Possible side effects of chemotherapy for CUP

Chemotherapy treatment can cause different side effects. These vary depending on the drugs you have.

Some side effects are more common than others but you won’t have them all. Chemotherapy mainly causes side effects in areas of your body where new cells are being quickly made and replaced. This includes the:

  • bone marrow (where blood cells are made)
  • hair follicles (where hair grows from)
  • digestive system
  • lining of your mouth.

Your cancer doctor and nurse specialist will explain the side effects that your chemotherapy is likely to cause. Most side effects can be reduced and controlled with drugs. Your doctor or nurse can tell you how to manage them.

Most side effects stop or gradually go away when chemotherapy is over.

Side effects

Chemotherapy drugs may cause unpleasant side effects, but these can usually be well controlled with medicines and will usually go away once treatment has finished. Not all drugs cause the same side effects and some people may have very few. You can talk to your doctor or nurse about what to expect from the treatment that’s planned for you.

Risk of infection

This treatment can reduce the number of white blood cells in your blood. These cells fight infection. If the number of white blood cells is low, you are more likely to get an infection. A low white blood cell count is called neutropenia.

If you have an infection, it is important to treat it as soon as possible. Contact the hospital straight away on the 24-hour contact number you have if:

  • your temperature goes over 37.5°C (99.5F)
  • you suddenly feel unwell, even with a normal temperature
  • you have symptoms of an infection.

Symptoms of an infection include:

  • feeling shivery
  • a sore throat
  • a cough
  • diarrhoea
  • needing to pass urine often.

It is important to follow any specific advice your cancer treatment team gives you.

The number of white blood cells will usually return to normal before your next treatment. You will have a blood test before having more chemotherapy. If your white blood cell count is low, your doctor may delay your treatment for a short time.

Bruising and bleeding

Chemotherapy can reduce the number of platelets in your blood. Platelets are cells that help the blood to clot. If you develop any unexplained bruising or bleeding, such as nosebleeds, bleeding gums, blood spots or rashes on the skin, contact your doctor or the hospital straight away.

Anaemia (reduced number of red blood cells)

If chemotherapy reduces the number of red blood cells in your blood, you may become very tired and feel you have no energy. You may also become breathless and feel dizzy and light-headed. These symptoms happen because the red blood cells contain haemoglobin, which carries oxygen around the body.

If your haemoglobin is low you may be offered a blood transfusion. You’ll feel more energetic and any breathlessness will be eased.

Tiredness (fatigue)

You’re likely to become tired and have to take things slowly. Try to pace yourself and save your energy for things that you want to do or that need doing. Balance rest with some physical activity – even going for short walks will help increase your energy levels. We have helpful tips on coping with tiredness.

Feeling sick or being sick

Some chemotherapy drugs can make you feel sick (nauseated) or possibly be sick (vomit). Your cancer specialist will prescribe anti-sickness (anti-emetic) drugs to prevent this. Let your doctor or nurse know if your anti-sickness drugs are not helping, as there are several different types you can try. We have more information about controlling nausea and vomiting.


Some of the chemotherapy drugs can cause diarrhoea. This often starts several days after treatment. If you’re taking chemotherapy tablets or capsules at home, it's important to let your doctor or nurse know if you have diarrhoea as your treatment may need to be interrupted. Medicine can be prescribed to help. It’s important to drink plenty of fluids if you have diarrhoea. We have more information about managing diarrhoea.

Sore mouth

Chemotherapy can cause mouth problems such as a sore mouth, mouth ulcers or infection. Drinking plenty of fluids, and cleaning your teeth regularly and gently with a soft toothbrush can help to reduce the risk of this happening. Your chemotherapy nurse will explain how to look after your mouth to reduce the risk of problems. They can give you mouthwashes, medicines and gels to help.

We have some useful tips on coping with a sore mouth during chemotherapy.

Hair loss

Some chemotherapy drugs may cause hair loss. Some people may have complete hair loss including eyelashes and eyebrows. Others may only experience partial hair loss or thinning. It depends on what chemotherapy drugs you are having (your doctor or nurse can tell you more about what to expect). If you do experience hair loss your hair should start to grow back within about 3–6 months of the end of treatment. It may grow back straighter, curlier, finer, or a slightly different colour than it was before. Your nurse can give you advice about coping with hair loss and how to look after your scalp.

Some chemotherapy departments may offer scalp cooling to reduce hair loss during chemotherapy. We have more information about coping with hair loss.

Numbness or tingling in hands or feet

This is due to the effect of certain chemotherapy drugs on the nerves and is known as peripheral neuropathy. Tell your doctor if you notice these symptoms. This problem usually improves slowly over a few months after the treatment is over.

Early menopause

If you are a woman who hasn’t been through menopause, you may find that chemotherapy makes it happen early. Signs of this are hot flushes and sweats. Some women can have hormone replacement therapy (HRT), which may help relieve symptoms. We have more information about the menopause.


Men who might possibly father a child, or women who might become pregnant, should use effective contraception during their course of chemotherapy treatment. This is because the drugs might harm a baby conceived during this time. It is important to carry on using effective contraception after your treatment finishes, for up to a year afterwards. You can discuss this with your doctor or specialist nurse.

A barrier contraception such as a condom should be used during sex within the first 48 hours after chemotherapy. This is to protect your partner from any of the drug that may be present in semen or vaginal fluid. You can discuss this with your doctor.


Some chemotherapy drugs can cause infertility. Infertility is the inability to become pregnant or to father a child. This may be temporary or permanent, depending on the treatment that you have. If this is a concern for you, it is important to discuss your infertility risk with your cancer doctor before you start chemotherapy.

Back to Side effects of chemotherapy

Late effects of chemotherapy

Late effects are side effects you still have six months after chemotherapy, or side effects that begin years later.