Anaemia, chest infection and other causes

If you are short of breath, it might not be due to cancer. It might be caused by other medical conditions or other factors.


Red blood cells are made in your bone marrow. They contain haemoglobin (Hb). This is what carries oxygen around your body.

If the level of haemoglobin in your blood is low, you have anaemia. An important part of haemoglobin is iron. So your doctor may say you are low in iron if you are anaemic.

Anaemia makes you very tired and you may also become breathless because your blood is carrying less oxygen.

Anaemia can be a side effect of cancer treatments such as chemotherapy and radiotherapy. Or your cancer itself can cause anaemia.

If this is the cause of your breathlessness, treatment for your anaemia can help you to feel less breathless.

Chest infection

Your bone marrow makes white blood cells. These cells are part of your immune system and help your body to fight infection. 

Cancer cells and cancer treatment can damage your bone marrow. If you don't have enough white blood cells, you have a higher risk of getting an infection. 

Having a chest infection will affect the way you breathe. If you have a serious infection, such as pneumonia, breathing will be even harder. 

Infection during cancer treatment can be very serious (even life threatening). Contact your doctor immediately if you have a temperature or other signs of infection.

Tumour growth

Cancer in or near your lungs might put pressure on your airways, or start to block them. This might narrow the tubes carrying air into your lungs, making it difficult for air to come through. This will make it difficult to breathe normally. 

A blockage in the upper airways can cause noisy breathing. This is called stridor. You might be able to hear the air going in and out past the blockage.

Other causes

Medical conditions 

Breathlessness can be caused by:

  • lung diseases such as emphysema, chronic obstructive pulmonary disease (COPD)
  • asthma
  • heart problems such as congestive cardiac failure (CCF) 
  • blood clots
  • pain 
  • a collpased lung

Other factors 

  • smoking
  • being overweight (obesity)
  • anxiety and emotional problems
Talk to your doctor about the cause of your breathlessness and the best treatment for you.
Last reviewed: 
19 Nov 2019
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  • Palliative procedures in lung cancer

    E Masuda and others (2013) 

    Seminars in interventional radiology Jun;30(2):199-205

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