Why Diet Matters
This page has been designed to provide dietary advice for patients preparing for a colonoscopy, which is important to ensure clear and accurate results. To get clear results, your bowel needs to be completely clean. Some foods (like those high in fibre, seeds, or skins) leave residue in the bowel and must be avoided before your procedure.
We understand that following a vegetarian or vegan diet is an important part of your lifestyle and values. This page offers specific guidance on how to prepare for your procedure while respecting your dietary choices. Please ask if there is anything you do not understand it or if you have any questions.
Choose low-fibre foods and avoid anything that is wholegrain, seedy, or fibrous.
Foods you can eat (vegan/vegetarian options):
- White bread, white rice, plain pasta, noodles
- Tofu, seitan, smooth nut butters (in small amounts, without seeds)
- Plain potatoes (peeled, not with skin)
- Low-fibre cereals (cornflakes, Rice Krispies)
- Well-cooked peeled vegetables (e.g., carrots, pumpkin, zucchini without skin or seeds)
- Ripe bananas, canned peaches/pears (without skin), applesauce
- Dairy alternatives (soy milk, oat milk, almond milk, coconut yoghurt)
- Clear soups/broths made with vegetable stock (strained, no bits)
Foods to Avoid:
- Whole grains, brown rice, granola, oats
- Beans, lentils, chickpeas, peas, corn
- Raw vegetables, salads
- Skins, pips, seeds, nuts, popcorn
- Fruits with skins, berries, dried fruit
The day before your procedure you will usually be asked to have a clear liquid diet only (no solid food until after your procedure).
Allowed clear liquids (vegan-friendly):
- Water
- Clear fruit juices without pulp (apple juice, white grape juice)
- Clear vegetable broth (strained, no solids)
- Herbal teas (no fruit bits or seeds)
- Black tea or black coffee (no milk, cream, or non-dairy creamers with solids)
- Clear sports drinks, electrolyte drinks
- Ice lollies or jelly (avoid red, blue, or purple colours, as they can stain the bowel)
Liquids to Avoid:
- Solid foods of any kind
- Smoothies, milk, or plant milks
- Juices with pulp
- Thick soups
Please drink all the bowel preparation and at least 500 ml of fluids. You can continue to drink up to two hours before appointment time. If you are having a Gastroscopy (OGD) procedure performed during the same appointment as your colonoscopy you will need to stop drinking four hours prior to your procedure.
On the day of your test, please bring a list of all the medications you are currently taking.
If you are taking any blood thinning medications such as warfarin, clopidogrel, rivaroxaban, apixaban or any others, you should receive specific instructions on what to do prior to your appointment regarding these medications.
If you have not received this information, or if you have any questions, please contact Endoscopy Recovery on 020 3447 3282.
If you are diabetic and take insulin, it is important that you continue taking your insulin. We will advise you how much to reduce your insulin when you are seen in clinic before your procedure. If you take diabetic tablets, please do not take these from the moment you start fasting (day prior to your procedure). Please do not restart this medication until after the procedure has been done.
If you are pregnant, or think you may be pregnant, you should not undergo this procedure. If you are of childbearing age, you will need to take a urine test to see if you are pregnant before you can have this procedure.
When you arrive at the Endoscopy Unit please report to the reception. From there a nurse will take you to admissions, check your personal details, check your blood pressure and you will be asked to change into a hospital gown. When it is time for your procedure, the endoscopist will come to meet you in your admissions bay and you be asked to sign a consent form.
We want to involve you in all the decisions about your care and treatment. If you decide to go ahead with treatment, by law we must ask for your consent and will ask you to sign a consent form. This confirms that you agree to have the procedure and understand what it involves. Staff may explain the risks, benefits and alternatives before the endoscopist comes to visit you in the room, but this will be fully explained by the endoscopist in detail as part of the consenting process. If you are unsure about any aspect of your proposed treatment, please ask the endoscopist or anaesthetist.
From there, we will take you into one of the endoscopy rooms. You will be able to take your belongings with you or they may be left with friends or relatives. Friends and relatives can wait in the waiting room.
The anesthetist will administer the sedation or anaesthetic via a small needle in the back of your hand. Drugs usually take a few minutes to make you feel relaxed and drowsy. In cases where a general anaesthetic is administered this will make you go to sleep. Your vital signs will be constantly monitored during the procedure, and you may also be given a small amount of oxygen during the procedure.
Before the procedure starts you will be asked to lie on a trolley. You will have some equipment attached to you so that we can monitor your blood pressure and oxygen levels. You will be given a small amount of oxygen during the procedure.
You will be asked to lie on your left side. However, you may be asked to change your position during the colonoscopy. If you are being sedated the endoscopist will administer the medication via a small needle in the back of your hand at this time. Sedation may take a few minutes to work.
After you have had your procedure, you will be taken to the recovery area. You will be kept there for approximately one hour so the effects of the sedation can wear off. Your blood pressure and oxygen levels will be monitored during this time.
When you are fully awake, the endoscopist will come to explain the results of your procedure. You will then be able to go home or be transferred to a ward depending on prior arrangements for an overnight stay.
When you are well enough to be discharged, you will receive an information sheet giving advice on aftercare and details of who to contact if you have any problems. A plan will also be made to see you again in clinic to discuss the results of the procedure.
Do read section seven regarding medicines.
Do ask for an interpreter if you require one, as hospital policy states that family or friends cannot interpret on behalf of the patient.
Do not drink any form milk 24 hours before your colonoscopy procedure.
Do not bring large sums of money or valuables to the hospital as we cannot accept responsibility for loss or damage.
Pathway Co-Ordinator (Monday to Friday 09:00-17:00)
Direct line: 0203 447 7488
Switchboard: 08451 555 000 / 020 3456 7890 ext. 71488
E-mail: uclh.
Endoscopy Recovery (Monday to Friday 09:00-17:00)
Direct line: 020 3447 3282
Switchboard: 08451 555 000 / 020 3456 7890 ext. 73282
Address: Endoscopy Unit, University College Hospital, 2nd Floor Podium, 235 Euston Road, London, NW1 2BU
Services
Page last updated: 12 November 2025
Review due: 31 October 2027