Possible side effects of radiotherapy

Your radiotherapy team plans your treatment carefully to reduce your risk of side effects. But most people have some side effects during or after radiotherapy.

Side effects do not usually happen straight away. They may develop during treatment or in the days or weeks after treatment finishes. Sometimes side effects get worse for a time during and after you have finished radiotherapy before they get better. There may also be a risk of side effects that are long-term or that only start months or years after radiotherapy.

It is difficult to know exactly how you will react to treatment. Your team will explain what to expect. Always tell them if you have side effects during or after radiotherapy. They can give advice and support to help you cope.

Below are some of the general radiotherapy side effects. You are unlikely to get all of them. You may also get other side effects that we do not mention here. This can depend on:

  • the area of your body being treated
  • the type of radiotherapy you have
  • other treatments you are also having, such as chemotherapy.

Radiotherapy only affects the area of the body being treated. You may find it helpful to read our information about the type of cancer you have. This has more detail about your treatment and the other possible side effects.

We also have more information about side effects that may affect your sex life and fertility for men and women.

Booklets and resources

Tiredness (fatigue)

Radiotherapy can make people feel tired. Tiredness may get worse as treatment goes on. You might be more tired if you have to travel to the hospital every day or if you are having radiotherapy alongside other treatments, such as surgery or chemotherapy.

Some people are able to continue with their daily activities. Others may find they need to rest more.

After treatment finishes, you may continue to feel tired for weeks or months. If it does not get better, tell your cancer doctor or specialist nurse.

Some people who have advanced cancer may have external beam radiotherapy to help control symptoms of the cancer. This is called palliative radiotherapy. As well as tiredness, this might also cause some mild aches and pains. This usually gets better over a few days.

Coping with tiredness

Here are some tips for coping with tiredness.

  • Get plenty of rest.
  • Do some gentle exercise, such as going for short walks. This gives you more energy and keeps your muscles working.
  • Try to eat a healthy diet and drink plenty of fluids.
  • Save some energy to do the things you enjoy.
  • Ask for help with everyday tasks, if you have friends or family members who can support you.

We have more information about coping with tiredness.

Problems with eating and drinking

At times during your treatment, you may not feel like eating. Or you may find that your eating habits change. Eating a healthy diet and drinking plenty of fluids is good for your general health. Tell your team if you are finding it difficult to eat.

Radiotherapy to some areas of the body can cause more serious side effects that may make eating and drinking difficult. This includes treatment to your head, neck or oesophagus. Your team may suggest putting a feeding tube into your stomach. You may have one of the following tubes:

  • A NG tube – this is passed down the nose and into the stomach.
  • A PEG or RIG tube – this tube is passed through the skin and muscle of the tummy (abdomen) and into the stomach during a small operation.

The tube is usually put in before your treatment starts. You usually only need it for a short time. You can be fed through it if you have problems eating or drinking. When you can eat and drink again, it is taken out.

Coping with eating and drinking problems

Tell the radiotherapy team if you are having any problems. They can give you advice. They may be able to arrange for you to talk to the hospital dietitian. The dietitian can monitor your weight and diet more closely.

Here are some tips for coping with eating problems:

  • Try having small, nutritious snacks throughout the day rather than large meals.
  • If food seems tasteless, use seasoning or strong-flavoured sauces.
  • It can help to avoid foods that are spicy or very hot in temperature.
  • If your mouth is dry, try sipping water regularly or chewing sugar-free gum.
  • If you are losing weight, add extra energy and protein to your diet. Or ask your radiotherapy team about using food supplements.

We have more information about managing eating problems.

Feeling or being sick

Some people find radiotherapy makes them feel sick (nausea) or be sick (vomit). This is more likely if the treatment area is near the stomach or the brain.

Sickness can usually be well controlled and stops once treatment is finished. Your healthcare team may give you anti-sickness drugs to prevent nausea or vomiting.

Coping with feeling sick

Always tell your radiotherapy team if you have nausea or vomiting during or after your treatment. They can give you anti-sickness drugs or change the drugs you are taking. They will explain when and how to take the drugs.

These drugs often work better when you take them regularly, or before you start to feel sick. Tell your team if the sickness does not get better.

Here are some tips for coping with feeling sick:

  • Ask for help with cooking and preparing meals, if you have friends or family members who can do this for you. This may help, especially if the smell of cooking makes you feel sick.
  • Sipping drinks slowly, drinking ginger tea, or eating ginger biscuits may also help.

We have more information about coping with feeling and being sick.

Skin reactions

External beam radiotherapy can cause a skin reaction in the area being treated. If this happens, it usually begins after about 10 days.

You may find your skin in the treatment area becomes red or darkens. It may also feel sore or itchy. Sometimes the skin gets very sore and it may blister, break or leak fluid. Very rarely, your team may stop treatment for a short time to allow a serious skin reaction to recover.

Skin reactions can take time to improve. They are usually better about 4 weeks after your treatment has finished. The area of skin may always look or feel slightly different to the surrounding skin.

Coping with skin reactions

During your treatment, you are usually advised to:

  • wear loose-fitting clothes made from natural fibres, such as cotton
  • wash your skin gently with soap and water and gently pat it dry
  • avoid rubbing the skin
  • avoid very hot things, for example heating pads
  • avoid cooling pads but these may be helpful in some situations so speak to your team about using these first
  • avoid wet shaving
  • avoid hair-removing creams or products, including wax and laser treatment
  • follow your radiotherapy team’s advice about using moisturisers and deodorants
  • protect the treated area from the sun – your radiographer can give you more information about this.

If your skin becomes sore or itchy or changes colour, tell your radiotherapy team as soon as possible. They can give you advice and treatments if needed.

After radiotherapy

When you finish radiotherapy, you should protect the skin in the treated area from strong sunshine. Once any skin reaction has disappeared, use a suncream with a high SPF of at least 50.

Wear close-weave clothing and a wide-brimmed hat to protect your head and neck area. Remember, you can burn through clothing if you are out in hot sun for a long time. Your radiographer can give you more information about this.

You may be able to go swimming once any skin reaction has disappeared. Your radiographer can give you information when it is safe to go swimming after radiotherapy. Remember to use a waterproof suncream if you swim outdoors.

Hair loss

Radiotherapy only causes hair loss in the treatment area. You may lose your hair where the radiation beam leaves the body as well as where it enters the body. Ask your cancer doctor or radiographer to show you exactly where your hair is likely to fall out.

Hair may start to fall out 2 or 3 weeks into radiotherapy treatment. It usually grows back after treatment finishes. Sometimes it grows back a different texture or colour than before. It may take several months to grow back, depending on the dose of radiotherapy you have.

Rarely, hair does not grow back or is patchy. Your doctor or radiographer can tell you if this is likely with your treatment.

Coping with hair loss

If you are worried about losing the hair on your head, it may help to read our information about coping with hair loss. This includes tips to help you prepare if you are likely to lose your hair. Your team can give you information about getting a wig.

Changes in your blood

Some treatments can reduce the number of normal blood cells produced by your bone marrow. Bone marrow is the spongy part inside some bones.

Treatments that impact blood cells include some types of radioisotope therapy. Sometimes, it can also happen with external beam radiotherapy, especially if you have chemotherapy at the same time.

Your blood cell levels are unlikely to cause problems. They will also improve after your treatment finishes. But some people need treatment if the level of certain types of blood cells is too low.

Your team will arrange any blood tests you need during and after your treatment. Always tell your team if you have any bruising or bleeding that you cannot explain. This includes:

  • nosebleeds
  • bleeding gums
  • heavy periods
  • blood in your urine (pee) or stools (poo)
  • tiny red or purple spots on the skin that may look like a rash.

You should also contact them straight away if:

  • your temperature goes over 37.5°C (99.5°F) or below 36°C (96.8°F)
  • you suddenly feel unwell, even with a normal temperature
  • you have symptoms of an infection.

Symptoms of an infection include:

  • feeling shivery and shaking
  • a sore throat
  • a cough
  • breathlessness
  • diarrhoea
  • needing to pass urine (pee) a lot, or discomfort when you pass urine.

Side effects of radiotherapy and sex

If you are in a relationship, try to be honest about how you feel. If cancer or treatment has changed how you feel about your body or about sex, tell your partner. This gives them the chance to understand and support you. They may also have questions to ask you. Try to listen to, and answer, each other’s questions and concerns.

Side effects of radiotherapy to any part of the body can change how you feel about having sex. You can find more information about how radiotherapy may affect your sex life in our information about your cancer type.

It is normal to be less interested in sex if you are tired, unwell or anxious. Changes such as weight loss, hair loss or skin reactions may change how you feel about your body or make you feel less confident.

It may help to remember that most of these side effects are usually short-term and get better after you finish radiotherapy. Although it can be upsetting to lose interest in sex, things usually improve as the side effects get better.

Pelvic radiotherapy

Radiotherapy to the pelvic area can cause side effects that may make having sex difficult. The pelvis is the area between the hips in the lower part of the tummy. Sometimes these effects can be long-term or happen months or years after radiotherapy. These are called late effects. Before you decide to have treatment, your team will tell you what side effects are likely.

We have information about pelvic radiotherapy and how it affects your sex life.

Coping with effects on your sex life

If you find a side effect difficult to cope with during or after radiotherapy, talk to your healthcare team. You may feel embarrassed talking about it, but your team is used to talking about these things. They can help.

They may be able to give you information or support to cope with a problem. Sometimes they can arrange for you to see other professionals, for example a specialist doctor or counsellor.

We have more information about cancer and your sex life. You can also find information and support about sex on the College of Sexual and Relationship Therapists website. If you want to talk to a cancer information nurse, call us on 0808 808 00 00.

Effects of radiotherapy on fertility

Radiotherapy to most areas of the body does not affect your ability to get pregnant or make someone pregnant. This is called your fertility.

But your fertility may be affected if you have treatment to:

  • the pelvic area – the area between the hips in the lower part of the tummy
  • the pituitary gland – a small gland at the base of the brain.

Radiotherapy to these areas can affect how your body produces the:

  • hormones (chemical messengers) needed to control sex
  • egg or sperm cells needed to start a pregnancy.

It can also cause physical changes that:

  • make it difficult to get an erection or ejaculate
  • mean you cannot get pregnant or carry a pregnancy.

Before you decide to have treatment, your team will explain any risks to your fertility. For some people, radiotherapy causes changes that get better with time. For others, the treatment they have to the pelvic area or pituitary gland causes permanent infertility.

Your team may talk to you about fertility preservation, if this is possible for you. This can mean collecting and freezing sperm or eggs. Sometimes collected eggs can be fertilised with sperm. If suitable embryos develop, these may be frozen.

Fertility preservation is not always possible. But it may mean some people who lose their fertility are still able to have a baby in the future. We have more information about fertility preservation for fertility for women and men.

Preventing pregnancy

Even if your team tell you your fertility might be affected by the treatment, it is not always possible to know when this will happen. You may still be able to get pregnant or make someone pregnant.

You should use contraception to prevent a pregnancy during your radiotherapy and for a time after. Your team can give you more information about this.

Coping with infertility

People cope with the idea of infertility in different ways. You may come to terms with it quickly and feel that dealing with the cancer is more important. Or you might find that the impact does not hit you until treatment is over.

Whatever you are feeling, there is support if you want to talk or have questions. It does not matter whether you are starting cancer treatment or had treatment in the past. You may find it helps to talk with your partner, family, friends, or religious or spiritual adviser. If you want to talk to a counsellor, your GP or cancer doctor can help to arrange this. Fertility clinics also provide counselling.

Organisations such as the British Infertility Counselling Association (BICA) can offer support and counselling to people affected by infertility. Talking to other people in a similar position may also help you feel less alone. Get in touch with our Online Community at macmillan.org.uk/community.

Late and long-term side effects of radiotherapy

Radiotherapy is carefully planned and treatments are becoming more and more accurate. This allows your team to treat the cancer while doing as little damage as possible to other parts of the body.

But there may still be a risk you will have side effects that:

  • do not get better after treatment – these are called long-term side effects
  • only start months or years later – these are called late effects.

This risk may be higher if you are also having other treatments, such as chemotherapy.

Before you decide to have cancer treatment, your team will explain your risk of developing these side effects. Even if it is not very likely, it is important that you understand and think about these long-term risks.

You can find more about possible long-term effects of radiotherapy in our information about the type of cancer you have. We also have information about the:

Second cancers

Radiotherapy may increase your risk of developing a different type of cancer later in life. A very small number of people develop another cancer because of the treatment they had.

The chance of a second cancer is small. This risk is far less than the benefits of treating the first cancer with radiotherapy.

If you are worried about your risk of developing a second cancer, talk to your cancer doctor.

About our information

  • Reviewers

    This information has been written, revised and edited by Macmillan Cancer Support’s Cancer Information Development team. It has been reviewed by expert medical and health professionals and people living with cancer. It has been approved by Senior Medical Editor, Dr David Gilligan, Consultant Clinical Oncologist.

    Our cancer information has been awarded the PIF TICK. Created by the Patient Information Forum, this quality mark shows we meet PIF’s 10 criteria for trustworthy health information.

Date reviewed

Reviewed: 01 August 2022
Next review: 01 August 2025
Trusted Information Creator - Patient Information Forum
Trusted Information Creator - Patient Information Forum

Our cancer information meets the PIF TICK quality mark.

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