Finding the cause of your fever

It's important to try and find out what is causing your fever. This helps doctors choose the right treatment for you.


Your doctor will want to examine you and ask you a number of questions if you develop a fever. This is so they can find out the exact cause of the fever and treat it in the best way. 

They might ask:

  • When did the fever start?
  • What symptoms do you have?
  • What cancer treatments are you having?
  • How long is it since your last treatment?
  • Do you have any difficulty passing urine or opening your bowels?
  • What medications are you taking?
  • Do you have any pain? If so, where?
  • Do you have any lines into your veins (for example a PICC line or central line)?
  • Do you have any tubes, drains or catheters?
  • Is the fever there all the time, or does it come and go?
  • Do you have night sweats?
  • Do you have any wounds that have not completely healed?
  • Do you have any other illnesses?
If you have a fever you should contact your 24 hour advice line straight away. You should see a healthcare professional with experience in managing infections after cancer treatment within 24 hours of being in hospital. They assess your risk of becoming very unwell because of an infection.


Your doctor will examine you if they suspect you have an infection. 

Sometimes your signs and symptoms can give your doctor some idea as to where in your body your infection is. For example, if you have burning and stinging sensations when passing urine, then you might have a bladder infection.

Your doctor will also check your breathing and you may have a chest x-ray to rule out lung infection. They will carefully examine the entry site of your drip or central line for any signs of infection, if you have one.

You'll have blood samples taken. This is to check that your blood cell counts are normal. And to look for infection in your blood. This test is called blood cultures.

You might also have other tests to check for infection from your:

  • urine
  • spit (sputum)
  • wound sites

What happens if your team can't find the cause

It's not always possible for your doctor to find out exactly what is causing your fever. So you’re usually treated with a type of antibiotic that is active against a wide variety of bacteria. This is called a broad spectrum antibiotic.

You might need to have some tests repeated. And you may need your antibiotics changed if tests show up a bacteria that needs to be treated with a specific antibiotic, or if you become more unwell.

It's important that your doctor keeps checking to find the cause, but some infections are very hard to find. You may get better with antibiotics before your doctor can pinpoint the cause.

Last reviewed: 
05 Aug 2019
  • Cancer: Principles and Practice of Oncology (11th Edition)
    V T Devita, T S Lawrence and S A Rosenberg
    Lippincott Williams and Wilkins, 2019.

  • Management of Febrile Neutropaenia: ESMO Clinical Practice Guidelines
    J Klastersky and others
    Annals of Oncology, 2016. Volume 27, Issue 5, Pages v111- v118.

  • Neutropenic sepsis: prevention and management of neutropenic in people with cancer
    National Institute for Health and Care Excellence, September 2012.

  • Cancer and its management (7th edition)
    J Tobias and D Hochhauser 
    Wiley-Blackwell, 2015.

  • The pathophysiological basis and consequences of fever
    E J Walters and others
    Critical Care, 2016. Volume 20, Page 200.

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. If you need additional references for this information please contact with details of the particular risk or cause you are interested in. 

Related links