A gastroscopy is usually done to investigate the cause of abdominal pain, vomiting or bleeding from the digestive tract, and to make or confirm a diagnosis. Conditions can also sometimes also be treated via gastroscopy — for example, polyps can be removed.

You will be asked not to eat or drink anything for at least 6 hours before the test.

If you are taking any medicines, check with your doctor if it is all right to continue taking them. You may be asked to stop taking medicines that can increase the risk of bleeding for a few days before the test; these include warfarin, aspirin and non-steroidal anti-inflammatory (NSAID) medicines. However, this depends on your individual circumstances, so you should check.

You should also inform the centre performing the gastroscopy if you have any condition that requires you to take antibiotics before dental procedures — you may need antibiotics before gastroscopy too.

Before your gastroscopy, the doctor will discuss the test with you and answer any questions, then you will be asked to sign a consent form allowing the test to be done.

What happens during a gastroscopy?

You will be asked to lie on the table on your left side. You are usually given a sedative and sometimes a pain-reliever medicine by injection into a vein. The sedative will help you to relax, and may put you to sleep. Generally, you will have little recollection of the procedure. In some cases, the test can be done without the sedative and you need to discuss this with the doctor before you sign the consent form.

The back of your throat may be sprayed with a local anaesthetic to make it numb and to help you not to gag. A small mouthguard will be put between your teeth to stop you from biting the endoscope. If you have false teeth (dentures) they will be removed before the procedure.

The endoscope will be placed into your mouth and you will be instructed to swallow it down into your stomach. The tube is just less than a centimetre in diameter and does not enter your windpipe, so there is plenty of room to breathe around it. The doctor will direct air into your stomach via the gastroscope. This will make viewing easier.

Sometimes a special instrument can be inserted through the scope, and a small sample of tissue removed (a biopsy). This is not painful. The doctor may also take photos to refer to later. Some treatments can be performed while the endoscope is in (e.g. removing polyps, controlling blood loss from an ulcer or injecting veins — similar to varicose veins — in the stomach or oesophagus).

The procedure takes about 15 to 30 minutes. After the test you will be transferred to a recovery room and a nurse will care for you until you are awake. You can usually go home after about 2 hours.

Make sure you have someone to drive you home as you will still be drowsy after the test. You should not drive and should plan to rest for the remainder of the day.

Although the doctor may briefly run through the findings of the gastroscopy with you once the sedative has worn off, a follow-up appointment is usually made to discuss the test results more fully.

Very few people experience serious side effects from gastroscopy. You may have a slightly sore throat after the procedure. Air may also be trapped in your stomach causing you to feel bloated. If a biopsy has been taken or treatment performed, there may be minor bleeding. Very rarely, the stomach lining may be torn, and in such cases you would be admitted to hospital and an operation would be performed to repair it.

Reactions to the sedative are also possible, but again rare.