Infection during or after treatment

Having cancer or treatment for cancer can weaken your immune system. This makes it more likely that you will pick up an infection and develop a fever.


What is chemotherapy?

Chemotherapy is a type of anti cancer drug treatment. It travels around your bloodstream and works by killing cancer cells.

Chemotherapy drugs also affects healthy cells such as white blood cells. Your bone marrow produces these and they're important to help fight off infection.

Chemotherapy and infection

After chemotherapy, if your white blood cells are low, you're more likely to get infections. Any infection can also worsen quite quickly. Because of the chemotherapy your immune system isn’t as good as before. So simple infections can now become life threatening within hours if not treated.

Your nurse or doctor will tell you about the symptoms of infection to look out for, and when you need to call your advice line or return to hospital.

Not all chemotherapy drugs affect your bone marrow and increase the risk of infection, but many do. It depends on:

  • which drug you have
  • the amount (dose) of the drug – the higher the dose the more likely it is to affect your bone marrow
  • your age – chemotherapy is more likely to affect your bone marrow function if you are elderly
  • your general health
  • the type and stage of your cancer

When you are most at risk

These effects on your bone marrow usually begin around 7 to 14 days after each treatment. This is when your blood counts are usually at their lowest point. This is called nadir. They usually return to normal between 21 and 28 days.

When your blood cell counts are at their lowest you can feel very tired (fatigued). Some people also say they feel depressed. This can be really hard to deal with and make you wonder if you really want to go on with your treatment. This is usually because it is also affecting your red blood cells.

Things should improve as your blood counts rise. You'll start to feel better again before your next treatment. Unfortunately, they'll go down again after each treatment. But once your treatment is finished your blood cell counts will return and stay at normal levels.

To make sure your bone marrow is working well you will have regular blood tests. Sometimes your doctor may give you a course of antibiotics during your chemotherapy to help fight off an infection or stop you getting one.


What is radiotherapy?

Radiotherapy uses x-rays to treat cancer cells. Radiotherapy destroys the cancer cells in the treated area. Healthy cells are also affected by radiation if they're in the treated area.  

Radiotherapy and infection

Radiation can also affect the cells in your bone marrow, which produce your blood cells, including the white blood cells. But generally, radiotherapy only affects the area being treated and is less likely to affect your white blood cells than chemotherapy.

Who is most at risk

Treatment to a large area of your body, or treatment to the bones of the legs, chest, abdomen or pelvis, will mean your bone marrow is more likely to be affected. People having total body irradiation before a stem cell or bone marrow transplant will be severely affected and will have low red cells, white cells and platelets.

You'll have regular blood tests during and after your treatment to check your blood cell count. 


Infection is a possible side effect of any type of surgery. Or any procedure that involves cutting the skin such as having a central line or drain in. The risk of infection depends on what type of surgery or procedure you have.

You might have antibiotics to reduce the chance of getting an infection after your operation or procedure. After an operation, you may have drainage tubes in place to stop fluid from collecting around the operation site. This is important because, as well as being uncomfortable or painful, fluid that does not drain away can be a site of infection.

Surgery does not weaken your resistance to infection nearly as much as chemotherapy or a stem cell or bone marrow transplant.

You’ll be taught how to look after your wounds and when to you should tell your medical team if there are any concerns.


Immunotherapy uses our immune system to fight cancer. It works by helping the immune system recognise and attack cancer cells.

Immunotherapy uses substances involved in fighting infection. These substances are called cytokines. They are a group of proteins in the body that play an important part in boosting the immune system.

When you get an infection the body produces cytokines. These help to control and direct the immune system to the infection. They are responsible for some of the symptoms of infection such as fever.

When you have immunotherapy you get larger amounts of cytokines in your body than you would normally make. This seems to be the reason why symptoms such as fever can be a side effect of some of these cancer treatments.

Stem cell and bone marrow transplants

What are transplants?

Stem cell or bone marrow transplants is a cancer treatment to try and cure some types of cancer. Some of these cancers include leukaemia, lymphoma and myeloma.

Stem cells are very early cells made in the bone marrow. Bone marrow is a spongy material that fills the bones and is the body’s factory for making cells. These stem cells develop into red blood cells, white blood cells and platelets. 

For the transplant, you have very high amounts of chemotherapy, sometimes with targeted cancer drugs. You might also have radiotherapy to the whole of your body. This is to try and kill off the cancer cells.

The high doses damage your bone marrow, so you need a bone marrow or stem cell infusion to replace the bone marrow cells you’ve lost.

Transplants and infection

You'll have a very low white blood cell count for quite a while after having a transplant. This means you are more at risk of getting an infection. This is most likely to be from the normally harmless bacteria we all have in our digestive systems and on our skin. 

This is quite an intensive treatment so you usually have antibiotics and anti fungal medicines to prevent infections. It’s also important that you follow the information from your medical team about diet and personal hygiene.

Graft versus host disease (GvHD)

Graft versus host disease (GvHD) is a transplant side effect that some people get when they have stem cells or bone marrow from somebody else. GvHD can range from being mild to very serious. Although it is not an infection, it often causes a fever. Treatments for GvHD, such as steroids and drugs which affect your immune system, can increase your risk of getting an infection.

Last reviewed: 
02 Aug 2019
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