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Coughing up blood


There are various causes of coughing up blood (haemoptysis). If you cough up a lot of blood then call for an ambulance immediately. If you cough up smaller amounts of blood then see your doctor as soon as possible if you do not know the cause. This is because sometimes a serious condition such as cancer of the lung can be the cause. As a general rule, the earlier a serious problem is diagnosed, the better the chance that treatment may improve the outlook (prognosis). This leaflet discusses the main causes of coughing up blood.

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Why am I coughing up blood?

The medical word for coughing up blood is haemoptysis. This symptom is usually due to a problem within the airways or lungs. There is a range of different causes - discussed below.

The amount of blood can vary:

If you cough up a lot of blood

This is an emergency - especially if the bleeding does not stop and you are losing a lot of blood. You should call an ambulance urgently. However, this situation is very uncommon.

If you cough up a small amount of blood

Often the blood is mixed in with spit (sputum). This is the most common occurrence. Sometimes there is a small amount of blood mixed with sputum each time you cough. Sometimes it is a one-off small amount of blood. However, if you ever cough up blood and do not know the reason for it, no matter how small the amount of blood, you should see your doctor soon. Coughing up blood is a symptom which may indicate a serious disease. As a general rule, the earlier a serious problem is diagnosed, the better the chance that treatment may improve the outlook (prognosis).

Other symptoms may occur at the same time as coughing up blood. For example, cough, chest pain, breathlessness, a high temperature (fever), feeling unwell, wheeze or other lung symptoms. The presence and type of other symptoms may help to point to a cause of the bleeding. Sometimes there are no other symptoms at first.

Understanding the airways and the lungs

The two lungs are found in the chest - one on the right side and one on the left side. They are separated by the heart, which lies in between them.

Air that we breathe enters the nose, flows through the throat (pharynx) and voice box (larynx) and enters the windpipe (trachea). The trachea eventually divides into two parts called bronchi. The right main bronchus (bronchus is the word for one of the bronchi) supplies the right lung; the left main bronchus supplies the left lung. These bronchi then go on to divide into smaller bronchi.

Eventually, the bronchi become known as bronchioles - the smallest air tubes in the lungs. This system of air tubes can be thought of as an upside down tree, with the trachea being the main trunk and the bronchi and bronchioles being the branches. The medical term for all the air tubes is the respiratory tract.

At the end of the smallest bronchioles are alveoli. Alveoli are tiny sacs that are lined by a very thin layer of cells. They also have an excellent blood supply. The tiny alveoli are the place where oxygen enters the blood and where carbon dioxide (CO2) leaves the blood.

Chest and lungs fully labelled

Chest and lungs fully labelled

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What are the causes of coughing up blood?

Coughing up blood (haemoptysis) has many possible causes. Below is a brief overview of the more common and important causes:


Infection of the airways (bronchi), called acute bronchitis, and infection of the lung tissue, called pneumonia, are perhaps the most common causes of mild bouts of coughing up blood. However, infection anywhere in the airways may potentially cause haemoptysis. Typically, the blood is mixed up with spit (sputum). Also, other symptoms related to the infection will normally be present such as high temperature (fever) and cough. Typically, the haemoptysis goes when the infection clears. Often no further tests are needed if the haemoptysis is clearly linked to the infection and then goes.

Tuberculosis (TB) infection of the lung used to be a very common cause of haemoptysis. However, TB is now uncommon in the UK.


Most lung cancers arise from cells which line the bronchi. One of the earliest symptoms of lung cancer can be coughing up blood or bloodstained sputum. This may even be the first symptom before any other symptoms develop. Most lung cancers develop in people over the age of 50, often occurring in smokers. However, sometimes unusual types of lung cancer can affect younger non-smoking people. Various other symptoms usually also develop. These symptoms are explained in the separate leaflet called Lung Cancer.


Bronchiectasis is an abnormal widening of one or more airways. Extra mucus is made in the abnormal airways, which is prone to infection. The main symptom is a cough which produces a lot of sputum. You may also cough up some blood from the abnormal inflamed airway. This is typically just small amounts of blood now and then. Occasionally, a large amount of blood can be coughed up. There are various underlying causes of bronchiectasis. For example, a previous severe lung infection, some inherited conditions and some other conditions that can damage part of an airway.

Objects breathed in (inhaled) and injury (trauma)

Inhaled objects can cause damage to an airway and lead to haemoptysis. For example, an inhaled peanut or small toy may sometimes be a cause in small children. Other types of injury to a lung or airway can cause haemoptysis.

A pulmonary embolism

A pulmonary embolism is a serious, potentially life-threatening condition. It is due to a blockage in a blood vessel in the lungs. The main symptoms are usually chest pain and breathlessness, but haemoptysis may also occur.

Heart and blood vessel problems

Severe heart failure can cause a build-up of fluid in the lungs. The main symptom is usually breathlessness but the sputum may become frothy and bloodstained. Various rare blood vessel problems may also cause bleeding into the lungs or airways.

Inflammation and abnormal tissue deposits

There are a number of conditions that can cause inflammation or produce abnormal tissue deposits in various parts of the body. Sometimes these conditions affect lung tissue or airways. Inflamed or abnormal tissue in the airways or lungs may bleed from time to time and cause haemoptysis. Conditions that can cause this include Goodpasture's syndrome, pulmonary haemosiderosis, granulomatosis with polyangiitis, lupus pneumonitis, pulmonary endometriosis, and broncholithiasis. Note: these conditions are very rare and you would normally have other symptoms in addition to the haemoptysis.

No cause identified

Despite tests, no cause can be found in around one in eight people with haemoptysis. This is called idiopathic haemoptysis. (The word idiopathic means of unknown cause.)

So, in some people the cause of the bleeding remains a mystery. Perhaps in these cases it is just a small blood vessel that bursts and bleeds for a while - a bit like a nosebleed. However, never assume that there will be no cause found. Always see a doctor if you cough up blood and the cause is not known. The diagnosis of idiopathic haemoptysis can only be made once other more serious causes can be ruled out.

What should I do if I cough up blood?

As mentioned earlier:

  • If you cough up lots of blood then you should call an ambulance, as this is a medical emergency.

  • If you cough up one or more small amounts of blood and you do not know the cause then see a doctor promptly.

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What assessment and tests may be done?

A doctor's assessment

Your doctor is likely to ask various questions about the nature of the bleeding, and ask if you have any other symptoms. They will also examine you. One of the first things a doctor will try to find out is: "Is this blood truly coming from the airways or lungs?" Sometimes it is difficult to be sure. True haemoptysis is the coughing up of blood that comes somewhere from the lung or airways below the level of the larynx. But sometimes it can be difficult to say if the blood is:

  • Haematemesis - that is, when the blood is brought up (vomited) blood but the vomiting may cause you to cough as you vomit.

  • Pseudohaemoptysis - that is, when the blood comes from somewhere in your mouth or nose and tracks to the back of your throat, which then causes you to cough. For example, from a nosebleed or an inflamed throat.

Following a doctor's assessment, the likely cause may be clear and your doctor will advise on what to do next. Tests may or may not be appropriate.

However, on clarifying that the blood is a true haemoptysis, and the cause is not clear, your doctor may refer you for one or more tests. The tests done can vary depending on the suspected cause (which is often based on your other symptoms). Tests that are commonly done following an unexplained haemoptysis include one or more of the following.

Chest X-ray

An ordinary X-ray is a quick and easy test. It may be all that is needed to diagnose or assess various problems. However, an ordinary X-ray has limited use. Other tests may be needed if the diagnosis is not clear on an ordinary X-ray picture.

CT Scan

A CT scan is a specialised X-ray test. It can give quite clear pictures of the inside of your body. In particular, it can give good pictures of soft tissues of the body which do not show well on ordinary X-ray pictures.


A bronchoscopy is a procedure which involves a healthcare professional looking into your large airways (the trachea and bronchi). A fibre-optic bronchoscope is the device usually used. This is a thin, flexible telescope. It is about as thick as a pencil. The bronchoscope is passed through the nose or mouth, down the back of the throat, into the windpipe (trachea), and down into the bronchi. The fibre optics allow light to shine around bends in the bronchoscope and so the clinician can see clearly inside your airways.

Blood tests

A range of blood tests can help to diagnose various conditions.

Other tests

Various more sophisticated tests and scans may be advised if the diagnosis or extent of the problem remains unclear despite the above tests.

Haemoptysis treatment

The treatment depends on the cause. See individual leaflets on the various diseases that can cause coughing up of blood.

Further reading and references

Article history

The information on this page is written and peer reviewed by qualified clinicians.

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