What is a colonoscopy?

  • A colonoscopy is a test to check inside your bowels.
  • This test can help find what's causing your bowel symptoms.
  • A long, thin, felxible tube with a small camera iside it is passed into your bottom.
  • You'll be given a laxative so your bowels are empty for the test.


You're usually awake during a colonoscopy.  You'll be offered medicine to make you more comfortable and make the test easier.

Why should it be done?

Why it's done

A colonoscopy can be done to look for a number of things.

To check the cause of your bowel symptoms

A colonoscopy is often due to check what's causing your bowel symptoms, such as:

  • bleeding from your bottom or blood in your poo
  • diarrhoea or constipation that does not go away
  • losing weight or feeling really tired for no reason

Most of the time it will not find anything to worry about.

But sometimes it might find something that needs a closer look or further testing.

To check for growths in your bowels (polyps)

Lots of people have growths in their bowels (bowel polyps), and most of the time they're harmless.  But they can sometimes become cancer, so if they're found they need to be checked.

They can be removed during the colonoscopy and then tested.

Your results will tell you if you need any futher tests or treatment.

To look for signs of bowel conditions

A colonoscopy can be used to look for bowel conditions like:

These conditions can be hard to diagnose, so you may also have other tests.





Getting Ready

Getting your letter

Once you've been referred you'll get a letter, in the post or by email, telling you when your colonoscopy will be.

Some hospitals will phone you to book you in, but you should also get a letter - call the hospital if you do not get one.

Your letter will:

  • tell you what you need to eat and drink in the days before your test
  • tell you when you should stop eating and drinking
  • have laxatives with it for you to take before the test, or information on how to get them
  • tell you how to take the laxatives


If you're pregnant, or taking any medicines, let the hospital know as soon as you get your letter.

Getting ready for a colonoscopy

2 days before

For 2 days before a colonoscopy, you should only eat plain foods like:

  • plain chicken not in a sauce
  • white rice, pasta or bread
  • clear soup

Your letter should tell you what you can eat and drink.

1 day before

The day before your colonoscopy you'll need to drink sachets of laxatives to empty your bowels ready for the test.

Most people:

  • need to drink a few sachets
  • need to drink the sachets at different points throughout the day
  • get diarrhoea a few hours after taking the first sachet

Stay at home and be near a toilet after you've started drinking the laxatives.


You need to drink the laxative as it says on your letter. Otherwise ther specialist may not be able to do your colonoscopy.

What happens?

On the day of your colonoscopy you'll need to stop eating and drinking - your letter will tell you when to stop.

You should also bring any medicines you take with you.

When you arrive

You'll speak with a nurse about what's going to happen. They will ask you to change into a hospital gown.

You may be offered things to make you more comfortable and make the test easier, such as:

  • painkillers
  • sedation - medicine given through a small tube in your arm to help you relax
  • gas and air - you breathe this in to help you relax

Not all hospitals offer all these things - ask about what you can have.


You cannot drive for 24 hours if you have sedation. Someone will need to pick you up from hospital in a car or taxi.

Giving consent

A nurse or specialist will explain possible risks.

In rare cases, people may:

  • have a reaction to the sedation
  • have some bleeding afterwards
  • get a small tear in their bowels

You'll be asked to sign a consent form. This is to confirm you understand the risks and agree to have the procedure.

It's important to remember these things are rare. If anything happens, the team will take care of you.

The procedure

It should take 30 to 45 minutes to have your colonoscopy.

But you might be at the hospital for around 2 hours from getting there to going home.

What happens - A thin, flexible tube with a small camera inside goes into your bottom
What it might feel like - You may feel the camera go in, but it should not hurt

What happens - Air is pumped in to open up your bowels
What it might feel like - You may feel a bit bloated or like you need the toilet

What happens - The tube goes through all of your large bowel
What it might feel like - You may have some stomach cramps

What happens - Any growths (polyps) in your bowels will be removed or a sample of cells taken
What it might feel like - You will not feel anything if this happens

You'll usually be told if any growths (polyps) have been removed.

You'll then be moved to the recovery room. The nurse will monitor you until you're ready to go home.

How you might feel after a colonoscopy

You might feel bloated or have stomach cramps for 2 to 3 hours after.

You may also have some blood in your poo or bleeding from your bottom. These things are common.

Call NHS 111 Wales, or the hospital where you had a colonoscopy, if:

You have any of these things after having a colonoscopy:

  • heavy bleeding from your bottom or bleeding that's getting worse
  • severe stomach pain or pain that gets worse
  • a high temperature or you feel hot or shivery

What we mean by severe pain

Severe pain:

  • always there and so bad it's hard to think or talk
  • you cannot sleep
  • it's very hard to move, get out of bed, go to the bathroom, wash or dress

Moderate pain:

  • always there
  • makes it hard to concentrate or sleep
  • you can manage to get up, wash or dress

Mild pain:

  • comes and goes
  • is annoying but does not stop you doing daily activities


You should get a letter or a call with your results 2 to 3 weeks after a colonoscopy.

If your GP sent you for the test, they should also get a copy of your results. Call the hospital if you have not heard anything after 3 weeks.

Normal results

This means no growths (polyps) or cancer have been found in your bowel.

If you're at higher risk of bowel problems, you might be asked to have regular colonoscopies every few years to check everything is still okay.

Growths (polyps)

Your results may show they found and removed growths (polyps).

Your results will also say if, after testing the growths, they think you need any further treatment.

Or they may just say you need to come back in the future for a check-up colonoscopy.

Bowel cancer

If your results say you have cancer, you'll see a cancer specialist for treatment as soon as possible.

The earlier anything is found, the easier and the quicker it can be treated.

A bowel condition that's not cancer

A colonoscopy can help to confirm if you have a bowel condition that's not bowel cancer.

This could be:

If you have one of these conditions you may need more treatment.

Speak to a GP to find out the next steps.

Support is available

Most of the time a colonoscopy will not find anything to worry about.

But it might help to speak to someone if you're feeling worried about your results.

You can get in touch with charities such as:


The information on this page has been adapted by NHS Wales from original content supplied by NHS UK NHS website
Last Updated: 21/05/2024 10:30:53