The procedure you will be having is called a colonoscopy.

This is an examination of your large bowel (colon). It will be performed by or under the supervision of a trained endoscopist and we will make the investigation as comfortable as possible for you. When you are having a colonoscopy procedure you will usually be offered sedation and analgesia.

Why do I need to have a colonoscopy?

  • You may have been advised to undergo this investigation of your large bowel to try and find the cause for your symptoms, help with treatment, and if necessary, to decide on further investigation.
  • Follow-up inspection of previous disease.
  • Assessing the clinical importance of an abnormality seen on an x-ray or scan.
  • A CT Colonogram examination is an alternative investigation to colonoscopy. It has the disadvantage that samples of the bowel cannot be taken if an abnormality is found. If this is the case a subsequent endoscopic examination may be required.

What is a colonoscopy?

This test is a very accurate way of looking at the lining of your large bowel (colon), to establish whether there is any disease present. This test also allows us to take tissue samples (biopsy) for analysis by the pathology department if necessary.

The instrument used in this investigation is called a colonoscope, (scope) and is flexible. Within each scope is an illumination channel which enables light to be directed onto the lining of your bowel, and another which relays pictures back, onto a television screen. This enables the endoscopist to have a clear view and to check whether or not disease or inflammation is present.

During the investigation the endoscopist may need to take some samples from the lining of your colon for analysis: this is painless. The samples will be retained. A video recording and/or photographs may be taken for your hospital records.

Preparing for the investigation

Eating and drinking: It is necessary to have clear views of the lower bowel.

Three days before your appointment

  • You will need to be on a low fibre diet and considerably increase your fluid intake. A diet sheet is included with the laxative sent to you.

One day before

  • In addition you will need to take a laxative which should have arrived with this booklet along with clear instructions on how to administer it. If you have any queries do not hesitate to contact the endoscopy unit and someone will assist you.

On the day of the examination

  • You may continue taking clear fluids until you attend for your appointment.

What about my medication?

Usually your routine medication should be taken.

If you are taking iron tablets you must stop these one week prior to your appointment. If you are taking stool bulking agents (e.g. Fybogel, Regulan, Proctofibe), Loperamide (Imodium) Lomotil or Codeine Phosphate you must stop these two days prior to your appointment. You may be asked to stop your diuretic or hypertensive (blood pressure medication) on the day you take bowel prep and the day of the procedure.


If you are diabetic controlled on insulin or medication, please call the Endoscopy department so that the appointment can be made at the beginning of the list.

Please see guidelines printed at the back of the book.


Please telephone the unit if you are taking blood-thinning medication such as warfarin, clopidogrel (Plavix), Rivaroxaban, Apixaban or Dabigatran. Please bring a copy of your prescription.

How long will I be in the endoscopy department?

This largely depends on how busy the department is. You should expect to be in the department for for the whole morning and afternoon depending on your appointment time. We suggest you bring a book or a magazine.

The department also looks after emergencies and these can take priority over our outpatient lists.

What happens when I arrive?

When you arrive in the department, you will be met by a qualified nurse or health care assistant who will ask you a few questions, one of which concerns your arrangements for getting home. You will also be able to ask further questions about the investigation.

The nurse will ensure you understand the procedure and discuss any outstanding concerns or questions you may have. As you will be having sedation a small cannula maybe inserted (small plastic tube) in the back of your hand through which sedation will be administered later.

As you will have sedation you will not be permitted to drive or use public transport so you must arrange for a family member or friend to collect you. The nurse will need to be given their telephone number so that we can contact them when you are ready for discharge.

You will have a brief medical assessment when a qualified endoscopy nurse will ask you some questions regarding your medical condition and any surgery or illnesses you have had to confirm that you are fit to undergo the investigation.

Your blood pressure and heart rate will be recorded and if you are diabetic, your blood glucose level will also be recorded. Should you suffer from breathing problems a recording of your oxygen levels will be taken.

If you are happy to proceed, you will be asked to sign your consent form at this point.

Intravenous sedation

Please note as you have had sedation, you must not drive, take alcohol, operate heavy machinery or sign any legally binding documents for 24 hours following the procedure and you will need someone to accompany you home. We recommend someone responsible stays with you overnight after the procedure.

The colonoscopy investigation

In turn you will be escorted into the procedure room where the endoscopist and the nurses will introduce themselves and you will have the opportunity to ask any final questions.

The nurse looking after you will ask you to lie on your left side and will then place the oxygen monitoring probe on your finger.

The sedative drugs will be administered into a cannula (tube) in your vein.

The colonoscopy involves manoeuvring the colonoscope around the entire length of your large bowel. There are some bends that naturally occur in the bowel and negotiating these may be uncomfortable for a short period of time but the sedation and analgesia will minimise any discomfort.

CO2 or Air is gently passed into the bowel during the investigation to facilitate the passage of the colonoscope.

During the procedure samples may be taken from the lining of your bowel for analysis in our laboratories. These will be retained.

Risks of the procedure

Lower gastrointestinal endoscopy is classified as an invasive investigation and because of that it has the possibility of associated complications. These occur extremely infrequently; we would wish to draw your attention to them and so with this information you can make your decision.

The doctor who has requested the test will have considered this. The risks must be compared to the benefit of having the procedure carried out.

The risks can be associated with the procedure itself and with administration of the sedation.

The endoscopic procedure

The main risks are of mechanical damage;

  • Perforation (or tear in the bowel wall) risk approximately 1 for every 1,000. An operation is nearly always required to repair the hole. The risk of perforation is higher with polyp removal.
  • Bleeding may occur at the site of biopsy or polyp removal (risk approximately 1 for every 100-200 examinations where this is performed). Typically minor in degree, such bleeding may either simply stop on its own or if it does not, be controlled by cauterization or injection treatment.
  • Pain - usually this procedure is well tolerated. It is common to experience short lived discomfort, however, a small percentage of patients may experience pain with this procedure.


Sedation can occasionally cause problems with breathing, heart rate and blood pressure. If any of these problems do occur, they are normally short lived. Careful monitoring by a fully trained endoscopy nurse ensures that any potential problems can be identified and treated rapidly.

Older patients (over 75 years) and those of all ages with medical conditions will be offered an alternative investigation.

Mostly this would be a virtual colonoscopy in a CT scan.

What is a polyp?

A polyp is a protrusion from the lining of the bowel. Some polyps are attached to the intestinal wall by a stalk, and look like a mushroom, whereas others are flat without a stalk. Polyps when found are generally removed or sampled by the endoscopist as they may grow and later cause problems. Flat polyps are generally a little more difficult to remove.

A polyp may be removed in several ways, which can include using an electrical current known as diathermy.

After the procedure

You will be moved to our recovery area where your blood pressure and heart rate will be recorded and if you are diabetic, your blood glucose will be monitored. Should you have underlying breathing difficulties or if your oxygen levels were low during the procedure, we will continue to monitor your breathing. Once you have recovered from the initial effects of the sedation (which can take up to 60 minutes) you will be moved to a seated area and offered a hot drink and biscuits. Before you leave the department, the nurse or endoscopist will discuss the findings, give you a short written report (discharge letter) and any medication or further investigations required. They will also inform you if you require further appointments.

Because you have had sedation, the drug remains in your blood system for about 24 hours and you may feel drowsy later on, with intermittent lapses of memory. If you live alone, try and arrange for someone to stay with you or, if possible, arrange to stay with your family or a friend for at least 4 hours.

If the person collecting you leaves the department, the nursing staff will telephone them when you are ready for discharge.

General points to remember

  • The time on your appointment letter is your arrival time and not the time of your test as some preparation is required before the procedure.
  • The hospital cannot accept any responsibility for the loss or damage to personal property during your time on these premises.
  • If you are unable to keep your appointment please notify the endoscopy department as soon as possible.
  • Because you are having sedation, please arrange for someone to collect you.
  • If you have any problems with persistent abdominal pain or bleeding please leave a message on the Endoscopy Helpline for advice. Contact details will be on your discharge letter, which you will receive after the procedure.

Advice for people with Diabetes

Inform the endoscopy department that you have diabetes so the appointment can be arranged where possible for the beginning of the list.

It may be necessary to modify normal diabetic treatment so that fasting can be tolerated. This may result in erratic blood sugar levels for a short period but diabetic control should return to normal with 1-2 days.

Remember to monitor blood glucose levels four hourly if you are on insulin (bring your meter with you). If your blood glucose level falls below 4mmol/L inform a member of staff in the Endoscopy Unit. Take 4-5 glucose tablets or 150mls of a glucose drink e.g. glucojuice if you have these with you and ensure you re-check after 10 minutes. Your blood sugar will be checked on arrival to the unit.

Preparation before the procedure

As advised earlier in this booklet there are two days of preparation before the examination. When following the low fibre diet on the first day try to make sure you eat your usual amounts of carbohydrate from the allowed list eg white bread, white rice, pasta etc. Continue to take your usual tablets and/or insulin and check your blood sugar levels as usual.

Day before the colonoscopy

CLEAR FLUIDS ONLY. Aim to have carbohydrate at your usual meal times from the list of permitted clear fluids. You can have sugary fluids, fruit juice or fruit jelly to replace your usual carbohydrates.

Diabetes treated with tablets

  • Take tablets as normal on the morning of the day before the procedure. After this, omit all diabetes tablets and only restart at lunchtime after the test.

Diabetes treated with insulin

For four injections per day e.g. short acting with meals and long acting once/day

  • Half the normal dose of short acting insulin

  • No change is required to the basal insulin

For twice daily long acting or intermediate acting insulin

  • No dose change is required

For twice daily mixed insulin e.g. Humulin M3, Humalog Mix 25, Humalog Mix 50, Novomix 30, Insuman Comb 15, Insuman Comb 25, Insuman Comb 50

  • Take half of the normal insulin morning and evening

For once daily insulin e.g. Lantus (Glargine), Abasaglar, Levermir (Determir), Tresiba (Degludec), Toujeo, Insuman Basal, Insulatard or Humulin I

  • No dose change is required

Day of the colonoscopy

Diabetes treated with tablets

Do not take your diabetes tablets on the day of the test. Take your next dose of tablets when you are allowed to eat again.
If your diabetes is treated with a combination of insulin and tablets, follow the advice for tablets as before and insulin as outlined below.

Diabetes treated with GLP-1 injections

If your diabetes is treated with GLP-1 injections e.g. (Exenetide (Byetta), Liraglutide (Victoza), Lixisenatide (Lyxumia) or Dulaglutide (Trulicity)

  • Omit on the day of the procedure
  • Resume once you are eating normally again

Be aware that blood sugar levels may be disturbed by the change in routine but should return to normal within 24-48 hours.

Diabetes treated with insulin

For once daily insulin e.g. Lantus (Glargine), Abasaglar, Levermir (Determir), Tresiba (Degludec), Toujeo, Insuman Basal, Insulatard or Humulin I

  • If your procedure is in the morning, no dose change is required.
  • If your procedure is in the afternoon, take half of your usual insulin dose. Take the normal dose the following morning after your test.

For twice daily long acting or intermediate acting take two-thirds of your normal dose in the morning.

  • If your procedure is in the morning, no dose change is required.
  • If your procedure is in the afternoon, take half of your usual insulin dose.

For twice daily mixed insulin e.g. Humulin M3, Humalog Mix 25, Humalog Mix 50, Novomix 30, Insuman Comb 15, Insuman Comb 25, Insuman Comb 50

  • Take half of the normal dose in the morning whether you are on the morning or afternoon list. Resume your normal insulin regime with your next meal.

For four or more injections a day

  • No dose change is required for the basal insulin.
  • Omit the quick acting insulin (Novorapid, Humalog, Apidra, Humalog U200, Humulin S, Actrapid or Fiasp) at breakfast if you are having the procedure in the morning. If the procedure is in the afternoon, omit the breakfast and lunchtime doses.

For people with Type 1 diabetes on pump therapy, discuss with a member of the diabetes team.

If you have any concerns about adjusting your dosage please contact the Diabetes Nursing Team well in advance of the appointment, to discuss appropriate measures.

If you or the individual you are caring for need support reading this leaflet please ask a member of staff for advice.

How to contact us:

0117 414 5040

© North Bristol NHS Trust. This edition published May 2021. Review due May 2023. NBT002231