During gastroscopy, the doctor may numb the back of your throat by spraying on some local anaesthetic, or give you an anaesthetic lozenge to suck. You may be given a sedative to help you to relax. This is usually given by an injection into a vein in the back of your hand. The sedative can make you drowsy, but it does not "put you to sleep". It is not a general anaesthetic.

You lie on your side on a couch. You are asked to put a plastic mouth guard between your teeth. This protects your teeth and stops you biting the endoscope. The doctor will then ask you to swallow the first section of the endoscope. Modern endoscopes are quite thin and easy to swallow. The doctor then gently pushes it further down your oesophagus and into your stomach and duodenum.

The video camera at the tip of the endoscope sends pictures to a screen. The doctor watches the screen for abnormalities of the oesophagus, stomach and duodenum. Air is passed down a channel in the endoscope into the stomach to make the stomach lining easier to see. This may cause you to feel "full" and want to belch.

The doctor may take one or more biopsies of parts of the inside lining of the gut - depending on why the test is done and what they see. This is painless. The biopsy samples are sent to the lab for testing, and to look at under the microscope. The endoscope is then gently pulled out.

A gastroscopy can take around 20-40 minutes to perform. However, you should allow at least 2 hours for the whole appointment to prepare, give time for the sedative to work (if you have one), for the gastroscopy itself, and to recover. A gastroscopy does not usually hurt, but it can be a little uncomfortable, particularly when you first swallow the endoscope.