Coughing Up Blood (Haemoptysis): Causes from Minor to Serious and When to Seek Urgent Care

It usually happens over a bathroom sink. A cough that has been rattling around for a fortnight finally brings something up, and there it is: a thin red thread laced through the phlegm, or a few rusty flecks on a tissue. The mind does not wait for evidence. It goes straight to the worst chapter of the medical textbook.

Here is the thing worth knowing before the panic sets in. Airway linings are delicate, richly supplied with blood, and easily bruised by weeks of coughing or by the inflammation of a chest infection. A speck of blood in sputum is one of the more common reasons people ring a nurse line, and the story behind it is often ordinary.

Often is not always. The same symptom can be the first visible sign of a clot, an infection that needs treating, or a growth in the airway. This article walks through how clinicians tell those apart, which details matter, and exactly when the sink is the wrong place to be.

What counts as coughing up blood, and what doesn't?

Hemoptysis is the medical term for blood that comes from the lungs or the breathing tubes (the bronchi and trachea) and is coughed out. The British spelling, haemoptysis, describes the same thing. It ranges from pink-tinged froth and red streaks in phlegm to frank red blood, and the amount matters far more than the color.

Two look-alikes get mistaken for it constantly. The first is blood from the nose or the back of the throat that trickles down and is then coughed or spat out; clinicians sometimes call this pseudohemoptysis. The second is blood vomited from the stomach or esophagus, which tends to be dark, coffee-ground brown and arrives with nausea rather than a cough. Both can look alarming on a tissue, and neither is a lung problem.

Why does the distinction matter so much? Because the lungs have an unusual blood supply. Most of the lung tissue is fed by low-pressure vessels, but the airway walls themselves are served by bronchial arteries that run at the same high pressure as the rest of the body. When those airway vessels are inflamed, stretched or eroded, they can bleed briskly. That is why even modest airway bleeding is treated seriously, and why the first job in any clinic is to work out where the blood is actually coming from.

Can coughing up blood be nothing serious?

Yes, and frequently it is. The NHS puts it plainly: coughing up blood is not usually a sign of a serious problem if you are young and otherwise healthy, though it is more concerning in older people and in those who smoke. Mayo Clinic notes that blood-tinged sputum is common in many minor respiratory conditions, and that bronchitis and bronchiectasis are the most frequent explanations overall.

Picture the lining of a bronchial tube after two weeks of hacking. It is swollen, raw and swept by air moving at speed several hundred times a day. Tiny surface vessels rupture the same way a scraped knee weeps. The blood is bright, the quantity is tiny, and it stops once the cough settles.

The catch is that nobody can tell from the tissue alone whether they belong to the reassuring group. A single streak in a healthy 25-year-old with a cold has a very different weight from the same streak in a 65-year-old who has smoked for four decades or who has lost weight without trying. Context, not color, does the sorting.

So the honest answer has two halves. Small amounts of blood in phlegm are often harmless and self-limiting. Every episode still warrants a conversation with a clinician, because the harmless causes and the serious ones can look identical at the start, and the serious ones are far easier to deal with when caught early.

How do you know if blood is from your throat or lungs?

Doctors ask a set of small, practical questions to locate the source, and you can ask them of yourself while you wait to be seen. Did it come up with a cough, or did you spit or vomit it? Is it frothy? Is your nose stuffy or crusted? Did the color look like fresh paint or like old coffee grounds?

The pattern below summarizes what clinicians generally look for. It is a guide, not a verdict; mixed pictures are common, and the examination and tests decide.

Feature	Lungs or airways (hemoptysis)	Nose or throat	Stomach (vomited blood)
How it arrives	With a cough	Spat out, post-nasal drip, after blowing nose	With vomiting or retching
Appearance	Bright red, often frothy, mixed with phlegm	Bright red, thin, sometimes clots from nostrils	Dark red to brown, coffee-ground texture
Companion symptoms	Cough, breathlessness, chest discomfort	Nasal congestion, sore throat, nosebleed history	Nausea, abdominal pain, black stools
Timing	Any time; sometimes worse on waking	Often after sleep or in dry air	After meals, alcohol or stomach upset

One useful clue: froth. Air mixed into blood as it is coughed up gives it a bubbly quality that vomited blood rarely has. Another: check the nostrils and the back of the throat in a mirror. Dried blood or a raw patch there points away from the lungs. When in doubt, describe exactly what you saw to the clinician and let them decide; there is no prize for guessing right.

Coughing up blood causes: the common ones first

The list of conditions that can produce blood in phlegm is long, but most cases in general practice trace back to a handful of causes. MedlinePlus, the NHS and Mayo Clinic all put airway irritation and infection at the top.

• Prolonged coughing from a cold, flu or post-viral cough, which bruises the airway lining.
• Acute bronchitis or a chest infection, where inflamed bronchial walls bleed into the mucus.
• Pneumonia, particularly when the sputum turns rust-colored.
• Bronchiectasis, a long-term widening and scarring of the airways that makes them prone to infection and bleeding.
• Chronic obstructive pulmonary disease (COPD), especially during a flare-up.

Behind these sit the less common but more consequential causes: pulmonary embolism, tuberculosis and other serious infections, lung cancer, and, more rarely, inflammatory vessel disorders, bleeding tendencies and heart conditions that raise pressure in the lung vessels. Trauma to the chest and inhaled irritants such as cocaine also appear on the list.

The frequency ranking shifts with the person in front of the doctor. In a smoker over 40 with weight loss, cancer moves up the list even though it remains uncommon overall. In someone who has just come back from a long flight with a swollen calf, a clot leaps to the front. In a recent immigrant from a region where tuberculosis is common, or someone who has spent time in a shelter or prison, TB has to be considered. Good medicine is less about memorizing the list than about reading which parts of it apply to you.

Why a chest infection or bronchitis makes phlegm streak red

Bronchitis is inflammation of the tubes that carry air into the lungs. During an infection, the lining swells, produces extra mucus and becomes packed with fragile new blood vessels as part of the healing response. A hard cough then does two things at once: it tears those vessels and it sweeps the mucus, now tinged pink or streaked red, up into the mouth.

The result is usually small in volume, mixed through yellow or green sputum rather than pure, and it tends to follow a recognizable arc. It appears a week or two into the illness, when the cough is at its most violent, and fades as the cough eases. Fever, aching and a feeling of tightness in the chest often keep it company.

Pneumonia can look similar but sits a rung higher on the concern ladder. Infection deep in the lung tissue can produce sputum with a rusty, brownish tone, alongside fever, breathlessness and sometimes sharp chest pain on breathing in. That pattern deserves prompt assessment rather than a wait-and-see approach.

Timelines help. The NHS advises seeing a GP for any cough lasting more than three weeks, regardless of whether blood is present. A cough that outlives the infection that started it, or blood that appears after the fever has gone, should prompt a rethink rather than reassurance. Recovery from a simple chest infection is a story that moves in one direction; when it stalls or reverses, the diagnosis needs revisiting.

Bronchiectasis: the frequent cause most people have never heard of

Ask a room of non-medical people what causes coughing up blood and almost nobody will say bronchiectasis. Ask a chest physician and it will be among the first words out of their mouth. The condition involves permanent widening of some of the airways, usually after past infections or long-standing inflammation. The stretched tubes lose their ability to clear mucus efficiently, secretions pool, bacteria settle in, and the cycle of infection and inflammation repeats.

Those damaged airway walls carry enlarged, fragile bronchial arteries lying close to the surface. Every flare-up irritates them, and blood appears in the sputum, sometimes as streaks and occasionally in larger amounts. The NHS lists bronchiectasis as one of the more common causes of coughing up blood, and its hallmark is not the blood itself but the company it keeps: a daily productive cough over months or years, recurrent chest infections, and breathlessness that slowly creeps in.

Diagnosis rests on a detailed CT scan of the chest, which shows the widened airways directly; a standard chest X-ray can miss it. Management focuses on clearing mucus with physiotherapy techniques, treating infections promptly and identifying any underlying cause, decisions that belong with the treating clinician.

Why single this out? Because a person with bronchiectasis may cough up blood periodically for years, and each episode can trigger fresh anxiety. Knowing the diagnosis changes the experience entirely: the same red streak becomes a familiar signal to check in with the care team rather than a mystery to dread.

Could it be a blood clot in the lung?

A pulmonary embolism is a clot, usually formed in a leg vein, that travels to the lungs and lodges in a lung artery. It blocks blood flow to a section of lung tissue, which can become inflamed or damaged and bleed into the airways. The NHS lists it among the causes of coughing up blood that need urgent attention.

What sets a clot apart from an infection is the cast of accompanying symptoms and how fast they arrive. Breathlessness that comes on suddenly, sharp chest pain that worsens when breathing in, a racing heart and light-headedness are the classic set. Fever is usually absent or mild. Look at the legs as well: a swollen, warm, painful calf on one side points strongly toward a clot that may have already sent fragments upward.

Risk factors matter here more than almost anywhere else in this article. Recent surgery, a long period of immobility such as a hospital stay or a lengthy flight, pregnancy or recent delivery, active cancer, certain hormone treatments and a personal or family history of clots all raise suspicion. A clinician who hears “coughing up blood” alongside any of these will move quickly.

Confirming the diagnosis typically involves blood tests, scans of the lung arteries and sometimes ultrasound of the leg veins. Treatment uses medicines that thin the blood to stop the clot growing while the body gradually dissolves it, a process that takes weeks to months, with the duration and choice set by the treating team.

Coughing up blood and lung cancer: what the evidence actually shows

This is the fear behind most searches for coughing up blood, so it deserves a direct answer. Lung cancer is a recognized cause of hemoptysis. It is also an uncommon one relative to infections and airway irritation. Both statements are true at the same time, and neither should be allowed to crowd out the other.

Tumors that grow in or near the airways have a fragile, abnormal blood supply and can erode into vessels, producing blood that may appear as streaks over weeks or, less often, in larger amounts. Guidance from the NHS and Mayo Clinic is consistent: the combination that raises concern is blood in sputum alongside age over roughly 40, a long smoking history, a new or changed cough that persists, unexplained weight loss, hoarseness, chest or shoulder pain, or repeated chest infections.

Absence of those features is genuinely reassuring but not a guarantee, which is why clinicians typically arrange a chest X-ray for anyone with unexplained hemoptysis and, when suspicion remains, a CT scan and possibly a camera examination of the airways (bronchoscopy).

Two facts are worth holding onto. The first is that a normal chest X-ray does not always exclude a small tumor, so persistent symptoms after a clear X-ray should still be followed up. The second is that the earlier a cancer is found, the wider the range of options, which is the strongest argument for getting a red streak checked rather than waiting to see whether it comes back.

Tuberculosis and other infections still worth ruling out

In much of the world, tuberculosis remains the first thing a clinician thinks of when a patient describes coughing up blood. The World Health Organization reports that roughly 10 million people fall ill with TB each year, and that about a quarter of the global population is estimated to have been infected with the bacterium at some point, most without ever developing disease.

Active TB in the lungs produces a cough that lasts for weeks, often with sputum and sometimes blood, alongside night sweats, fever, fatigue and weight loss. The bleeding comes from cavities and inflamed tissue that the infection carves into the lung. In countries where TB is uncommon, the diagnosis is easy to overlook, so clinicians pay attention to travel, time spent living or working in crowded settings, contact with someone who has TB, and any condition or treatment that weakens the immune system.

TB is not the only infection on the list. Fungal infections can colonize old lung cavities or affect people with weakened immunity, and certain parasitic infections acquired abroad can involve the lung. Lung abscesses, a collection of pus within the lung tissue, produce foul-smelling sputum that may be blood-streaked.

The practical message is simple. If a cough has lasted more than three weeks, especially with sweats or weight loss, mention it explicitly, and mention any travel or exposure history even if it seems irrelevant. TB is treatable with a prolonged course of medicines that must be taken exactly as prescribed, and confirming or excluding it early protects both the patient and the people around them.

Blood thinners, nosebleeds and other less obvious causes

Some causes hide in plain sight. Medicines that reduce the blood’s ability to clot, prescribed after a clot, for certain heart rhythm problems or after valve surgery, do not usually cause bleeding from a healthy airway. What they do is unmask bleeding that a normal clotting system would have stopped silently. A small vessel torn by a cough, which would otherwise have sealed within seconds, keeps weeping. Anyone on such treatment who notices blood in phlegm should tell their prescriber promptly, and should not stop or change the medicine on their own; the balance of risks belongs with the clinician who knows the reason it was started.

Nosebleeds, particularly during sleep, are a common source of morning blood that is spat out and assumed to be from the chest. Dry indoor air, nasal sprays and frequent nose-blowing all contribute. Gum disease and dental work can do the same on a smaller scale.

Rarer culprits include heart conditions that raise pressure in the lung circulation, such as a narrowed mitral valve or heart failure, which can push fluid and blood into the airways, often with frothy pink sputum and breathlessness lying flat. Inflammatory conditions that attack blood vessels can involve the lungs and kidneys together. Inhaled cocaine damages the airway lining directly. Blunt chest injury can bruise the lung. Cystic fibrosis, a genetic condition, causes bronchiectasis from childhood.

None of these is common, and none should be self-diagnosed from a list. They are the reason a clinician asks about medicines, drug use, heart history and joint or kidney symptoms when the chest story alone does not add up.

Why is coughing up blood in the morning so common?

Many people notice blood only in the first cough of the day and nowhere else, and the timing itself is a clue. Overnight, secretions that would normally be cleared by swallowing and small coughs pool in the airways and at the back of the throat. The first deep cough on waking moves several hours’ worth of mucus at once, and anything that has seeped into it, from inflamed bronchi or from a nose that bled quietly during the night, arrives in a single, alarming sample.

Dry bedroom air makes nasal membranes crack, and lying flat lets nasal blood drain backward rather than out of the nostrils. A person wakes, hawks, and sees red without ever suspecting the nose. Checking for crusting inside the nostrils, and noticing whether the blood is accompanied by phlegm and a chesty cough or by nasal stuffiness, often settles the question.

Morning-only blood is also typical of the chronic airway conditions discussed earlier. Bronchiectasis and chronic bronchitis both produce a productive morning cough, and blood streaks are most visible in that first clearance. Acid reflux at night can irritate the throat and larynx, producing a raw, hoarse morning and occasionally minor bleeding from the throat itself.

The reassuring pattern is small volume, mixed with mucus, clearing after the first cough and absent for the rest of the day. The pattern that should not be waited out is blood that persists through the day, increases in amount, or arrives with any of the warning signs covered next. Morning timing lowers suspicion a little; it does not remove the need for a review.

Should I go to the ER if coughing up blood?

The single most useful figure to remember comes from both the NHS and Mayo Clinic: call emergency services or get to an emergency department if you cough up more than a few teaspoons of blood, or if any amount of blood is accompanied by chest pain, severe breathlessness, dizziness or light-headedness. Larger amounts of blood in the airways can interfere with breathing itself, which is why volume is the deciding factor rather than how frightening the color looks.

When to seek care: Treat it as an emergency if you are coughing up more than a few teaspoons of blood, if the blood keeps coming and does not settle, if you feel faint, if breathing is difficult or painful, if your heart is racing, if you have a swollen painful leg, or if you have recently had surgery, a long journey or a chest injury. Anyone with a known heart or lung condition, or on medicines that thin the blood, should also err toward urgent assessment.

Outside those situations, blood in phlegm still warrants a same-day or next-day appointment with a doctor, not a note in the diary to mention at a check-up months away. That applies even to a single episode, and especially to anyone over 40, anyone who smokes or has smoked, and anyone with weight loss, night sweats or a cough that has outlasted three weeks.

What not to do: do not assume the first explanation that comes to mind, whether that is “just a cold” or “definitely cancer”. Do not stop prescribed medicines. Do not lie flat if bleeding is active; sitting up, and leaning toward the side of the chest that feels affected if one does, is generally advised while waiting for help. Bring the tissue or a photo; clinicians find it genuinely useful.

What happens at the doctor: questions, examination and tests

Expect the appointment to start with detective work rather than a scan. The clinician will want to know how much blood, how often, for how long, whether it was mixed with phlegm, and what the phlegm otherwise looks like. They will ask about fever, breathlessness, chest pain, weight, appetite, night sweats, smoking, medicines, travel, past lung problems and any recent surgery or immobility. Each answer moves items up or down the list of causes.

Examination follows: listening to the chest for crackles or wheeze that suggest infection or fluid, checking the nose and throat for an alternative source, looking at the legs for swelling, and checking pulse, breathing rate and oxygen levels.

Tests are chosen to fit the story. MedlinePlus lists the usual candidates: a chest X-ray as the first imaging step; blood tests for infection, anemia and clotting; a sputum sample sent to the laboratory for bacteria, including TB, and sometimes for abnormal cells; a CT scan of the chest when the X-ray is unclear or suspicion remains; and bronchoscopy, in which a thin flexible camera is passed into the airways to look directly and take samples. If a clot is suspected, a specialized CT of the lung arteries or a lung scan is used.

Not everyone needs all of these. A young non-smoker with a clear chest infection and a single streak of blood may need nothing more than a chest X-ray and a follow-up. Someone older with persistent bleeding will be worked through the list systematically. Ask what each test is looking for; a good clinician will tell you, and the answer usually reduces the fear rather than adding to it.

Coughing up blood but tests are normal: now what?

A surprising number of people go through the full sequence of X-ray, CT and even bronchoscopy and come out with no clear answer. Clinicians call this cryptogenic hemoptysis, a phrase that sounds ominous and mostly means “we looked hard and found nothing worrying”. It tends to occur in people whose bleeding was small, self-limiting and probably from airway inflammation that had healed by the time anyone looked.

What the evidence supports in this situation is neither dismissal nor endless testing but structured follow-up. Most such cases settle without further trouble. A minority declare themselves later, which is why doctors usually suggest a review if the bleeding recurs, changes in character or is joined by new symptoms, and why smokers in particular are often advised to have repeat imaging after an interval set by their clinician.

The frustrating middle ground, occasional streaks over months with normal tests, is real and deserves a plan rather than a shrug. Reasonable steps include keeping a simple log of dates and amounts, noting triggers such as infections or hard coughing bouts, checking whether the nose or throat could be the source, reviewing any blood-thinning medicines with the prescriber, and stopping smoking, which both reduces airway irritation and lowers the odds of the serious causes.

Here is the opinion this article has been building toward. The thing that matters most is not memorizing every cause but refusing two temptations: the temptation to ignore a red streak because it was small, and the temptation to assume the worst because the internet said so. Get it looked at, answer the questions honestly, follow up if it returns. That combination catches the serious causes early and spares the majority, whose bleeding was never dangerous, months of unnecessary dread.

Frequently asked questions

What are the common causes of coughing up blood?

The most frequent causes are a prolonged cough, acute bronchitis or a chest infection, pneumonia, bronchiectasis and flare-ups of COPD, all of which inflame and bruise the airway lining. Less common but more serious causes include a blood clot in the lung, tuberculosis, other lung infections and lung cancer. Medicines that thin the blood can make minor airway bleeding more visible, and blood from the nose or throat is often mistaken for blood from the lungs.

Can coughing up blood be nothing serious?

Often, yes. In young, otherwise healthy people a small streak of blood in phlegm during a chesty cold or chest infection is usually caused by irritated airways and settles as the cough does. The concern rises with age, a smoking history, larger amounts of blood, or added symptoms such as weight loss, night sweats, breathlessness or a cough lasting more than three weeks. Because the harmless and serious causes look alike at first, every episode should still be checked by a clinician.

Should I go to the ER if coughing up blood?

Go to an emergency department or call emergency services if you cough up more than a few teaspoons of blood, if the bleeding will not stop, or if any amount comes with chest pain, severe breathlessness, dizziness, a racing heart or a swollen painful leg. Smaller amounts without those features still need a doctor’s appointment within a day or so, particularly if you are over 40, smoke, take blood-thinning medicines or have a known heart or lung condition.

How do you know if blood is from your throat or lungs?

Blood from the lungs is typically bright red, often frothy, mixed with phlegm and produced by a cough. Blood from the nose or throat is usually spat rather than coughed, may follow nose-blowing or a night in dry air, and can be traced to crusting or a raw patch you can see in a mirror. Vomited blood from the stomach is darker, coffee-ground in texture and arrives with nausea. Describe exactly what you saw to your clinician rather than guessing.

What is hemoptysis and is it the same as coughing up blood?

Hemoptysis (spelled haemoptysis in British English) is simply the medical term for coughing up blood that originates in the lungs or airways. It covers everything from faint pink streaks in sputum to frank red blood. The term excludes blood that comes from the nose, throat or stomach, which is why the first step in assessing hemoptysis is confirming that the blood really did come from the chest.

Why do I cough up blood only in the morning?

Secretions pool in the airways and the back of the throat overnight, so the first deep cough of the day brings up several hours’ worth of mucus at once, along with any blood that seeped into it from inflamed bronchi or a nose that bled quietly during sleep. Dry bedroom air and lying flat both favor nasal bleeding that drains backward. Small morning-only streaks that clear quickly are less concerning than blood that persists through the day, but they still deserve a review.

Does blood in phlegm mean lung cancer?

Usually not. Lung cancer is a recognized cause of blood in phlegm but an uncommon one compared with infections and airway irritation. Suspicion rises when blood appears alongside age over about 40, a long smoking history, a new or changed cough that persists, unexplained weight loss, hoarseness or chest pain. Anyone with unexplained hemoptysis is normally offered a chest X-ray, and further scans if concern remains, so the way to settle the question is to be assessed rather than to wait.

Can a chest infection cause blood-streaked mucus?

Yes, and it is one of the most common explanations. Infection swells the airway lining and fills it with fragile new blood vessels, and repeated hard coughing tears them, leaving red streaks in yellow or green sputum. The blood is usually small in volume and fades as the cough eases. Rust-colored sputum with fever and breathlessness may indicate pneumonia, and blood that persists after the infection has cleared, or a cough lasting beyond three weeks, should be reassessed.

Can a blood clot in the lung cause coughing up blood?

It can. A pulmonary embolism blocks blood flow to part of the lung, and the affected tissue may bleed into the airways. The clue is the company the blood keeps: sudden breathlessness, sharp chest pain on breathing in, a fast heartbeat, light-headedness and sometimes a swollen, painful calf. Recent surgery, immobility, long journeys, pregnancy, cancer and a history of clots raise the risk. This combination needs emergency assessment rather than a routine appointment.

I take blood thinners and noticed blood in my phlegm. Should I stop them?

No, not without speaking to the clinician who prescribed them. Blood-thinning medicines rarely cause bleeding from healthy airways; they make minor bleeding from an irritated airway more visible and slower to stop. The underlying source still needs finding, and the reason the medicine was started, often a clot or a heart rhythm problem, carries its own risks if treatment is interrupted. Contact your prescriber promptly, and seek emergency care if the amount is more than a few teaspoons or you feel unwell.

References

• NHS – Coughing up blood (blood in phlegm)
• MedlinePlus – Coughing up blood
• NHS – Bronchiectasis
• World Health Organization – Tuberculosis fact sheet

This article is for general information only and is not a substitute for professional medical advice. Please consult a qualified doctor about your individual situation.