Pneumonia is swelling (inflammation) of the tissue in one or both of your lungs. It's usually caused by an infection.

At the end of the breathing tubes in your lungs are clusters of tiny air sacs. If you have pneumonia, these tiny sacs become inflamed and swell up with fluid.

Terms such as bronchopneumonia, lobar pneumonia and double pneumonia are sometimes used, but refer to the same condition with the same causes and treatment.

Common symptoms of pneumonia include:

a cough – which may produce thick mucus (phlegm) that is yellow, green, brownish or blood-stained
difficulty breathing

When to see your GP

If you feel very unwell and experience any of the symptoms of pneumonia, see your GP.

You may need a chest X-ray or further tests to confirm the diagnosis.

If you are experiencing severe symptoms – such as rapid breathing, chest pain or confusion – seek urgent medical attention.

What causes pneumonia?

The most common cause of pneumonia is a pneumococcal infection, caused by bacteria called Streptococcus pneumoniae.

However, there are many different types of bacteria and viruses that can lead to pneumonia.

Good hygiene and a healthy lifestyle can help prevent pneumonia. Try to avoid smoking, as it damages your lungs and increases the chance of infection.

People at high risk of pneumonia should also be offered the pneumo jab and the flu jab.

How is pneumonia treated?

Mild cases of pneumonia can usually be treated at home withantibiotics, rest and fluids. People who are otherwise healthy will normally recover well.

For people with other health conditions, pneumonia can sometimes be severe and may need to be treated in hospital.

This is because pneumonia can lead to complications, some of which can be fatal, depending on the health and age of the patient. These include:

respiratory failure (when the lungs cannot take in enough oxygen) due to the air sacs filling with fluid
lung abscesses
blood poisoning (septicaemia)

Who is affected?

In the UK, pneumonia affects around 1 in 1000 adults each year. It is more common during autumn and winter.

Pneumonia can affect people of any age, although it is more common and can be more serious in groups such as:

babies, young children and elderly people
people who smoke
people with other health conditions, such as a lung condition or a weakened immune system

People in these groups are more likely to need hospital treatment.

Symptoms of pneumonia

The symptoms of pneumonia can develop suddenly (over 24-48 hours) or may come on more slowly, over several days.

Pneumonia symptoms vary and can be similar to those of other chest infections, such as acute bronchitis.

Common symptoms of pneumonia

You are likely to have a cough. This can be dry, or may produce thick mucus (phlegm) that is yellow, green, brownish or blood-stained.

Other common symptoms include:

difficulty breathing – your breathing may be rapid and shallow, and you may feel breathless, even when resting
rapid heartbeat
feeling generally unwell
sweating and shivering
loss of appetite
pain in your chest – which gets worse when breathing or coughing

Less common symptoms

Less commonly, symptoms of pneumonia can include:

coughing up blood (haemoptysis)
nausea or vomiting
pain in your joints and muscles
feeling confused and disorientated, particularly in elderly people

When to see your GP

If you experience any symptoms of pneumonia, see your GP.

If you are experiencing severe symptoms – particularly rapid breathing, pain or confusion – seek urgent medical attention.

Causes of pneumonia

Pneumonia is most commonly caused by an infection, usually bacterial.

However, many different bacteria, viruses and – more rarely – fungi cause pneumonia.

The germs that cause an infection are usually breathed in. In rare cases, pneumonia can develop from an infection elsewhere in your body, when germs enter your lungs through your bloodstream.

The four types of pneumonia are described in more detail below.

Bacterial pneumonia

The most common cause of pneumonia in adults is a bacterium called Streptococcus pneumoniae. This form of pneumonia is sometimes called pneumococcal pneumonia.

Less commonly, other types of bacteria can cause pneumonia, including:

Haemophilus influenzae
Staphylococcus aureus
Mycoplasma pneumoniae – outbreaks tend to occur every four to seven years, more commonly in children and young people

The following are rare causes of bacterial pneumonia:

Chlamydophila psittaci – this causes a rare form of pneumonia called psittacosis, which can be passed on to people from infected birds such as parrots, parakeets, pigeons, canaries and budgies; this condition is also called parrot fever or parrot disease
Chlamydophila pneumoniae
Legionella pneumophila – this causes Legionnaires' disease, an uncommon form of pneumonia

Viral pneumonia

Viruses can also cause pneumonia, most commonly the respiratory syncytial virus (RSV), and sometimes the flu (influenza) type A or B virus.

Viruses are a common cause of pneumonia in young children.

Aspiration pneumonia

Rarely, pneumonia can be caused by breathing in:

a foreign object, such as a peanut
a harmful substance, such as smoke or a chemical

The object or substance inhaled causes irritation in the lungs or damages them. This is called aspiration pneumonia.

Fungal pneumonia

In the UK, pneumonia caused by fungal infection of the lungs is rare in people who are normally healthy. It more often affects people whose immune systems are weakened (see below).

While still rare, fungal pneumonia is more likely to affect people who travel to places where these infections are more commonly found, such as parts of the US, Mexico, South America and Africa.

The medical names for fungal pneumonia include histoplasmosis, coccidioidomycosis and blastomycosis.

People at risk

The following people have a higher risk of developing pneumonia:

babies and very young children
elderly people
people who smoke
people with other health conditions
people with a weakened immune system

Health conditions that increase the risk of pneumonia developing include:

another lung condition, such as asthma or cystic fibrosis
a heart condition
a kidney or liver condition
a lowered immune system

Your immune system can be weakened because of:

a recent illness, such as flu
treatment for cancer, such as chemotherapy
medicines that weaken the immune system after an organ transplant

Hospital-acquired pneumonia

People in hospital for another condition, or a procedure such as an operation, can develop pneumonia caused by germs acquired from the hospital. This is called hospital-acquired pneumonia.

People on breathing machines in the intensive care unit are at particular risk; this is known as ventilator-associated pneumonia. The pattern of germs is different to other types of pneumonia, and they are sometimes resistant to antibiotics. However, these types of pneumonia can still be treated with antibiotics.

Diagnosing pneumonia

Your GP can often diagnose pneumonia by asking questions about your symptoms and examining your chest. In some cases, further tests may be needed.

Pneumonia can sometimes be difficult to diagnose, as it shares many symptoms with other conditions, such as the common cold, bronchitis and asthma.

To make a diagnosis, your doctor may first ask:

if you are breathing faster than usual
if you feel breathless
how long you have had your cough
whether you are coughing up sputum and what colour it is
if the pain in your chest is worse when you breathe in or out

Your doctor will probably take your temperature and listen to the back and front of your chest with a stethoscope, to check for any crackling or rattling sounds.

They may also listen to your chest by tapping it. Lungs filled with fluid produce a different sound to normal, healthy lungs.

Most people with mild pneumonia do not need to have a chest X-ray or any other tests.

Chest X-ray and other tests

Your GP may arrange a chest X-ray or other tests if your symptoms have not started to improve within 48 hours of starting treatment.

A chest X-ray can show how much your lungs are affected. It can also help the doctor distinguish between pneumonia and other chest infections, such as bronchitis.

Your GP may also arrange:

a sputum test
blood tests

Analysing samples of sputum or blood can help identify the bacterium or virus causing the infection.

Screening for lung cancer

Although uncommon, pneumonia can sometimes be a symptom of underlying lung cancer in people who smoke and are 50 years of age or over.

If you fall into one of these groups, your GP may refer you for a chest X-ray.

If your X-ray does not detect cancer, a follow-up X-ray is recommended six weeks later. This is a way of "double-checking" that all is well with your lungs.

Treating pneumonia

Mild cases of pneumonia can usually be treated at home with antibiotics and plenty of rest and fluids. More severe cases may need hospital treatment.

Treatment at home

You may continue to cough for two to three weeks after finishing your course of antibiotics, and feel tired for even longer, as your body continues to recover.

Tell your GP if your symptoms don't get better within two days of starting treatment. Your symptoms may not have improved because:

the bacteria causing the infection may be resistant to antibiotics –your doctor may change to a different antibiotic, or may start treating you with a second antibiotic while you continue to take the first one
a virus may be causing the infection, rather than bacteria– antibiotics have no effect on viruses, and your body's immune system will have to fight the viral infection by creating antibodies

Treatment in hospital

You may need hospital treatment if your symptoms are severe. This includes antibiotics and fluids given intravenously through a drip, or oxygen to help breathing.

In very serious cases of pneumonia, breathing may need to be assisted through a ventilator in an intensive care unit (ICU).


The steps below may help ease your symptoms.

You can take painkillers such as paracetamol or ibuprofen to relieve pain and reduce fever. However, you should not take ibuprofen if you:

are allergic to aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs)
have asthma, kidney disease, a history of stomach ulcers or indigestion

Cough medicines are not recommended. Coughing lets you clear mucus from your lungs, so trying to stop your cough could make the infection last longer.

Also, there is little evidence that cough medicines are effective. A warm drink of honey and lemon can help relieve the discomfort caused by coughing.

Drink plenty of fluids to avoid dehydration, and get plenty of rest to help your body recover.

If you smoke, it's more important than ever to stop, as smoking damages your lungs. Read information and tips on how to stop smoking.

Pneumonia is not usually passed from one person to another, so it is safe to be around others, including family members. However, it is sensible for those with weakened immune systems to avoid a person with pneumonia until they start to get better.

Once your symptoms improve, it may take a while for you to fully recover, and your coughing may continue for some time. Speak to your GP if you are concerned.

After treatment

Your GP will probably ask to see you again around six weeks after you start your antibiotics.

In some cases, they may arrange follow-up tests, such as a chest X-ray, if:

your symptoms have not improved
your symptoms have come back
you smoke
you are over the age of 50

Some people may be advised to have vaccinations against flu or pneumococcal infections after recovering from pneumonia.

Aspiration pneumonia

If you have breathed in an object that is causing your pneumonia, it may need to be removed.

The doctor may do this by using a tube to look into the airways in your lungs, and then removing the inhaled object. This is called a bronchoscopy.

Complications of pneumonia

Complications of pneumonia are more common in older people, young children and people with existing health conditions, such as diabetes.

If you develop complications, you will be admitted to hospital for treatment.

The most common complications of pneumonia are pleurisy, a lung abscess and blood poisoning (septicaemia), described below.


Pneumonia can cause pleurisy, which is inflammation of the pleura – the two thin linings between your lungs and your ribcage.

Less commonly, fluid can build up in the space between your lungs and the wall of your chest. This is called a pleural effusion.

Pleural effusion affects around half of people admitted to hospital with pneumonia.

The fluid can put pressure on the lungs, making it difficult to breathe. Pleural effusion usually gets better by itself when pneumonia is treated.

In around 1 in 10 cases of pneumonia treated in hospital, the fluids that make up a pleural effusion become infected by bacteria, which causes a build-up of pus. This is known as empyema.

The infected fluid is usually drained using a needle or a thin tube. The most serious cases may need surgery to remove the pus and repair any damage to the pleura and lungs.

Lung abscess

A lung abscess is a rare complication of pneumonia and mostly seen in people who have a serious, pre-existing illness, or those with a history of severe alcohol misuse.

A lung abscess is a pus-filled cavity that develops inside the tissue of the lungs. Coughing up unpleasant-smelling phlegm and swelling in your fingers and toes are signs of a lung abscess.

Lung abscesses can often be treated using antibiotics. This usually involves an initial course of intravenous antibiotics, followed by antibiotic tablets for four to six weeks.

Most people start to feel better within three to four days. It's important to finish your recommended course of antibiotics, even if you feel perfectly healthy, to prevent re-infection of your lungs.

Around 1 in 10 people with a lung abscess need surgery to drain the pus out of the abscess or remove the affected section of the lung.

Blood poisoning

Another rare and serious complication of pneumonia is blood poisoning, also known as septicaemia.

Symptoms of septicaemia include:

high temperature (fever) of 38ºC (100.4ºF) or above
fast heartbeat and breathing
low blood pressure (hypotension), which will cause you to feel dizzy when you stand up
a change in mental behaviour, such as confusion or disorientation
reduced urine flow
cold, clammy and pale skin
loss of consciousness

Once your blood has become infected, it's possible for the infection to spread to other organs in your body, such as:

the outer layers of your brain (meningitis)
the lining of your abdomen (peritonitis)
the inner layer of your heart (endocarditis)
your joints (septic arthritis)

These types of infections are called metastatic infections and are usually serious, requiring treatment with high-dose intravenous antibiotics.

Preventing pneumonia

You can help prevent pneumonia by practising good hygiene to stop germs spreading.

For example:

when you cough or sneeze, cover your mouth and nose with a tissue to catch the germs
throw used tissues away immediately, in a bin or toilet – germs can live for several hours after they leave your nose or mouth
wash your hands regularly, to avoid transferring germs to other people or objects


To help protect against pneumonia, people in higher risk groups should be vaccinated. The recommended vaccinations are:

the pneumonia jab (pneumococcal vaccination), which protects against pneumococcal infections
the flu jab


Smoking, alcohol misuse and intravenous drug abuse can increase your risk of developing pneumonia.


Smoking damages your lungs, which means they become infected more easily.

If you smoke, the best thing you can do to prevent pneumonia is to quit smoking.

To help you quit, the Smoking Helpline (0300 123 1044) offers advice and support. For more information, visit the Smokefree website.

Your GP or pharmacist can also give help and advice on how to quit smoking.

Alcohol misuse

Excessive and prolonged alcohol misuse is known to weaken your lungs' natural defences against infections, making you more vulnerable to pneumonia.

One study found that 45% of people admitted to hospital with pneumonia had an alcohol problem. Alcohol misuse is defined as regularly drinking over the recommended weekly limits (21 units of alcohol for men and 14 units for women).

Not only does alcohol misuse increase your risk of developing pneumonia, it also increases your risk of it being more serious. It is estimated that people who misuse alcohol are three to seven times more likely to die from pneumonia than the general population.

If you drink alcohol, do not exceed recommended daily limits (three to four units a day for men and two to three units a day for women).

Talk to your GP if you are finding it difficult to moderate your drinking. Counselling services and medication are available to help you reduce your alcohol intake.