common, it is treatable, and it is also one of the easiest serious conditions to miss, because its warning signs overlap with a heart attack, pneumonia, a panic attack or a pulled muscle. The CDC estimates that up to 900,000 Americans have a blood clot in a vein each year, and in about a quarter of people with a PE, sudden death is the first sign. Knowing what the early symptoms of a pulmonary embolism actually look like, including the ones that are easy to brush off, is how you catch it in time.

This guide walks through each warning sign, how often it really shows up, how PE differs from look-alike conditions, and what doctors do to confirm or rule it out.

What Happens in Your Body During a Pulmonary Embolism

Most PEs begin as a deep vein thrombosis (DVT), a clot in a deep vein of the calf, thigh or pelvis. A piece breaks off, rides through the right side of the heart and gets stuck in the pulmonary circulation, the network of arteries that carries blood to the lungs to pick up oxygen.

Think of it like a fallen tree across one lane of a highway. Air still reaches that part of the lung, but blood can’t get past the blockage, so gas exchange between the air sacs and capillaries breaks down. Your brain senses the problem and makes you breathe faster. If the clot is big enough, pressure backs up into the right side of the heart, which has to pump against the blockage. That strain on the heart and pulmonary artery is what makes a large PE dangerous, and it explains symptoms like a racing pulse, fainting and low blood pressure.

That is also why symptoms vary so much. A small clot in a far branch of the lung may cause only a stitch-like pain when breathing. A large clot near the center can cause collapse within minutes.

The Most Common Symptoms of a Pulmonary Embolism

The numbers below come from PIOPED II, a large NIH-funded study that recorded the symptoms of 192 adults with a confirmed PE. They give a much more honest picture than most symptom lists, because they show how often each sign actually appears.

1. Sudden shortness of breath (about 79%)

This is the hallmark symptom. People describe it as not being able to get a full breath, or feeling winded after walking across a room. In about two-thirds of cases it starts within seconds or minutes. It can happen at rest, and it often gets worse with any activity. Around 1 in 6 people only notice it when they exert themselves, and some find it hard to breathe lying flat.

2. Fast breathing (about 57%)

A breathing rate of 20 or more breaths per minute at rest is common. Family members often notice this before the patient does.

3. Sharp chest pain that’s worse when you breathe in (about 47%)

Doctors call this pleuritic chest pain. It usually feels sharp or stabbing, sits on one side of the chest or under the ribs, and catches you at the top of a deep breath, a cough, or when you bend over. It can also be felt in the back or shoulder. A dull, pressure-like pain is less typical but happens too, especially with larger clots that strain the heart.

4. Cough (about 43%)

The cough is usually dry. Some people bring up pink-tinged or blood-streaked mucus. Coughing up blood was actually uncommon in PIOPED II (around 6% of patients), and when it happened the amount was small, usually less than a teaspoon.

5. Pain or swelling in one leg (about 4 in 10)

Calf or thigh pain was reported by 42% of patients and swelling by 39%. The leg may feel tight, cramp-like, warm or tender, and it may look red or larger than the other one. This is the DVT that fed the PE. One swollen, sore calf plus new breathlessness is a combination you should never ignore.

6. Racing heart (about 26%)

A resting heart rate above 100 beats per minute, or a pounding or fluttering feeling (palpitations), happens because the heart is working harder to push blood through blocked vessels.

7. Lightheadedness, fainting or collapse (less common, but the most serious)

About 8% of patients in PIOPED II presented with fainting or a dangerously low blood pressure. Fainting suggests a large clot that is limiting blood flow to the left side of the heart. Treat it as a 911 emergency every time.

Other symptoms that can occur

• Wheezing (about 31%), which can lead to a mistaken asthma diagnosis
• Sweating, clammy skin, or a sense that something is badly wrong
• A low-grade fever
• Arm swelling, if the clot started in an arm vein (more common with a PICC line or central catheter)

Warning Signs People Expect but Often Don’t Have

Many symptom lists put blue lips and coughing up blood near the top. In practice, people waiting for those “classic” signs can lose precious time. Here is what the research shows:

• Blue lips or skin (cyanosis) is rare. It appeared in about 1% of PIOPED II patients. When it does occur, it signals a severe PE.
• Most people do not have a racing pulse. Only about 1 in 4 had a heart rate over 100.
• Oxygen levels can look normal. Roughly 1 in 3 patients had a normal blood oxygen level on an arterial blood test. A normal reading on a home pulse oximeter is not reassurance.
• Symptoms don’t always start suddenly. In about 19% of people, breathlessness built over several days, which is easy to blame on a cold, being out of shape or anxiety.
• Older adults may have fewer clues. People 70 and older reported chest pain and leg swelling less often than younger patients.

Some small clots cause no symptoms at all and are found by chance on a scan for something else. If you want to understand that scenario better, see how long you can have a pulmonary embolism without knowing.

The flip side is reassuring: in PIOPED II, 97% of patients had at least one of four findings, namely shortness of breath, fast breathing, pleuritic chest pain, or signs of a leg clot. That short list is your best everyday screen.

How Symptoms Change With the Size of the Clot

Doctors classify PE by its effect on the heart and blood pressure rather than by the clot’s size alone. This table shows what each level tends to look like.

Risk level	What it means	Typical symptoms
Low risk (small PE)	Clot in a smaller branch; heart and blood pressure normal	Sharp pain on breathing, mild breathlessness, cough, sometimes no symptoms
Intermediate risk (submassive)	Blood pressure normal, but the right side of the heart is strained	Clear breathlessness at rest, fast pulse, fatigue, chest pressure
High risk (massive)	Systolic blood pressure below 90 mm Hg, or a drop of 40 mm Hg or more	Fainting, confusion, cold clammy skin, severe breathlessness, collapse

Risk level guides how aggressively a PE is treated. Our guide to how a pulmonary embolism is treated explains the options at each stage, and how a pulmonary embolism can become fatal covers what happens when the heart can’t keep up.

Pulmonary Embolism vs. Heart Attack, Pneumonia and Panic Attack

No single symptom proves a PE, which is why doctors rely on tests. Still, a few patterns can help you describe what you’re feeling.

Feature	Pulmonary embolism	Heart attack	Pneumonia	Panic attack
Chest pain	Sharp, worse with deep breaths	Pressure or squeezing, may spread to arm or jaw	Sharp with breathing or coughing	Tight or aching, often central
Onset	Usually sudden	Sudden or over minutes	Gradual, over days	Sudden, peaks within 10 minutes
Fever	Uncommon, low-grade	Rare	Common, often high	No
Cough	Dry, sometimes blood-streaked	Uncommon	Productive, colored phlegm	No
Leg pain or swelling	Often, one leg	No	No	No
Recent trigger	Surgery, travel, bed rest, pregnancy, cancer	Exertion, stress	Recent cold or flu	Stress, but can be unprovoked

A panic attack is a diagnosis of exclusion. If this is your first episode, or you have any risk factors for clots, get checked rather than assuming it’s anxiety.

Who Should Watch Most Closely for PE Symptoms

More than 9 in 10 people in PIOPED II had at least one known risk factor. Take new breathlessness or chest pain especially seriously if any of these apply:

• A recent hospital stay or surgery. More than a third of clots are linked to a recent hospitalization, and most appear after the patient has gone home. Hip and knee replacements carry particular risk.
• Bed rest or immobility for 3 days or more, a leg cast, or travel lasting longer than 4 hours.
• Cancer and its treatment. About 1 in 5 clots is related to cancer, with the highest risk in the first few months after diagnosis.
• Pregnancy and the 3 months after delivery. The risk of a clot is about five times higher, and PE is a leading cause of pregnancy-related death in the US.
• Estrogen in birth control pills, patches, rings or hormone therapy.
• A previous DVT or PE, or a family history of clots or an inherited clotting disorder.
• Obesity, smoking, heart failure, a central venous line, and recent serious infection, including severe COVID-19.

For a sense of how many people are affected, see how common pulmonary embolism is.

How Doctors Detect a Pulmonary Embolism

You can recognize the warning signs, but only medical testing can confirm a PE. In the emergency department, the process usually follows these steps:

1. Estimate the probability. The doctor uses a scoring tool such as the Wells score or Geneva score, which adds up points for things like leg-clot signs, heart rate over 100, recent surgery, coughing up blood and cancer.
2. Apply the PERC rule if the risk is low. If you are under 50, have a heart rate below 100, oxygen saturation of 95% or higher, and none of the other five rule-out items, PE is unlikely enough that no further testing is needed.
3. Check a D-dimer blood test. D-dimer is a fragment released when clots break down. A normal result in a low- or moderate-risk person effectively rules out a PE. A high result is not proof, because infection, pregnancy, surgery and age all raise it. For people over 50, many hospitals use an age-adjusted cutoff (age × 10), so a 70-year-old’s threshold is 700 ng/mL.
4. Get a CT pulmonary angiogram (CTPA). This contrast-dye CT scan is the main test. It shows the clot directly and can also show strain on the right side of the heart.
5. Use a V/Q scan when CT isn’t suitable. A ventilation-perfusion scan is often preferred in pregnancy, severe kidney disease or a contrast allergy.
6. Add supporting tests. A leg ultrasound can find the DVT. An ECG, echocardiogram, troponin and BNP blood tests help judge how hard the heart is working and rule out other causes.

The StatPearls review of acute pulmonary embolism describes this pathway in detail for clinicians. For a patient-friendly walk-through, read how a pulmonary embolism is diagnosed and how doctors rule out a pulmonary embolism.

What to Do If You Think You Have a Pulmonary Embolism

1. Call 911 for sudden shortness of breath, chest pain, fainting, or coughing up blood. Don’t drive yourself, and don’t wait to see if it passes.
2. Stop moving and sit upright while you wait. Avoid rubbing or massaging a painful, swollen leg.
3. Note when symptoms began and whether they started suddenly or gradually.
4. Gather key information: recent surgery, travel, hospital stays, pregnancy, cancer treatment, and a list of your medications, especially hormones or blood thinners.
5. Don’t take leftover blood thinners or anyone else’s medication. Treatment needs to be guided by test results.

When to See a Doctor

Call 911 or go to the nearest emergency department now if you have:

• Sudden or rapidly worsening shortness of breath
• Chest pain, especially if it is sharp and worse when you breathe in
• Fainting, near-fainting or confusion
• Coughing up blood
• Any of the above together with a swollen or painful leg

Call your doctor the same day if you have: new pain, swelling, warmth or redness in one leg or arm without breathing symptoms. This could be a DVT, and treating it early can stop a PE before it starts.

Book a follow-up visit if: you have already been treated for a PE and are still short of breath after about 3 months. Lingering breathlessness can be part of normal recovery, but it can also point to chronic thromboembolic pulmonary hypertension (CTEPH), which affects up to about 5% of survivors and is classed among the groups of pulmonary hypertension. Our article on how long a pulmonary embolism lasts explains what a typical recovery looks like.

If you need a lung specialist for evaluation or follow-up care, you can find a pulmonologist near you or browse pulmonologists who treat pulmonary embolism.

Frequently Asked Questions

What are the first signs of a pulmonary embolism?

The earliest signs are usually sudden shortness of breath and sharp chest pain when breathing in. Some people first notice a sore, swollen calf a few days before breathing symptoms start, which is the original leg clot.

Can pulmonary embolism symptoms come and go?

Breathlessness may feel better at rest and worse with activity, so it can seem to fluctuate. True PE symptoms don’t go away for good on their own, though, and repeated small clots can cause episodes over days or weeks. Symptoms that keep returning still need urgent testing.

Can you have a pulmonary embolism and not know it?

Yes. Small clots may cause mild or no symptoms and are sometimes found by chance on a CT scan. Mild breathlessness that builds over several days is also easy to dismiss. For more detail, see how you know if you have a pulmonary embolism.

Where do you feel pain from a pulmonary embolism?

Most often on one side of the chest or under the ribs. Some people feel it in the upper back or shoulder. It typically sharpens when you breathe deeply, cough or bend over, which helps tell it apart from muscle strain that hurts mainly when you move a certain way.

Can you walk around with a pulmonary embolism?

Many people with a smaller PE can walk and even go to work, which is one reason it gets missed. Being able to walk doesn’t mean the clot is harmless. If you have symptoms, get evaluated before deciding it’s safe to carry on.

Does a normal pulse oximeter reading rule out a pulmonary embolism?

No. About a third of patients in a large study had normal blood oxygen when they were diagnosed. A home oxygen reading can’t replace a D-dimer test or a CT scan.

How long can a pulmonary embolism go untreated?

There’s no safe waiting period. Without treatment, about 30% of people with a PE die, compared with about 8% who are treated promptly. Most PE deaths happen early, so speed matters. Learn more about survival and outlook after a pulmonary embolism and the most common causes of death in pulmonary embolism.

Want to explore more? Browse our full pulmonary embolism guides, including common myths about curing a PE. The NHLBI also has a clear overview of blood clot symptoms, and Mayo Clinic summarizes pulmonary embolism symptoms and causes.

References

1. Stein PD, Beemath A, Matta F, et al. Clinical characteristics of patients with acute pulmonary embolism: data from PIOPED II. Am J Med. 2007;120(10):871-879. PMC2071924
2. Vyas V, Sankari A, Goyal A. Acute Pulmonary Embolism. In: StatPearls. Updated December 11, 2024. NBK560551
3. Centers for Disease Control and Prevention. Data and Statistics on Venous Thromboembolism. Updated January 27, 2025. cdc.gov
4. National Heart, Lung, and Blood Institute. Venous Thromboembolism: Symptoms. nhlbi.nih.gov
5. Mayo Clinic Staff. Pulmonary embolism: Symptoms and causes. mayoclinic.org
6. Konstantinides SV, Meyer G, Becattini C, et al. 2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the European Respiratory Society. Eur Respir J. 2019;54(3).

This article is for general education and is not a substitute for advice from your doctor.