Hematologist
CION Cancer Clinics
Pulmonary embolism: recognising a clot in the lungs | CION Cancer Clinics
Sudden breathlessness, chest pain that is sharper when you breathe in, coughing up blood, a racing heart or fainting can mean a pulmonary embolism, a blood clot in the lungs. Call 108 or go to the nearest emergency department now. This page lists the signs, what the family should do while waiting, what the hospital will check, and what a symptom list cannot tell you. At CION Cancer Clinics, our haematologist cares for anaemia, bleeding, clotting and inherited blood disorders, with ArogyaSri, CGHS and cashless insurance accepted.
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Medically reviewed by Dr. Basudev PokhrelConsultant Haematologist · last reviewed September 2026, next review due September 2027
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On this page
- What are the warning signs of a clot in the lungs?
- How does a pulmonary embolism show itself?
- What should the family do while waiting for the ambulance?
- What happens once you reach the hospital?
- What do people often believe about breathlessness and clots?
- Who is at risk, and what can this page not tell you?
- Common questions about pulmonary embolism
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Do this first
If someone has sudden breathlessness, chest pain that is sharper when they breathe in, coughs up blood, or collapses, call 108 or go to the nearest emergency department now. This is more urgent still if they have a swollen leg, recent surgery, cancer or a past clot. Do not drive them yourself if an ambulance can come, and do not wait to see if it passes.
The short answer
What are the warning signs of a clot in the lungs?
The main signs of a pulmonary embolism are sudden breathlessness and chest pain that gets worse when you breathe in. Some people also cough up blood, feel their heart racing, or faint. Any of these is an emergency.
What is happening inside the body
A pulmonary embolism, often shortened to PE, is a blood clot that blocks an artery in the lungs. Most start as a clot in a deep leg vein, called a DVT, which breaks free and travels up through the heart. The blocked artery stops part of the lung getting blood, so less oxygen reaches the body, and the heart has to work much harder.
Why speed matters so much
A large clot can strain the heart suddenly and be life-threatening. Treatment given quickly stops the clot growing and prevents new ones. Emergency teams have the scans and medicines to confirm it and act on it. A clinic appointment next week, or a call to a family doctor, is the wrong place to start.
Signs can be mild. Breathlessness that is new and unexplained still needs the emergency department, even without chest pain.Not sure whether this applies to you?
Ask an oncologistWhat to look for
How does a pulmonary embolism show itself?
No single sign is always present. What families most often describe is someone who was fine, then suddenly was not.
Breathlessness
It usually comes on suddenly, even at rest, and may get worse with the smallest effort. Some people cannot finish a sentence.
Chest or upper back pain
Often sharp and stabbing, and worse on a deep breath or a cough. It is easily mistaken for a heart attack or gas.
Coughing up blood
Streaks of blood in the phlegm, or pink frothy spit. This always needs to be seen urgently.
Fast heartbeat, dizziness, fainting
The heart races to make up for the lost oxygen. Lips or fingers may look blue or grey. Collapse is a sign of a large clot.
Signs of a leg clot too
- One calf or thigh swollen
- Ache, warmth or darker skin on that leg
Before help arrives
What should the family do while waiting for the ambulance?
Sit them up and keep them still
Help the person into the position where breathing feels easiest, usually sitting upright. Loosen tight clothing. Do not make them walk to the car or climb stairs if you can avoid it.
Gather the medicines and reports
Put every current medicine, including any blood thinner, in a bag. Add recent discharge summaries, cancer treatment papers and any scan reports. Do not give extra doses of anything.
Note the facts the doctor will ask
When it started, any recent surgery, hospital stay, long journey, pregnancy or delivery, a swollen leg, and any past clots in the person or the family.
If they collapse
If they stop responding and are not breathing normally, tell the 108 call handler at once. They will guide you through what to do until the ambulance arrives.
Leave a number, we will call you
One field. No form to fill in, and no charge for the call.
In the emergency department
What happens once you reach the hospital?
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Oxygen and first checks
Oxygen levels, pulse and blood pressure are checked straight away. Oxygen is given if levels are low. An ECG, a heart tracing, helps rule out a heart attack.
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Blood tests
A D-dimer test may be done, along with kidney function and a blood count. A raised D-dimer does not prove a clot. It means more tests are needed.
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A scan of the lungs
Usually a CT pulmonary angiogram, a CT scan with dye that shows the lung arteries. When dye is unsuitable, such as with some kidney problems or in pregnancy, a different lung scan may be used.
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Treatment
Most people start a blood thinner. For a large clot straining the heart, a stronger clot-dissolving medicine or a procedure may be considered. The treating team weighs this against bleeding risk.
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Admission or home
Many people are admitted for monitoring. Some with a small clot and stable readings are sent home with close follow-up.
Commonly believed
What do people often believe about breathlessness and clots?
"It is only gas or acidity. Let us wait till morning."
Sharp chest pain with sudden breathlessness should never be treated at home as gas. Only tests can tell a clot, a heart attack and acidity apart. Waiting overnight is the delay that causes harm.
"There was no leg pain, so it cannot be a clot."
Many people with a pulmonary embolism never noticed a leg clot. The leg clot may have caused no signs, or the clot may have started somewhere else. The breathing signs are enough to act on.
"He is already on a blood thinner, so it cannot be a clot."
Clots can still form on treatment, especially with cancer or if doses were missed. Tell the emergency team about the blood thinner, and let them decide what to do with it.
"Once discharged, the danger is over, so we can stop the tablets."
Treatment usually continues for months after leaving hospital. Stopping on your own raises the chance of another clot. Only your treating team should change or stop a blood thinner.
Being straight with you
Who is at risk, and what can this page not tell you?
Anyone can have a pulmonary embolism, but the chance is higher after major surgery or a long stay in bed, during cancer and its treatment, in pregnancy and the weeks after delivery, on hormone tablets, and in people who have had a clot before or have an inherited clotting tendency.
A symptom list is not a diagnosis
Breathlessness and chest pain have many causes, including heart attacks, pneumonia, asthma and panic attacks. This page cannot tell you which one is happening. It can only tell you that these signs belong in an emergency department, where a scan gives the answer.
It cannot tell you your outlook
How someone recovers depends on the size of the clot, how the heart coped, the cause, and their other health conditions. Your treating team and haematologist are the right people to explain your own picture.
After a clot, who looks at the cause?
If a clot had no clear trigger, came back, or happened during cancer treatment, a haematologist review helps. CION's haematology team reviews reports, discusses complex cases at a tumour board and coordinates further tests with qualified centres.
Questions we are asked
Common questions about pulmonary embolism
Should I call 108 or take them to hospital by car?
Call 108 if the person is very breathless, has collapsed, looks grey or blue, or is confused. An ambulance can give oxygen on the way. If the signs are milder and an ambulance will take long, go by car to the nearest emergency department, with someone else driving.
How is a pulmonary embolism different from a heart attack?
Both can cause chest pain and breathlessness. Heart attack pain is often a heavy pressure that may spread to the arm or jaw. Clot pain is often sharp and worse on breathing in. The overlap is large, so do not try to decide at home. Both need the emergency department.
Can a pulmonary embolism come on slowly?
Yes. Some people notice breathlessness that creeps up over days, with tiredness or a cough, especially with smaller clots. New breathlessness that has no clear reason, and is getting worse, still needs same-day assessment, particularly if you have cancer, a recent operation or a swollen leg.
Is the CT scan with dye safe?
For most people, yes, and the benefit of finding a clot is large. Tell the team about kidney problems, diabetes medicines, any past reaction to dye, and pregnancy. If dye is not suitable, they may choose another lung scan or an ultrasound of the legs.
I have cancer. Is my risk of a clot higher?
Yes. Cancer itself, some chemotherapy and hormone treatments, surgery, central lines and long spells in bed all raise the chance. It does not mean a clot will happen. It does mean you should act quickly on new breathlessness or a swollen limb, and tell the doctor you are having cancer treatment.
Will I need blood thinners afterwards?
Almost always, for a period your doctor sets. The length depends on whether there was a clear trigger, your bleeding risk, and conditions such as cancer. Some people need longer treatment. Do not change or stop the medicine yourself, and ask your team when it will be reviewed.
Why am I still breathless after going home?
Tiredness and some breathlessness can linger while the lungs recover, and many people improve slowly. Breathlessness that is getting worse, new chest pain, or coughing up blood is not normal recovery. Go back to the emergency department, and mention the recent clot.
Should my family be tested for a clotting disorder?
Not routinely. Testing is useful only for some people, such as a clot with no clear cause at a young age or a strong family history. A haematologist can tell you whether testing would change anything. Ask them before arranging tests privately.
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Dr. Basudev Pokhrel reviews blood counts, transfusion needs and blood disorders, and works with the CION tumour board on blood cancers.
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Addressed by landmark, because that is how this city navigates. A haematology consultation can be booked at any of these centres through one helpline, and your team will tell you where each test or treatment takes place.
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Sources
- NHS — Pulmonary embolism
- NHLBI — Venous thromboembolism
- American Society of Hematology — Blood clots
- NICE — Venous thromboembolic diseases: diagnosis, management and thrombophilia testing (NG158)
This page is general information, not a prescription. Do not change or stop any treatment based on what you read here. If anything is worrying you, contact your own treating team — or call our helpline and we will help you reach the right specialist.
Keep reading
Related pages
DVT Explained: Symptoms and UrgencyThe leg clot that most lung clots start fromCancer-Associated ThrombosisClots during cancer treatmentHow Long to Stay on Blood ThinnersWhat decides how long treatment lastsThrombophilia Testing: Who Actually Needs ItWhether you or your family need clotting testsClotting, Thrombosis and AnticoagulationThe full guide to clots and blood thinners
Talk to us
Recovering from a clot and unsure what comes next?
Send us your discharge summary and scan reports. Our haematology team will help you understand them and plan follow-up. In an emergency, call 108 first.