Phlegm and mucus

Find out what phlegm is, what causes it, what changes to your phlegm could mean, and how to treat and manage it. 

What are mucus and phlegm?

Mucus is a jelly-like liquid that is found all over the body to keep you healthy and protect you from infection.

Phlegm is the specific name for the mucus that you cough up from your lungs. Your healthcare professional might call it ‘sputum’. Phlegm protects your airways and lungs. 

Most of the time, coughing up a little bit of phlegm is normal and healthy. But if your phlegm changes in colour, thickness, or amount this could be a sign you’re unwell.

What causes phlegm?

Coughing up phlegm doesn’t always mean you have a lung condition. There are other common causes including:

  • colds
  • viruses
  • infections
  • allergies
  • air pollution
  • catarrh – a build-up of mucus in your nose and sinuses 
  • smoking. 

But some people with lung conditions, like asthma, chronic obstructive pulmonary disease (COPD), bronchiectasis, cystic fibrosis, or lung cancer find they produce more phlegm.

Does phlegm mean my lung condition is getting worse?

Coughing up more phlegm than usual could be a sign of inflammation in your airways or a flare-up of your lung condition. 

Make sure you keep taking all your medicines as prescribed and follow your self-management plan. If you continue to cough up more phlegm than usual, book an appointment with your GP or nurse. They might test a sample of your phlegm to find out more.

What does your phlegm mean?

Asthma + Lung UK nurse, Claire, explains what your phlegm means and what to look out for in terms of colour, thickness or amount.

What does the colour of your phlegm mean?

The colour of your phlegm can change when you’re ill. Everyone’s phlegm looks different. But here is a general guide to what different colours of phlegm may mean: 

White or clear phlegm 

A bit of white or clear phlegm now and then is completely normal. However, if you’re producing a lot of white or clear phlegm, it could be a sign of inflammation in your airways or a flare-up of your lung condition. Clear phlegm is also a sign of hay fever or other allergies. 

If you have a lung condition, the best way to manage white or clear phlegm is to take your usual medicines as prescribed, including taking antihistamines if your allergies are flaring up. But if it’s not improving, speak to your GP or nurse. 

Yellow or green phlegm 

Yellow or green phlegm might be a sign of an infection, like a cold, the flu or a chest infection. 

Infections often make your lung condition symptoms worse. This is why it’s important to keep taking your lung condition medicines every day as prescribed to control your symptoms. 

If you’re not getting better talk to your GP or nurse to see if you need antibiotics or steroids to treat the infection. They will ask about other symptoms as well as the colour of your phlegm to try to understand what the cause might be.  

Find out how to reduce your risk of catching a cold or the flu if you have a lung condition.


Not all infections need antibiotics. Antibiotics only work for bacterial infections, like pneumonia. They will not help with viral infections, like flu.

Phlegm streaked with blood 

If you cough up blood, call your GP surgery or 111 as soon as possible. Even if it's just a tiny bit of blood it’s important to get it checked. 

Coughing up blood can be alarming, but it doesn’t necessarily mean there’s a serious problem.  If you cough up blood, it is usually because you have been coughing a lot or you have a chest infection. The NHS has more information on the common causes of coughing up blood as well as some less common ones.

Call 999 or go to A&E for urgent help

•    if you’re coughing up more than just a few streaks of blood
•    if you’re coughing up blood, finding it hard to breathe, have a very fast heartbeat, or pain in your chest or upper back.

Brown or black phlegm 

There are a few reasons why you may get brown or black phlegm. 

One of the most common causes is smoking. If you smoke and have a lung condition, quitting is one of the best things you can do for your health. We have information to help you quit.

Other causes of brown or black phlegm include exposure to dust or dirt such as coal, pneumonia, bronchiectasis, chronic obstructive pulmonary disease (COPD), tuberculosis (TB), lung cancer, cystic fibrosis, and fungal infections. 
If you’re coughing up brown or black phlegm, contact your GP. 

Treating and managing phlegm

If you have a lung condition

Make sure you take all your usual medicines as prescribed to help you manage and treat your symptoms. If you’re still coughing up more phlegm than usual, book an appointment with your GP or nurse.

In most healthy people, coughing up more phlegm than normal will go away on its own. But if you’ve been coughing up phlegm for more than three weeks, make an appointment with your GP. 

If you have a lung condition, it’s important to understand how to prevent, treat and manage excess phlegm as this will help you manage your lung condition well. Talk to your GP, nurse, or pharmacist to find out what will work best for you.

Medicines for phlegm

Medicines to treat phlegm depend on the underlying cause and may include:

If you have COPD or bronchiectasis, you may have a rescue pack of antibiotics and steroids at home to take if you have a chest infection. Follow the instructions on your self-management plan about when to take them. Speak to your healthcare professional if you’re not sure. 

There is little evidence to show cough medicines help with phlegm. But some people find it helps them to cough less. A hot lemon and honey drink has a similar effect. 

Clearing phlegm from your lungs

If you have a lung condition, it is important to clear phlegm from your chest as it can damage the lining of the lungs and increase your risk of a chest infection. 

Ask to see a physiotherapist who can teach you some breathing exercises called airway clearance techniques (ACTs) to help you clear phlegm from your lungs.

Airway clearance devices

A physiotherapist may suggest you use a small handheld airway clearance device to help you clear phlegm from your lungs. Examples include the Acapella and the Flutter.

Only use an airway clearance device if your physiotherapist has recommended one for you. They will help you select the best device for you and show you how to use it correctly.

Other ways to manage phlegm  

  • Drink plenty of water. This will help to keep your phlegm loose. Try to drink 6-8 glasses of water a day. Taking frequent sips of water can help you to cough less. 
  • Stop smoking (if you smoke). This can improve your phlegm and lung health in general. We have information to help you quit.
  • Inhale steam. Try sitting in a bathroom with a hot shower running for a while. This can help loosen phlegm in your lungs so you can cough it up more easily.
  • Keep active. Staying active can help to clear the phlegm from your lungs. Why not try our Keep Active videos.

Get support

Call or WhatsApp our Helpline for support with your condition. Get advice on your medicines, symptoms or travelling with a lung condition, or just call us to say hello.

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