Radiotherapy – possible side effects

You may develop side effects while you are having your radiotherapy treatment. These usually disappear gradually over a few weeks or months after treatment finishes. Your doctor, radiographer or nurse will discuss this with you so you know what to expect. Let them know about any side effects you have during or after treatment, as there are often things that can be done to help.


Not everyone feels tired during radiotherapy treatment but many people do. If you feel tired, get plenty of rest but balance this with some gentle exercise, such as short walks. This will give you more energy and help to keep your muscles working. Save some energy for doing the things you enjoy and ask others for help doing chores if these are tiring you out.

Skin reactions

Some people develop a skin reaction while having radiotherapy. How your skin reacts will vary depending on the amount of radiotherapy you are having. Your doctor, radiographer or nurse will tell you how to look after your skin during and after treatment.

Difficulty swallowing

After a week or two of treatment, you may find it difficult to swallow. You may also have heartburn and indigestion. This happens because the radiotherapy can cause inflammation in the tube that runs from your mouth to your stomach, called the gullet (oesophagus).

Tell your doctors if you have problems swallowing, as they can give you medicines to help. If you don’t feel like eating, or have problems with swallowing, you can replace meals with nutritious, high-calorie drinks. These are available from most chemists and can be prescribed by your GP.


You may develop a cough while you are having your radiotherapy. This usually settles within a few weeks of finishing your treatment. If it doesn’t settle, or if you develop a temperature, tell your doctor, radiographer or specialist nurse as you may have an infection.

Feeling sick

Some people find that their treatment makes them feel sick (nausea) and sometimes they may be sick (vomit).

Your doctor (or sometimes a nurse or radiographer) can prescribe effective anti-sickness drugs if this happens. Tell your doctor, nurse or radiographer if you have any nausea or vomiting.

Other information

These side effects should disappear gradually once your course of treatment is over, but it’s important to let your doctor know if they continue. We can send you more information on coping with these side effects.

Radiotherapy does not make you radioactive and it’s perfectly safe for you to be with other people, including children, throughout your treatment.

Back to Radiotherapy explained

Who might I meet?

You will meet many different specialists before, during and after radiotherapy treatment.