Coughing up blood (blood in phlegm)

Coughing up blood can be alarming, but isn't necessarily a sign of a serious problem. It's more likely to be a cause for concern the older you are, particularly if you smoke. You should see your GP as soon as possible if you cough up blood.

About coughing up blood 

In up to one in five cases investigated, no cause is found for coughing up blood.

If you are coughing up blood, you may cough up:

  • small amounts of bright red blood
  • frothy blood-streaked sputum – sputum is saliva (liquid produced in your mouth) and phlegm (a thick liquid produced, especially when a person has a cold)

The blood is usually from your lungs. It’s often the result of coughing for long periods or a chest infection.

Mostly, if you cough up blood, the bleeding will stop on its own. In about five per cent of people (who cough up blood for the first time) the bleeding will be severe.

This bleeding can be life threatening - call 999 if this is happening.

If the blood is dark and contains bits of food or what looks like coffee grounds, it may be coming from your digestive system.

This may also be a serious problem. You should go to hospital straight away if you vomit up blood.

What to do if you cough up blood 

See your GP as soon as possible if you cough up blood. It's particularly important to see your GP if:

Your GP will be able to assess whether you may have a serious medical condition that needs to be investigated and treated. Call GP out of hours service if you can't see your GP.

Call 999 for an ambulance or go to your nearest emergency department immediately if you're coughing up significant amounts of blood or are struggling to breathe.

Tests that may be needed 

You may be asked for a sample of your sputum so it can be checked for infection. Other tests, such as blood tests, may also be needed.

Your GP may decide to refer you to a specialist at your local hospital. Tests that may be carried out include a:

  • chest X-ray 
  • more detailed scan, such as a computerised tomography (CT) scan

In some cases, further tests may be required to find out where the blood is coming from. For example, you may have a test called a bronchoscopy. This is where the main air passages of your lungs are examined using a tube with a camera at one end.

Common causes of coughing up blood 

The information below can give you a better idea of what may be the reason for coughing up of blood.

Don't use it to diagnose yourself - always leave that to a doctor.

The most common reason for coughing up blood is a chest infection.

Where a specific cause is found, the most common causes include:

  • pneumonia - a swelling (inflammation) of the tissue in one or both of your lungs usually caused by an infection with a germ (bacterium or virus)
  • bronchitis  - an infection of the main airways of the lungs (bronchi), causing them to become irritated and inflamed (it can be caused by either a virus or bacteria, although viral bronchitis is much more common)
  • tuberculosis (TB) – a severe lung infection associated with fever and sweating which can be treated with antibiotics 

Sometimes a severe nosebleed or bleeding from the mouth or throat can cause blood to come out in your saliva when you cough.

Less common causes of coughing up blood 

Less commonly, coughing up blood may be the result of:

  • bronchiectasis – this is more likely if you're also wheezy or short of breath
  • pulmonary embolism (a blood clot in the lungs) – this usually causes sudden shortness of breath and chest pain
  • pulmonary oedema (fluid in the lungs) – your sputum will be pink and frothy, and this usually occurs in people with pre-existing heart problems
  • lung cancer – this is more likely if you're over 40 and smoke
  • cancer of the throat or windpipe
  • taking anticoagulants – medications that help stop your blood clotting, such as  warfarin or other oral anticoagulants

Sometimes, in 15 to 20 per cent of cases, no cause can be found and it never happens again.

The information on this page has been adapted from original content from the NHS website.

For further information see terms and conditions.

This page was reviewed February 2019

This page is due for review December 2021

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