Radiotherapy

Long term side effects of radiotherapy

Most radiotherapy side effects gradually go away in the weeks or months after treatment. But some side effects can continue. Or you might notice some that begin months or years later. Most are rare.

Tiredness and weakness

Tiredness after radiotherapy might carry on for some months. You might also feel weak and lack energy. Various things can help you to reduce tiredness and cope with it, for example exercise.

Some research has shown that taking gentle exercise can give you more energy. It is important to balance exercise with resting.

Get tips on coping with tiredness

Blood in your urine

You may see blood when you pass urine. This can happen because the radiotherapy has irritated your bladder and made the blood vessels weak.

The bleeding can vary from only a small amount to lots. Do tell your doctor or nurse straight away if you have blood in your urine.

Seeing blood in your urine can be very worrying for you, as you may think your cancer is back. You can have a check up to find out that this is not a sign it's come back.

Passing urine more often

You might feel as if you want to pass urine all the time. This can happen because your bladder may shrink slightly after radiotherapy. This is an uncommon side effect.

Just can’t wait card

You can get a card to show to staff in shops or pubs etc. It allows you to use their toilets, without them asking awkward questions. You can get the cards from Disability Rights UK or the Bladder and Bowel Foundation. They also have a map of all the public toilets in the UK.

You could get a key to disabled toilets if you need to access them quickly. You buy the RADAR key from Disability Rights UK.

Damage to your bowel

Long term bowel damage is rare. Some of the long term side effects on your bowel could include:

urgency to poo
being unable to control when you poo (incontinent)

Tell your doctor or nurse if your bowels are troubling you. They may be able to help give you something to reduce the symptoms.

Weaker bones and crack in bones

Having pelvic radiotherapy can cause your bones to become weaker, this can make you more prone to them breaking (fracturing). This usually might develop after you’ve finished your radiotherapy treatment.

Your doctor might give you a medicine to strengthen your bones called . These drugs can help to control pain and reduce the risk of fractures. If they think you have fractured your bone you may have an , or to check this. You might have a combination of these scans.

Let your team know of any pain you may have.

Find out more about bisphosphonates

Low levels of vitamin B12

You might have low after radiotherapy to the pelvis (the area between your hip bones). This is called a vitamin B12 deficiency.

Radiotherapy can stop your from taking in (absorbing) vitamin B12 from the food you eat. This is called malabsorption. This means you can have a B12 deficiency even if you eat a balanced diet.

A B12 deficiency can be a cause of . This can lead to weakness, diarrhoea, numbness and tingling.

It’s important that you go to your doctor if you’re experiencing these symptoms so that they can help you.

Changes to your sex life

You can have some changes that can affect your sex life. These changes may continue some time after treatment.

Men can experience a lower sex drive, difficulty getting an or problems with .

Women may have dryness and shrinkage of the , making sex painful. Some women also experience an early .

Both men and women might lose their .

Talk to your doctor if you think you have developed any of these side effects.

Side effects of chemoradiotherapy

Having chemotherapy combined with radiotherapy (chemoradiotherapy) can make some side effects worse.

Last reviewed: 21 Aug 2025

Next review due: 21 Aug 2028

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Bladder cancer main page

Bladder cancer is cancer that starts in the lining of the bladder. The bladder is part of the urinary system, which filters waste products out of your blood and makes urine. Find out about the symptoms, how you are diagnosed, treatment, living with bladder cancer and follow up.