Quick answer. Coughing up blood (haemoptysis) is most often caused by chest infections or bronchitis, but it can also signal tuberculosis, bronchiectasis, lung cancer or a pulmonary embolism. The single biggest red flag is coughing up a large volume of blood (more than a few teaspoons) or struggling to breathe — call 995 immediately.
Coughing up blood, known medically as haemoptysis, means bringing up blood or blood-stained phlegm from your lungs or airways. It can range from faint streaks in your mucus to larger, frightening amounts. In Singapore, the most common causes are relatively minor chest infections, but because tuberculosis (TB) remains present in our community and is a notifiable disease, any haemoptysis deserves prompt medical assessment.
It is important to work out where the blood is actually coming from. Blood from a nosebleed dripping down the throat, or blood that is vomited from the stomach (which is usually darker and mixed with food), is different from true haemoptysis. This guide explains the common causes, the warning signs that mean you should not wait, and which specialist in Singapore can help you get the right tests.
At a glance
| Possible cause | Typical features | How urgent |
|---|---|---|
| Chest infection / bronchitis | Cough with coloured phlegm, fever, blood streaks | See a GP within days |
| Tuberculosis (TB) | Weeks of cough, weight loss, night sweats, fatigue | Urgent — TB is notifiable in Singapore |
| Bronchiectasis | Long-standing daily phlegm, recurrent infections | See a doctor soon |
| Lung cancer | Persistent cough, weight loss, often a smoking history | Urgent assessment needed |
| Pulmonary embolism (PE) | Sudden breathlessness, chest pain, fast heartbeat | Emergency — call 995 |
Red flags: when to seek urgent care
Coughing up blood can occasionally signal a life-threatening problem. Call 995 or go to A&E immediately if you experience any of the following:
- Coughing up a large amount of blood (more than a few teaspoons) or blood that keeps coming.
- Severe breathlessness, chest pain, or a feeling that you cannot get enough air.
- Feeling faint, dizzy, pale, clammy or about to collapse.
- A fast heartbeat with sudden breathlessness, which can indicate a pulmonary embolism.
Even small amounts of blood should be assessed promptly by a doctor, especially if it happens more than once, you are a smoker, or you have had weeks of cough, weight loss or night sweats — these can be signs of TB or lung cancer.
Chest infections and bronchitis
The most common reason for coughing up small amounts of blood is a chest infection or acute bronchitis. Forceful coughing irritates and inflames the airways, which can cause small blood vessels to break and produce blood-streaked phlegm.
This is usually accompanied by a cough with coloured phlegm, fever and a general feeling of being unwell. It often settles as the infection clears, but you should see a doctor if the blood continues, the infection does not improve, or you feel increasingly breathless.
Tuberculosis (TB) — important in Singapore
Tuberculosis remains relevant in Singapore and is a notifiable disease, meaning confirmed cases must be reported to the Ministry of Health (MOH). TB is a bacterial infection that mainly affects the lungs and can cause coughing up blood.
Warning signs include a cough lasting more than two to three weeks, coughing up blood or phlegm, unexplained weight loss, fever, night sweats and persistent tiredness. If you have these symptoms, see a doctor promptly. TB is treatable with a course of antibiotics, and early diagnosis also protects the people around you.
Bronchiectasis and lung cancer
Bronchiectasis is a long-term condition in which the airways become widened and scarred, leading to a build-up of mucus, repeated chest infections and sometimes coughing up blood. People often have a daily cough with large amounts of phlegm over many years.
Lung cancer is a less common but serious cause. Suspicious features include a persistent or changing cough, coughing up blood, unexplained weight loss, chest pain and breathlessness, particularly in current or former smokers or those over 40. Any of these symptoms should be investigated without delay.
Is it really from the lungs? Nosebleeds and vomited blood
Before assuming blood is from your lungs, it helps to consider where it is coming from:
- Nosebleed (epistaxis): Blood from the back of the nose can drip into the throat and be coughed up, mimicking haemoptysis.
- Vomited blood (haematemesis): Blood from the stomach is usually darker, may look like coffee grounds, and is brought up with retching rather than coughing. This is a separate emergency.
- True haemoptysis: Blood from the lungs is usually bright red, frothy and mixed with mucus, and comes up with coughing.
If you are unsure, treat it seriously and get medical advice.
Which specialist should you see?
For coughing up blood, the most relevant specialist is a respiratory physician (lung specialist), who can arrange a chest X-ray, CT scan, sputum tests for TB and a bronchoscopy if needed. You can compare and find a doctor here: best respiratory physicians in Singapore.
If you are coughing up a large amount of blood or are very breathless, do not wait for an appointment — call 995 or go to the nearest A&E. For milder, one-off blood-streaked phlegm, start with your GP, who can refer you to a specialist if necessary.
What to expect at your appointment
When you see a doctor about coughing up blood, expect questions about how much blood there is, its colour, how long you have been coughing, and any weight loss, fever, night sweats or smoking history. The doctor will listen to your chest and usually arrange a chest X-ray and blood tests. If tuberculosis is possible, you may be asked to provide sputum samples; a CT scan or a bronchoscopy (a camera test of the airways) may follow depending on the results.
How to prepare and protect others
- Note the amount and colour of blood, ideally with a photo, and whether it is mixed with phlegm.
- List your symptoms, medical conditions, medicines and any recent travel or contact with someone who has TB.
- If you have a persistent cough with weight loss or night sweats, wear a mask and avoid close contact with others until you have been assessed, as a precaution.
Common questions
Is a small amount of blood in phlegm always serious?
Not always; small streaks often come from a chest infection or forceful coughing. However, because TB and other conditions can also cause this, any blood in phlegm should be assessed promptly, especially if it recurs or comes with weeks of cough, weight loss or night sweats.
How can I tell if blood is from my lungs or my stomach?
Blood from the lungs is usually bright red, frothy and mixed with mucus and comes up with coughing. Blood from the stomach is often darker, may look like coffee grounds, and comes up with retching. If you are unsure, treat it seriously and seek medical advice.
Related guides
- Best Respiratory & Lung Clinics in Singapore — our editorial shortlist
- Vomiting blood
- Wheezing
- Double vision
Sources
- NHS — Coughing up blood (blood in phlegm)
- HealthHub Singapore — Tuberculosis
- MOH Singapore — Communicable Diseases (Notifiable)
- Mayo Clinic — Coughing up blood
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