You might have radiotherapy for:

  • a tumour that started in the brain (a primary brain tumour)
  • cancer cells that have spread to the brain from another part of the body (secondary brain tumour)

Like all side effects of radiotherapy, you might not feel tired straight away. It tends to come on gradually as you progress through your treatment and for a few weeks afterwards. 

Radiotherapy can cause tiredness because the body is using up your energy reserves to repair healthy cells damaged by the radiotherapy. If you are taking steroids, you might also find that you feel extremely tired when you stop taking them. Travelling to the hospital each day for treatment can also make you tired.

Everyone reacts differently to radiotherapy, so how tired you feel varies from person to person. 

Coping with tiredness

You might feel weak and lack energy as well as being tired. It can sometimes help to sleep for a short time during the day. Rest when you need to.

Various things can help you to reduce tiredness and cope with it, for example, exercise. Some research has shown that taking exercise can give you more energy. It is important to balance exercise with resting.


In a few people, the tiredness can become very severe a few weeks after treatment has finished. You may also feel drowsy and irritable. This is a rare side effect and is sometimes called hypersomnia. 

It is extreme tiredness that can make you feel very drowsy and want to sleep a lot. You might also have:

  • headaches
  • a high temperature
  • loss of appetite
  • feeling and being sick (nausea and vomiting)

If you are sleeping a lot or have these symptoms and are worried, contact the team looking after you. 

  • Drug therapy for the management of cancer-related fatigue
    O Minton and others
    The Cochrane Database of Sytematic Reviews (2010)

  • Efficacy of exercise interventions in modulating cancer-related fatigue among adult cancer survivors: a meta-analysis
    J C Brown and others
    Cancer Epidemiology, Biomarkers and Prevention (2011)

  • Cancer Priniciples & Practice of Oncology (11th edition)
    V T DeVita and others 
    Wolters Kluwer (2019)

Last reviewed: 
10 Nov 2019
Next review due: 
10 Nov 2023

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