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Finding the cause of your fever

It is 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 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?
You need to go back to hospital straight away if your white blood cells are low after cancer treatment and you get a fever. 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.

Your doctor will arrange for you to have a blood sample 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 tests to check for infection:

  • in your urine
  • in your sputum
  • from any wound sites
  • from the exit site of any intravenous lines, such as a PICC line

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. Doctors cannot find the cause of infection in half of those (50%) with cancer who have an infection.

You can still be treated with a broad spectrum antibiotic. This is a type of antibiotic that is active against a wide variety of bacteria.

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.

Some infections are very hard to find and it's important that your doctor keeps checking to find the cause.

Last reviewed: 
28 Jun 2017
  • Cancer: Principles and practice of oncology (10th edition)
    VT DeVita and others
    Lipincott Williams and Wilkins, 2015

  • Management of febrile neutropenia: ESMO Clinical Practice Guidelines

    J de Naurois and others, 2010

    Annals of Oncology, Volume 21, Supplement 5

  • Neutropenic sepsis: prevention and management of neutropenic sepsis in cancer patients

    National Institute of Health and Care Excellence (NICE), September 2012

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