A gastroscopy is a procedure which allows us to look directly at the upper part of your digestive system – the oesophagus (or food pipe), stomach and duodenum (the first part of the small bowel). The test is sometimes called an endoscopy or an OGD (oesophago-gastro-duodenoscopy). The endoscopist passes a thin, flexible tube with a very small camera at the end (called a gastroscope or endoscope) through your mouth and into your stomach. The procedure takes about five to ten minutes. The endoscopist may take small tissue samples.
Gastroscopy is a test which helps your doctor find the cause of symptoms including:
- Indigestion
- Heartburn
- Losing weight without trying
- Being sick (vomiting)
- Anaemia
- Difficulty swallowing
- A lump in the throat
- Regurgitation
There is the option to have the endoscopy undertaken with throat spray only. If that is the case it is not required for you to bring an escort. You will be able to leave alone. In the majority of cases however, the procedure is undertaken with sedation, particularly if you are having some form of treatment or if the procedure is going to be prolonged. This medication allows you to relax. This is not the same as a general anaesthetic, but in the majority of cases, this works very well to allow for the procedure to be performed and completed quickly, efficiently and safely. These medications include Midazolam (a sedative) and Fentanyl (a pain killer).
There is a possibility that the endoscopist might choose to give you the sedative on top of the throat spray, a decision will be made by the endoscopist on the day. Please inform us if you have any particular preferences or intolerances to these medications. Crucially, sedation cannot be given without confirmation that you will have an escort to pick you up from the unit, take you home and remain with you overnight.
There are no disclaimers that you can sign. Also, it is not possible to request for a general anaesthetic unless it was planned by your referrer in advance (e.g. a complex therapeutic procedure), and/or it was proven from a past endoscopy that you did not tolerate the procedure even with higher doses. Even if you did not tolerate the procedure before, it can be repeated on a senior doctor’s list who can provide higher doses which can work very effectively. If a general anaesthetic is required, your procedure may be delayed by a substantial period of time, sometimes by many months. Please speak to the doctor who referred you if you have any concerns.
Before you agree to this procedure, you will have the opportunity to speak with the endoscopist so that you are aware of the reason the procedure is being done, the alternatives and the problems that can occur. For most people a gastroscopy is a simple and safe procedure.Very rarely, complications can occur. These include chest infections, damage or perforation (a hole) in the oesophagus, stomach or duodenum wall, allergy to sedative medication, bleeding or damage to teeth. Serious complications such as a perforation or bleed occur at a rate of 1 in 10,000, so the procedure is considered very safe.
Although gastroscopy is the best procedure to help diagnose or exclude many problems, no procedure is perfect. There is a very small risk that we might miss something during your procedure.
If you decide not to have the procedure it is very important that you inform the Endoscopy Unit as soon as possible and also the clinician who requested, it. However, if the procedure is not performed then it is possible that the cause of your symptoms will not be diagnosed.
Sometimes a barium swallow or a CT scan can be performed as an alternative to a gastroscopy, these procedures allow for the oesophagus shape and function to be measured, but they are not the same as endoscopy as they provide different information. Further, an important disadvantage is that tissue samples cannot be taken with a scan so important information can be missed. Also, it is possible that the doctor asks for both endoscopy and scan as they look at the oesophagus in different ways.
You will have a pre-admission appointment in the weeks before your admission. This is to make sure you can have an anaesthetic safely. We will give you advice about how to take your usual medications before your procedure. We will give you advice about how to take your usual medications before your procedure including if you are taking blood thinning medication.
Please tell staff at your pre-admission appointment about all the medications you are taking.
It is very important that you follow the dietary advice below before the procedure so that your oesophagus and stomach are as empty as possible before the procedure. The vast majority of patients require a standard 6-hour fast. If you have not been given specific instructions otherwise then follow the preparation below (number 1).
1. Standard procedure
You must not eat anything for six hours before your procedure. You can continue to drink clear fluids up to 2 hours before the procedure (not including milk but cordial and black tea/coffee are acceptable).
If food or fluid remains at the time of the procedure and we are unable to remove it during endoscopy, the procedure may need to be abandoned and postponed and you will be asked to fast for a longer period. We may place a thin tube into the oesophagus to help drain any material that remains.
If you are attending for a specialised procedure or you have food in your stomach at your first procedure despite a standard fast you will be asked to follow one of two dietary plans:
2. 1 day diet
From this point until after your procedure you must not eat anything and can drink clear fluids only. Clear fluids include tea (no milk), coffee (no milk), squash, non-alcoholic drinks, carbonated drinks, water, clear soups, Bovril®, and Oxo®.
3. 3 day diet
You must have a liquid diet and no solids for 3 days before the procedure. Options include liquid nutritional supplements (such as Fortisip® or Ensure®), soups, juices and milkshakes. On the last 24 hours, you wil be asked to drink only water or clear juices (e.g. cordial flavoured water). This will be discussed with you during your outpatient appointment before the procedure. Please ask if you are unsure what you can eat.
If you are taking any blood thinning medications such as warfarin, clopidogrel, rivaroxaban, apixaban or any others you should continue these unless we give you specific instructions about stopping them. But please inform us so that a decision can be made what to do about them. If you are having endoscopy with treatment or with a lot of biopsies, these medications may need to be stopped in advance. The doctor referring you will need to decide if it is safe to just stop them and for how long, or if you need to replace them with something else whilst you withhold them.
If you are diabetic and take insulin, it is important that you continue taking your insulin but it is suggested that you reduce your doses on the night before and on the day of the test. If you take diabetic tablets, please do not take them on the day of the gastroscopy until after it has been done.
Please continue taking acid reducing medications such as omeprazole and lansoprazole unless you are told to stop them. Please inform your doctor if you are taking them so a decision can be made in advance.
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 gastroscopy you will be taken to the consenting room where you will meet the endoscopist and be asked to sign a consent form.
Sometimes, due to emergencies and other unforeseen circumstances, your appointment may be delayed, or very rarely cancelled on short notice. We try our best to see everyone on time but please understand that delays and unforeseen circumstances can occur and we ask for your patience in these instances.
By law we must ask you to sign a consent form. This confirms that you agree to have the procedure, understand what it involves and the risks associated with them. The endoscopist will explain all the risks, benefits and alternatives before he or she asks you to sign the form. This is also an opportunity for you to ask any questions you may have regarding the procedure.
Once a decision is made about whether the procedure will be undertaken with throat spray or sedation and your escort situation is confirmed, 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 must wait in the waiting room and cannot be present in the room. In some circumstances, they might be permitted in the room up until it is time for you to be sedated, then they will be asked to kindly leave.
If you are having throat spray, a local anaesthetic will be sprayed onto the back of your throat and you will then be asked to lie on the trolley, on your left side.
After a few seconds your throat will go numb, which can sometimes feel a little unpleasant. You will also need to remove glasses or dentures if you have them. One of the nurses will attach some equipment to you so we can monitor your blood pressure and your oxygen levels.
If you are having sedation, the endoscopist will administer the medicines via a small needle in the back of your hand or in your arm. This will take a few minutes to work. You will also be given a small amount of oxygen during the procedure.
The endoscopist will start the procedure by passing the camera into your mouth. The endoscopist will put air into the stomach to make it easier to see the stomach lining.
It should not be painful but it may feel uncomfortable. The pressure of the endoscope on the back of the throat can be uncomfortable, as can air in the stomach.
If you have had sedation 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.
If you have had throat spray, the nurse will accompany you to the discharge lounge and you will be able go home immediately. Unless you are unsteady on your feet or require assistance with walking and travelling, you will be able to go home unaccompanied. You will need to wait until the numb feeling has worn off before eating and drinking (usually 45 minutes).
In both cases, one of the doctors or nurses will come to explain the results of your gastroscopy. It is not always possible for the doctor to come out, particularly if there is a busy list, but a nurse will always take you through the report, and if necessary, the doctor can give you an advice sheet for aftercare and details of who to contact should you have any problems.
If you have had sedation you must bring someone with you who can to take you home and stay with for 24 hours after the procedure.
Once you arrive home you may eat and drink as normal.
Do read page five and six regarding medication.
Do ask for an interpreter if you require one. Hospital policy states family or friends cannot interpret on behalf of the patient.
Do ensure you have someone to take you home and stay with you after the procedure, if you are having sedation.
Do not drink milk four hours before the procedure.
Do not bring large sums of money or valuables to the hospital as we cannot accept responsibility for loss or damage.
Do not drive for 24 hours if you are having sedation. Please have someone to take you home in a car, taxi or public transport.
Do not drink alcohol for 24 hours after sedation is given.
Do not drive a car, operate heavy machinery or make important decisions for 24 hours after sedation is given.
If you have any problems after the procedure, such as bleeding, black tarry stools or pain, please contact us as soon as possible.
Contact information is provided below.
Endoscopy Booking Team (Monday to Friday 09:00-17:00)
Direct line: 020 3456 7022
Switchboard: 08451 555 000 / 020 3456 7890 ext. 67022
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
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Page last updated: 03 November 2025
Review due: 31 October 2027