Fever

Having a high temperature is extremely common. It’s part of your body’s natural response to infection. Most of the time it is nothing serious. But unexplained fever can be a symptom of leukaemia and other types of blood cancer.

• Normal body temperature is around 37°C (98.6°F). This can vary slightly from person-to-person. It can also change slightly at different times of day.
• If you have a fever, you might notice that you feel hot, cold or shivery. Your skin might look flushed or feel warmer to the touch than usual. You might feel achey.
• Children might seem floppy, listless or irritable. Their skin might look flushed and feel warm or hot when you touch it. They may be cold and shivery.
• Or you might notice you have a fever when you take your temperature.

Like all symptoms of leukaemia, fever can be caused by many things. Having an unexplained fever does not mean you definitely have leukaemia. But if you’re worried about your symptoms, it’s a good idea to see your GP.

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We don’t know exactly why people with leukaemia or other blood cancers get fever. There are a few possible causes.

• People with leukaemia or other blood cancers often have a low white blood cell count. This means they are more likely to get infections than other people. Your immune system’s response to infection can cause a high temperature.
• Cancer can activate an inflammatory response in your body. This helps your immune system fight the cancer, but it can also cause fever.

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Other things that can cause a fever include:

• Infections. These are the most likely cause of fever. They include common things like colds and flu.
• Allergies.
• Some vaccinations.
• Reactions to blood transfusions or some medicines.
• Blood clots.
• Other types of cancer.

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If you have a fever that lasts for more than 3 days, make an appointment with your GP.

Some signs that you should contact your GP include a fever that:

• Lasts for 3 days or more
• Does not go away after taking paracetamol
• Is accompanied by other symptoms of leukaemia
• Comes and goes in a recurring pattern

Your GP will examine you to look for signs of infection or other causes of fever. They might ask for samples of your pee, poo or spit to send for tests.

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We used an AI tool to help identify relevant evidence sources for this webpage, such as scientific journals and clinical guidelines. A human checked the reliability of these sources.