Side effects – how chemotherapy affects the blood

Blood cells are made in the bone marrow, which is in the middle of your bones. Chemotherapy can damage the bone marrow, which reduces the number of blood cells made. This can cause side effects.

There are three main types of blood cell.

• White blood cells fight infection. The most common type of white blood cell is called a neutrophil.
• Red blood cells carry oxygen around the body. The part of the cell that carries the oxygen is called haemoglobin.
• Platelets are tiny cells that help the blood to clot.

You will have regular blood tests, called a full blood count, to check your blood cell levels. If the number of blood cells drops, the main side effects are:

• risk of an infection, from a low level of white blood cells (neutropenia)
• anaemia from a low level of red blood cells, or low haemoglobin
• bleeding or bruising from a low level of platelets (thrombocytopenia)

Depending on the test results your oncologist might want to wait an extra week or so for your blood cell levels to recover. Or they may decide to lower the dose of the chemotherapy so that your treatment can continue. This is quite normal with chemotherapy and nothing to worry about. It will not affect your treatment and is the best way to make sure you have chemotherapy regularly and feel as well as possible.

Infections

A low level of white blood cells may mean that your body is less able to fight an infection.

An infection is an emergency if you are having chemotherapy. It can be life threatening and needs treating straight away, as it won’t get better without medical help. Don’t ignore the signs of an infection.

Signs of an infection include:

• a high or low temperature – your chemotherapy team will tell you what to watch out for
• feeling shivery and cold
• headaches
• sore muscles
• a cough or sore throat
• pain or burning when you pee
• feeling generally unwell or tired.

Antibiotics can be used to treat an infection. Your chemotherapy may be delayed until your infection has been treated.

Ask your chemotherapy team if you need any vaccinations before your chemotherapy. You should avoid any dental treatment once you start chemotherapy, as this can increase your risk of getting an infection. If you do need urgent dental care, speak to your oncologist first, and make sure you tell your dentist you are having chemotherapy.

Your oncologist may give you an injection called G-CSF (granulocyte-colony stimulating factor) during your chemotherapy. This can help prevent infection as it helps your body make more white blood cells. It isn’t used with all chemotherapy drugs, so your oncologist will speak to you about whether you will have it.

Can I take paracetamol or ibuprofen while having chemotherapy?

Paracetamol and ibuprofen can be used to help manage pain. But they can also lower your temperature. This can hide the symptoms of an infection and make you feel better but it won’t treat the infection.

Always check your temperature before taking these painkillers. If it is high, call the 24 hour emergency number straight away.

Anaemia

Some chemotherapy drugs can lower the number of red blood cells in the blood. This is called anaemia. It can make you feel tired, weak, faint and short of breath.

If your red blood cell level is very low, you may need to be given blood through a drip. This is called a blood transfusion and will increase your red blood cell levels.

Bleeding and bruising

Chemotherapy can lower the number of platelets in your blood. This is called thrombocytopenia. Platelets are cells that help blood to clot. If the number of platelets drops, you may be more likely to have nosebleeds, bleeding gums or tiny red spots on your skin. You may also bruise more easily than normal. If you have a nosebleed that doesn’t stop after five minutes, call the emergency number.

Updated May 2024

Review date October 2026