Gastroscopy: when you need one, preparation, the procedure and risks

What a gastroscopy is

A gastroscopy (also called an upper GI endoscopy or OGD) uses a gastroscope – a flexible tube about 9–10 mm wide with a light and a video camera at the tip. It is passed through the mouth, and a gastroenterologist examines the oesophagus, the stomach and the duodenum, the first section of the small bowel. The image is shown on a high-definition screen.

Small instruments can be passed through a channel in the scope to take biopsies (tiny samples of tissue for laboratory analysis), stop bleeding or remove polyps, so a gastroscopy can both diagnose and treat. Modern scopes offer special light settings and magnification that help reveal early changes in the lining.

When a gastroscopy is recommended

• Warning symptoms – difficulty or pain when swallowing, vomiting blood, black stools, unexplained weight loss, iron-deficiency anaemia (found on a full blood count) or persistent vomiting.
• Ongoing symptoms – heartburn and acid reflux that do not respond to treatment, or upper abdominal pain (dyspepsia), particularly new symptoms after the age of 55.
• Checking a finding – a suspected ulcer, tumour or inflammation seen on a scan.
• Surveillance – Barrett's oesophagus, swollen veins in the oesophagus in cirrhosis, atrophic gastritis, or after treatment of an ulcer or early tumour.
• Diagnosing other conditions – such as coeliac disease (by biopsies from the duodenum) or Helicobacter pylori infection.
• Before certain operations – for example weight-loss surgery or anti-reflux surgery.

Ask in advance whether sedation is offered and whether laboratory analysis of any biopsies is included.

Preparing for the test

Your stomach needs to be empty so the lining can be seen clearly and to reduce the risk of inhaling stomach contents. Your endoscopy team will give you exact instructions, but usually:

• you should not eat for about six hours beforehand; clear fluids such as water are usually allowed until around two hours before;
• tell the team in advance if you take blood thinners, diabetes medicines (including injectable weight-loss medicines that slow stomach emptying) or have any allergies;
• you may be asked to stop acid-reducing tablets (PPIs) about two weeks before if Helicobacter pylori is being tested for – do not stop them unless told to;
• if you are having sedation, arrange for someone to take you home, as you must not drive that day.

Bring a list of your medicines and any previous test results.

What happens during a gastroscopy

Your throat is numbed with a local anaesthetic spray and, if you wish or the doctor advises it, you are given intravenous sedation – a light anaesthetic that makes you relaxed and often unable to remember the test. You lie on your left side and a plastic mouthguard is placed between your teeth.

The doctor passes the gastroscope and gently inflates the stomach with air or carbon dioxide to open it up. You may feel pressure, gagging or bloating, but the test should not be painful and does not interfere with your breathing. It usually takes 5–15 minutes, longer if treatment is carried out.

Afterwards you should wait until the numbness in your throat wears off (usually about an hour) before eating or drinking. After sedation you rest for a while under observation. The doctor usually explains what was seen straight away; biopsy results take one to two weeks.

What a gastroscopy can find

A normal result is valuable too: it rules out serious disease and points towards other causes of your symptoms.

Risks and complications

A diagnostic gastroscopy is a very safe test. The most common after-effects are a mild sore throat and bloating for a few hours. Uncommon complications include:

• bleeding, more likely after a biopsy or polyp removal;
• perforation (a tear in the wall), which is rare and more likely during treatments such as stretching a narrowing;
• a reaction to sedation, or breathing or heart rhythm problems;
• aspiration (stomach contents entering the airways), which is why an empty stomach matters.

Seek urgent help if after the test you develop severe pain in the chest, neck or abdomen, a fever, difficulty breathing, vomiting blood or black stools.

Alternatives

A barium swallow X-ray, a CT scan or capsule endoscopy can provide information in some situations, but none allows a biopsy and none replaces gastroscopy when there are warning symptoms. Helicobacter pylori can also be detected with a breath test or a stool test. Transnasal gastroscopy, using a thinner scope passed through the nose, is offered in some centres and is easier to tolerate without sedation. You can read more about tests in our guide to diagnosis and tests.

When to see a doctor

Ask your GP about a referral to a gastroenterologist if you have:

• difficulty swallowing or food sticking;
• heartburn or upper abdominal pain that continues despite treatment;
• unexplained weight loss or anaemia;
• a family history of stomach or oesophageal cancer.

Vomiting blood or coffee-ground-like material, or passing black stools, needs emergency care. In that situation a gastroscopy is done urgently and often allows the bleeding to be stopped straight away.

Gastroscopy abroad and in Türkiye

Some patients from Bulgaria and other European countries have a gastroscopy – often combined with a colonoscopy on the same day under one sedation – at large accredited hospital groups in Istanbul, frequently as part of a health check-up. Check that the test is performed by an experienced gastroenterologist, that an anaesthetist supervises sedation, that you will receive a written report with images, and how you will be given biopsy results that arrive after you return home. Organisers such as New City Clinic coordinate the hospital, doctor, hotel, transfers and interpreter.