What is breathlessness and why might you get it?

If you’re breathless, you may experience uncomfortable or fast breathing. You may feel short of breath or your chest may feel tight. There are several things that can cause breathlessness. These include:

  • cancer affecting the lungs
  • a build-up of fluid in the lungs or stomach
  • low levels of red blood cells
  • chest infections
  • weak muscles
  • pain
  • blood clots
  • smoking
  • anxiety
  • cancer treatments.

Your doctor can explain the cause of your breathlessness and help you find the most appropriate treatment. Your doctor may suggest you use a Borg scale to show how breathless you feel at different times. A Borg scale uses numbers 0 to 10, with 10 being severe breathlessness. You can use this to keep a diary of your breathlessness. This may help you know what makes it worse so you can manage your activities.

If you feel down, depressed or isolated because of your breathlessness, speak to your GP about medicines or counseling that may help you.

The lungs

To make it easier to understand breathlessness, it may help to understand the way lungs work.

We have two lungs – one on each side of the chest. When we breathe in, air passes from our nose or mouth through the windpipe (trachea), which divides into two tubes (airways), one going to each lung. These are known as the right and left bronchus. They divide to form smaller tubes called bronchioles, which carry air through the lungs.

At the end of the bronchioles, there are millions of tiny air sacs called alveoli. In the alveoli, oxygen is absorbed from the air we breathe in and passes into the bloodstream to be circulated around the body.

Carbon dioxide is a waste gas that needs to be removed from the body. It passes from the bloodstream into the alveoli and is then breathed out by the lungs.

Just below your lungs is a sheet of muscle called the diaphragm. The diaphragm and the muscles of the lower chest are the main breathing muscles used when you are relaxed.

During heavy exercise, the muscles in your shoulders and upper chest can also help with breathing. These muscles are not designed to work for long periods of time and tire easily.

Diagram of the lungs
Diagram of the lungs

View a large version

Read a description of this image

Causes of breathlessness

There are a number of possible causes of breathlessness. Your doctor will be able to tell you the cause of your breathlessness so that you can get the most helpful treatment. In this section, we describe common causes, including the effect of some cancer treatments.

Cancer affecting the lungs

This can be a primary lung cancer (cancer that started in the lungs) or a secondary cancer that has spread to the lung from another part of the body. Treatments such as radiotherapy or chemotherapy may help shrink the tumour and relieve any breathlessness caused by the cancer. We can send you information about the type of cancer you have and its treatments.

A build-up of fluid in the lining of the lungs (pleural effusion) or stomach (ascites)

If cancer cells irritate the lining of the lungs or stomach, this can cause a build-up of fluid. This means there is less room for the lungs to expand. Pleural effusion and ascites can be treated by removing (draining) the fluid.

Low levels of red blood cells in the blood (anaemia)

This can be due to the cancer or its treatment, including chemotherapy and radiotherapy. Red blood cells carry oxygen around the body. If the level of red blood cells in your blood is low, you may become very tired and breathless.

Your doctors may recommend that you have a blood transfusion.

Chest infections

These cause phlegm in the airways and can make you feel breathless. It’s important to drink a good amount of fluid to dilute the phlegm so you can cough it up more easily. If you develop a raised temperature (above 38°C or 100.4°F), a chesty cough or pain when you breathe, contact your doctor immediately as you may need antibiotics.

Weakened muscles

In advanced cancer, the muscles that help breathing can become weak because of reduced physical activity, fatigue, lack of nutrition and weight loss. This can make breathing more difficult.


Pain that’s poorly controlled can make it difficult to breathe and move comfortably. Tell your doctor about any pain you’re experiencing so they can make sure it’s being managed.

A blood clot in the lung (pulmonary embolism)

This can cause sudden breathlessness and pain when you breathe. If you have these symptoms, contact your doctor immediately.

Other conditions

Some other conditions can cause breathlessness, such as congestive heart failure, asthma, chronic obstructive pulmonary disease (COPD) and pulmonary oedema (a build-up of fluid in the lungs). Your doctor can advise you on the treatment you need.

Smoking tobacco

Smoking makes breathlessness worse. The smoke causes irritation and inflammation of the airways. As a result, less oxygen gets absorbed into the bloodstream. If you want to stop smoking, ask your nurse or doctor about help that’s available locally, such as free local NHS Stop Smoking Services. You can also call our cancer support specialists for more advice.

Anxiety and panic

Feelings of anxiety and panic are common. They’re natural reactions following a cancer diagnosis and during treatment. However, they can cause some people to have rapid and shallow breathing. Becoming breathless can itself cause further anxiety and panic.

Cancer treatments

Surgery for lung cancer may remove part, or all, of a lung. Many people are able to breathe well after they recover from surgery, but some people do experience breathing problems.

Radiotherapy to the chest can cause inflammation of the lung (pnuemonitis), which can lead to breathlessness. This is usually a short-term problem, but some people can have it in the long-term. Sometimes, people who have intensive radiotherapy to the chest can develop hardening and thickening (scarring) of the lung, which can cause long-term breathlessness.

Chemotherapy drugs can also sometimes cause breathing problems.

Your cancer specialist can tell you about any effects your treatment may have on your breathing and answer any questions you have. If you experience breathlessness, always let your doctor know.

Indicating how breathless you are

Using a Borg scale can help you to indicate to others how breathless you are.

Using a Borg scale

When you become breathless, it may help to give your family, friends and healthcare professionals a clear idea of how bad the breathlessness is. This can help them to understand how much support you need at the time. A Borg scale can be used to give your breathlessness a number – with 0 being no breathlessness at all and 10 being the most severe breathlessness.

A Borg scale can also help you to be aware of your breathing and how it changes, especially when carrying out activities.

You might want to point to the scale during episodes of breathlessness, to communicate to others how you’re feeling when you don’t want to use your breath to talk. Here's a Borg scale to help you indicate to those around you how breathless you are:

0Very, very slight (just noticeable)
0.5Nothing at all
1Very slight
2Slight (light)
4Somewhat severe
5–6Severe (heavy)
7–9Very severe
10Very, very severe

Keeping a diary of breathlessness

It can be helpful to keep a note of when your breathlessness has been difficult, activities that made it worse and what techniques you used to deal with it. You may find there are certain times of the day when more energy is needed, such as in the morning when you’re getting dressed in the morning. Or you may find there are certain things that make your or that feeling stressed can make breathlessness worse, such as feeling stressed.

You can also use a diary to plan activities for times of the day when you feel better, and to remind you to practise breathing, controlled breathing and relaxation techniques.

Your feelings about breathlessness

Many people feel down at various times during their illness. Some days you may feel well and relaxed, while on others you may feel frightened, stressed, angry, sad and even guilty. Having a range of emotions is a normal response to breathlessness, the cancer, the treatment and any fears you have about the future. There’s no right or wrong way to deal with these feelings but accepting they are normal will help.

Sometimes you may feel that you need to be alone, while at other times you may want to be with people. Go with what feels right for you at the time where possible. You may have family and friends who find your changing emotions difficult to understand, but if you talk together about how each of you feel, you’ll understand each other better and be able to cope with the problems more easily.

You may find it helpful to talk to other people who are going through similar experiences. You can find out about support groups in your area by calling our helpline us or visiting the support group section on our website. You can also share your experiences of breathlessness with others on our Online Community.

Feeling depressed about breathlessness

Many people feel sad as a result of their cancer and difficult symptoms such as breathlessness. This is a natural response. Sometimes, these feelings of sadness don’t seem to pass but get worse, and you may become depressed.

Depression can come on gradually and may be difficult to recognise. If you’re depressed, it may be more difficult for you to follow your health professional’s advice or treatment.

Depression can usually be successfully treated in most people. The first step to feeling better is getting appropriate help. If you or your family think you may be depressed, discuss it with your GP. They can prescribe an antidepressant drug for you or refer you to a doctor or counsellor who specialises in the emotional problems that people with cancer might experience. By getting depression treated, you will make life easier for yourself, your friends and family.

Feeling isolated

People with breathlessness can sometimes become isolated if they are less able to go out to meet family or friends. Talking in a large group of people can also be very tiring.

You may feel that you would rather avoid these types of social situation. If you do feel isolated, it may help to talk to your family and friends. Tell them how you feel and how much you’re able to do. Together, you may be able to find a way to continue seeing each other that is less tiring for you.

Find out more about the emotional effects of cancer.

Back to Breathlessness

Relaxation techniques

You may want to try using relaxation techniques to help you manage your anxiety and reduce breathlessness.