Overview

A colonoscopy is a test to help find what is causing your bowel symptoms.

A specially trained doctor or clinical endoscopist puts a soft, flexible tube with a camera at the end through your bottom (anus). This tube then passes up inside your bowel.

You can find more information about having a colonoscopy on the NHS website.

This information explains what you need to do in the days before your colonoscopy. Please read the guidance carefully at least 5 days before your appointment. It tells you:

• what you need to eat and drink
• how to take bowel preparation solution
• what medicines you need to stop taking

It's important that your bowel is completely empty for the colonoscopy. We can then see the lining of the bowel clearly. Diet and a bowel preparation solution help to make sure that your bowel is empty. If you do not follow this guidance, your bowel may not be clear and we may have to cancel and rebook your procedure. 

It’s particularly important to follow our guidance if you take medicines. 

Medicines

You'll be contacted by the pre-assessment team 1 to 2 weeks before your colonoscopy. During this appointment, they'll discuss your current medicines and tell you which medicines you might need to stop taking before your procedure. 

Please tell us if you are taking: 

• medicines to thin your blood or prevent it from clotting (anticoagulants or antiplatelets), such as aspirin, warfarin, dabigatran, rivaroxaban or clopidogrel
• any sedatives or medicines for chronic pain 
• any medicines for diabetes 
• weight loss injections, as such as Wegovy® (semaglutide), Mounjaro® (tirzepatide) or Saxenda® (liraglutide)

You should also tell us if you are taking any other medicines, such as:

• anything you buy from a pharmacy or shop
• herbal or homeopathic medicines 

Let us know if you have a device for your heart, such as a pacemaker or implantable cardioverter defibrillator (ICD). 

Food and drink

You'll need to make some changes to your diet before your procedure.

Please make sure you follow the instructions listed in each section of this guide. 

Bowel preparation

You need to take a bowel preparation solution. This helps you poo and empties your bowel. 

You'll need to take it: 

• 1 day before your colonoscopy
• on the day of your colonoscopy

You’ll need to collect the solution at least 3 days before your colonoscopy. You can collect it from the endoscopy reception at St Thomas' hospital, Monday to Sunday 9am to 5pm. 

Bowel preparation solutions

We prescribe you one of these solutions:

• CitraFleet® or Picolax® (sodium picosulphate) with senna tablets 
• Moviprep®
• Plenvu® 

The nurse will assess which one is most suitable at your pre-assessment appointment.

You might need to have a blood test before and after the procedure to check how your kidneys are working. Please tell us if: 

• you cannot drink a large amount of fluid 
• the amount of fluid that you can drink each day is restricted
• a doctor has told you that your kidneys are not working properly.

If we are concerned about your kidneys or you have kidney problems, we will prescribe you Moviprep or Plenvu.

Senna tablets

We prescribe senna tablets with CitraFleet® or Picolax®. Senna is a natural laxative and is used to treat occasional constipation (difficulty pooing). 

To use senna tablets safely:

• keep them out of children's reach and sight
• store them in the original container
• check that the foil is not broken before use. If it is, do not take that tablet
• do not take them if you know that you are allergic to any of the ingredients
• do not store them above 25C
• do not freeze them
• do not use them after the expiry date

You may get mild stomach pains for a short time. If the pain becomes bad or you have other symptoms after taking the tablets, tell your doctor or pharmacist.

Going to the toilet

You need to stay near a toilet when you start taking the bowel preparation solution.

You can expect to poo frequently and have diarrhoea (watery poo). This starts within 3 hours of taking the first amount (dose) and continues until after your last dose.

We plan when you take the bowel preparation solution carefully. This means that the effects wear off before you are due to travel to the hospital.

Side effects of bowel preparation

It's common to have some bloating (when your tummy feels full and uncomfortable) or stomach cramps.

You can use a barrier cream (a cream to protect the skin from damage or infection), such as zinc and castor oil, on your bottom. This can prevent soreness during your frequent trips to the toilet.

Keep drinking clear fluids to stop yourself from getting dehydrated. As a guide, try to drink about 1 glass every hour. Signs that you are dehydrated include dizziness, headache and confusion.

Please report any allergic reactions, such as a rash, itchiness or redness, to the endoscopy unit or your GP.

If you take the contraceptive pill

If you take the contraceptive pill, it may not work when you have taken the bowel preparation solution. Use another type of contraception (such as condoms) to avoid getting pregnant. Please speak to your GP, pharmacist or family planning clinic for more advice on contraception.

If your health gets worse

If your health has got worse since last seeing the doctor or specialist nurse in the clinic, please call the endoscopy nurses for advice on 020 7188 7188. Ask for extension 54059 (St Thomas’ Hospital) or extension 53499 (Guy’s Hospital).