You have been advised to have a colonoscopy to help investigate the cause of your symptoms. It is important that you read this information before your appointment so that you have an understanding of this procedure and the preparation involved.

If you currently take medicines containing iron, you must stop taking them 7 days before your appointment. The procedure may be delayed if you have not stopped taking the iron medicine.

If you have diabetes or are taking any medication that thins your blood, other than aspirin (which you can remain on) please contact the relevant Endoscopy Unit on the Medication Advice Line (answer phone). The telephone number is at the end of this page.

If you are an insulin pump patient we would like your BM to be 7mmol/L. Please call your local pump team if you need further advice.

If you are pregnant, please seek advice from your GP or referring consultant. This is very important as your procedure may be delayed if you do not get advice.

What is a colonoscopy?

Colonoscopy is an investigation to look directly at the lining of the large bowel (colon). In order to do this, a colonoscope is passed through the anus (back passage) and into the bowel.

A colonoscope is a long flexible tube, about the thickness of your index finger; with a bright light at the end (this is not hot). By looking at the screen the doctor can see the lining of the bowel and check whether any disease is present.

For most of the time during this test you will be facing the screen. If you would like to, you will be able to view your images. It will be necessary to ask you to roll onto your back or right side at sometime during the procedure; at which point your view of the screen may be blocked.

The colonoscopy will also allow for some treatments to be performed.


A biopsy is a small sample of tissue that may be taken from the lining of your gut or bowel for further examination in the laboratory. It is taken using sterile biopsy forceps through the colonoscope. This will not be painful.


It is possible to remove polyps during a colonoscopy using a special snare. Polyps are abnormal bits of tissue, like warts, which the doctor will want to examine in more detail. This procedure is not painful.

There are other therapeutic procedures which can be done during a colonoscopy such as stretching of the bowel when there is a narrowing and argon therapy for the treatment of areas that are bleeding.

Alternative procedures

The main alternatives to colonoscopy are a barium enema

X-ray or Computed Tomography (CT) scan of the colon. These can view images of the colon but do not allow biopsies to be taken or look directly at your bowel. The alternatives will not be available on the day of your test.

Preparation for your procedure

To allow a clear view during the procedure the bowel must be cleaned using a special preparation.

You should have received your bowel preparation and full instructions on how to take it. This will also include details of what you can eat and drink before the colonoscopy.


If you have not received the preparation, or have any questions about it, please telephone the Medication Advice Line. The telephone number is at the end of this page.

Please note that you can drink clear fluids while taking the preparation right up to until your appointment time.

Clear fluids can be black tea or coffee, Bovril® or Oxo®, any squash except blackcurrant as it stains the bowel, apple juice or any other juice as long as it does not contain bits.

On admission

On arrival at the department you will be seen by a nurse who will check your personal details.

You will be asked a series of questions about any operations or illness that you may have had or are presently suffering with. Please bring a list of all medications you are currently taking.

The nurse will also ask if you have any allergies and if you have had any reactions to medicines or foods.

You will be asked if you want sedation. If you are considering sedation you will be asked to confirm that you have a responsible adult to escort you home when you are ready for discharge. You must also have a responsible adult with you at home for 24 hours following the procedure.

The test and possible complications will be explained so that you understand the procedure and any risks involved.

You will be asked to sign a consent form. By signing this form you will have agreed to have the test performed and that you understand why it is needed. This does not take away your right to have the test stopped at any time.

You will be asked to change into a hospital gown. If you are attending your appointment at Gloucestershire Royal Hospital you can bring a dressing gown and slippers with you.

Please remember that your appointment time is not the time you will have your colonoscopy. There will be a waiting time between your admission and having your test done.

For the time that you are in the department we want to provide a safe, supportive and pleasant environment so please do not be afraid to ask if you have any worries or questions at this stage.

The colonoscopy

The test and possible complications will be explained to you so that you understand the procedure and any risks.

A nurse or doctor will escort you into the room where your colonoscopy will take place. A nurse will stay with you throughout the test.

You will be made comfortable on a couch lying on your left side, with your knees slightly bent.

A rectal examination may be done as part of the procedure. This is where a doctor uses their finger to check for any problems inside your bottom (rectum). This is usually very quick and you should not feel any pain.

A colonoscopy normally takes about 20 to 40 minutes.

Intravenous sedation

The sedation will be given into a vein in your hand or arm. This will make you lightly drowsy and relaxed but not unconscious. You will be in a state called conscious sedation. This means that, although drowsy, you will still hear what is said to you and therefore will be able to follow simple instructions during the investigation. Sedation also makes it unlikely that you will remember anything about the procedure. You will be able to breathe normally during the procedure.

While you are sedated we will check your breathing and heart rate so any changes will be recorded and dealt with accordingly.

For this reason you will be connected by a finger probe to a pulse oximeter which measures your oxygen levels and heart rate during the procedure. Your blood pressure will also be recorded.

Please note that if you decide to have sedation you should not drive, drink alcohol, operate heavy machinery or sign any legally binding documents for 24 hours following the procedure. You will need someone to accompany you home and a responsible person to stay with you for 24 hours.

If suitable, Entonox® (gas and air) is also available during the procedure either as an alternative to sedation or as well as sedation. This will help to control any discomfort.

You will not need a responsible adult to stay with you if you choose Entonox® only. A leaflet can be provided.

If you have experienced or suffered with any of the following within the last 12 weeks, Entonox® will not be suitable for you.

  • Pneumothorax
  • Air embolism
  • Emphysema/COPD
  • Recent ear/eye surgery
  • Head injury with impaired consciousness
  • Bowel obstruction
  • Scuba diving
  • Decompression sickness

Risks associated with having sedation

Sedation can sometimes cause problems with breathing, heart rate and blood pressure. If any of these problems happen, they are normally short lived.

Careful monitoring by a fully trained endoscopy nurse makes sure that any problems are identified and treated rapidly.

Older patients and those who have health problems, for example, people with breathing difficulties due to a bad chest will be assessed by a doctor before the procedure.


Complications are uncommon with diagnostic (investigative) procedures and are mostly due to the sedation given. Major complications are very rare.

If a biopsy is taken or a polyp removed it can lead to bleeding or a perforation (a tear) of the bowel. It might be necessary to admit you to hospital for treatment. This happens in less than 1 in every 5,000 cases and rarely blood transfusions and/or surgery is needed. If surgery is needed it will be a major operation but the risks of complications are small.

The overall chance of missing something important, such as a cancer, is less than 1 in 2,500.

After the test

After the colonoscopy is completed the nurse caring for you during your test will take you from the endoscopy room to the recovery area.

Your pulse and blood pressure will be monitored as needed. This is called the recovery period. You may feel a little bloated or have some discomfort in your lower abdomen after the test.

This is normal and it should start to ease by the time you are discharged.

You will need to stay in hospital for about 1 hour after the procedure depending on how you recover from the sedation given.

Normally you do not see the person who performed your procedure before going home. Your nurse will tell you the results of the test before discharge. If you have had sedation it is a good idea to have someone with you at this discussion as many people find they forget what has been said to them. You will be given written information to take home.

If a sample (biopsy) has been taken, the result will take up to

5 weeks to process. You may be given an outpatient’s appointment to return for review or alternatively the results will be forwarded to your GP. In this case you will need to make an appointment to see him/her.

Going home

If you have had sedation it is essential that someone takes you home and that there is a responsible adult to stay with you for 24 hours.

You may go home by taxi or public transport but you must have someone to accompany you on the journey.

For this period of time, you should not:

  • Drive a car, motorbike or ride a bicycle.
  • Drink alcohol.
  • Operate machinery or do anything requiring skill or judgment.
  • Make important decisions or sign any documents.

If you did not have sedation the above paragraph does not apply.

If you have received Entonox® for pain relief you will need to stay in the department for 30 minutes before going home.

An advice sheet including this information will be given to you before you leave; this is your discharge letter. You will be given a procedure report. A copy of the report will also be sent to your GP.

If you have a polypectomy (polyp removed from your bowel), there is a risk of delayed bleeding. If the polyp is large or there are lots to be taken away it is important to let your endoscopist know if you intend to travel (especially long haul flights) in the days following this treatment.

Gloucestershire Hospitals NHS Foundation Trust is an Endoscopy Training Centre. We regularly have registrars and nurse endoscopists working on the unit. Please discuss any concerns or issues you may have with the admission nurse.

Contact information

Appointment Enquiries

Tel: 0300 422 6350

Tel: 0300 422 6351

Monday to Sunday, 8:30am to 4:00pm

Medication Advice Line (answer machine)

If you have any questions relating to your medication, please leave a message. A member of staff will return your call normally within 24 hours, Monday to Friday only.

Cheltenham General Hospital

Tel: 0300 422 3370

Monday to Friday, 8:00am to 6:00pm

Gloucestershire Royal Hospital

Tel: 0300 422 8232

Monday to Friday, 8:00am to 6:00pm

Saturday and Sunday, 9:00am to12:00 midday

Other Endoscopy Units

Cirencester Hospital

Tel: 0300 421 6294

Monday to Friday, 8:00am to 6:00pm

Stroud General Hospital

Tel: 0300 421 8073

Monday to Friday, 8:00am to 6:00pm

Printable version of this page

Having a colonoscopy as an outpatient GHPI1077_02_23 Department: Endoscopy Review due: February 2026 PDF, 310.0 KB, 8 pages
Reference number GHPI1077_02_23
Department Endoscopy
Review due February 2026