Causes of fever

Other causes of fever

There are other reasons why you might get a fever when you have cancer. This includes your treatment, drug side effects, blood or blood products or a blockage in your bowel.

Drug side effects

Having a fever doesn’t always mean you have an infection. Some drugs can affect your body’s ability to control temperature. So you may have side effects like fever, shivering or chills.

If you get a fever while you are having a drug through a drip your nurse might need to stop or slow down the infusion. It will depend on how you react to the drug. Drugs affect people in different ways and not all people will develop a fever.

You may need medicine like paracetamol, antihistamine, or steroids to help you if you have a reaction.

You should always call your healthcare team straight away if you have a fever. They can find out if it is a drug side effect or an infection.

Go to our drugs A to Z to find out about side effects

Blood or blood products

You might have a reaction to a blood or blood product transfusion. The first sign is often fever and shivering. It happens because the donated blood or blood products contain cells and antibodies from the donor's immune system. Your body can react to these cells because they are different to your own cells.

Doctors try to lower the risk of transfusion reactions for patients most at risk. For example, if you're having a blood transfusion, they can irradiate the blood before transfusing it. Your nurse or doctor will explain more about this if you have irradiated blood.

Your nurses will keep a close eye on you for any signs of a reaction. It's not uncommon for your temperature to go up slightly when you have a transfusion. This is not the same as having a reaction. Your nurse will immediately stop your transfusion and give you any necessary treatment if you do react.

You might worry that the blood transfusion itself will give you an infection. This is extremely rare, as all blood is very carefully screened.

Remember transfusions are generally safe and do not normally cause any problems.

A blockage in your bladder or bowel

When a blockage (obstruction) occurs in your bowel (intestine) or bladder, waste matter is not able to move through as it normally does. This means bacteria can start to grow and cause an infection.

Other conditions

Some other medical conditions can cause fever. This includes:

blood clots
some disorders of the connective tissue
hepatitis (inflammation of your liver)
Crohn's disease (a condition causing inflammation of your gut)

Last reviewed: 24 Mar 2026

Next review due: 23 Mar 2029

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.

Relieving the symptoms of fever

A fever can make you feel hot, cold, shivery, and washed out. Treating the cause and relieving the symptoms can make you feel better.

Infections

Fever can be caused by infection. Find out what can be done to control and treat your fever.

Sepsis, infection and cancer

Sepsis is a serious complication of an infection that can be life threatening. Fever might be the first sign of an infection, or you might have other symptoms.