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What is a gastroscopy?

A gastroscopy is a medical procedure during which a thin, flexible tube called an endoscope is used to look inside the stomach. It is also known as an endoscopy.

The endoscope has a light and a camera on one end. The camera is used to relay images of the inside of your body to a television monitor.

A gastroscopy is a very common procedure.

These pages focus on a gastroscopy, specifically. Read more about other types of


Why you might need a gastroscopy

A gastroscopy may be recommended if you have symptoms that suggest a problem with the stomach. This could be difficulty swallowing (

) or persistent abdominal pain. The procedure can help to diagnose the underlying cause of these symptoms.

A gastroscopy can also be used to treat various problems of the gut. Doctors can pass tiny tools down the endoscope to:

  • repair bleeding ulcers and veins
  • widen the oesophagus if there are blockages
  • provide nutrition if you are unable to eat food in the normal way
  • remove non-cancerous growths (polyps) or early-stage cancerous tumours

Read more about why a

gastroscopy may be necessary

What happens during a gastroscopy?

A gastroscopy is usually performed as an outpatient procedure so you will not have to spend the night in hospital.

It is often carried out under sedation, which means you will not be asleep during the procedure but you will be very drowsy and have little awareness of what is going on. Alternatively, your throat can be numbed with a local anaesthetic spray.

The doctor carrying out the procedure will place the endoscope in the back of your mouth and you will be asked to swallow the first part of the tube. The endoscope is then guided down your oesophagus and into your stomach.

A gastroscopy can take around 20-40 minutes to perform.

Read more about

how a gastroscopy is performed


A gastroscopy is a very safe procedure and serious complications such as infection or internal bleeding are rare, occurring in only around 1 in 1,000 cases.

Read more about the possible

risks associated with a gastroscopy

Risks of gastroscopy

A gastroscopy is a very safe procedure and the risks of serious complications are small.

A gastroscopy that is being used to diagnose a condition (diagnostic gastroscopy) has a 1 in 1,000 chance of causing a serious complication.

Because of its more invasive nature, a gastroscopy that is being used to treat a condition (therapeutic gastroscopy) has a higher risk. But this is still relatively small, at around 1 in 100.

Possible complications include:

  • adverse effects from sedation
  • infection
  • bleeding
  • perforation (tearing)


Sedation is usually a safe procedure, but it can occasionally cause complications which can include:

  • feeling or being sick
  • a burning sensation at the site of the injection
  • small particles of food falling into the lungs and triggering an infection (aspiration pneumonia)
  • irregular heartbeat
  • breathing difficulties

Very rarely, the complications arising from sedation can result in stroke, although this is extremely unlikely, occurring in 1 out of 25,000 cases.


Occasionally, during a gastroscopy bacteria can enter the bloodstream through small tears and cuts in body tissue that were formed during the procedure. In most cases, the bacteria do not cause serious problems and are killed by the immune system.

However, in rare cases, the bacteria can travel to the heart and infect the lining, muscles and valves of the heart. This type of infection is known as


Symptoms of endocarditis include:

  • high temperature (fever) of 38°C (100.4°F) or above
  • chills
  • an unusual sounding heartbeat (murmur)
  • fatigue
  • night sweats
  • aching joints and muscles

Endocarditis can usually be treated with injections of antibiotics.

Read more about the

treatment of endocarditis


Sometimes, the endoscope can accidentally damage a blood vessel, causing it to bleed.

The source of bleeding can usually be repaired using a further gastroscopy, in the same way that bleeding varices or an ulcer is repaired. Blood transfusions may also be required to replace lost blood.


During a gastroscopy, there is a small risk of the endoscope tearing the tissue inside your oesophagus, abdomen or chest.

The warning symptoms include:

  • neck pain
  • pain when swallowing
  • abdomen pain
  • high temperature
  • breathing difficulties

If the perforation is not severe, it can normally be left to heal by itself. You may be given antibiotics to prevent an infection occurring at the site of the tear.

If the perforation is more serious (indicated by severe pain that does not respond to painkillers), then surgery may be needed to repair it.

How is a gastroscopy performed?

You will usually receive instructions on how to prepare for a gastroscopy along with your appointment letter. If you are unsure about anything, call the hospital.


If you are referred for a gastroscopy, you will need to stop taking any prescribed medicines for indigestion at least two weeks beforehand. This is because medication can mask some of the problems that the gastroscopy could show up. You can continue to take antacids up until your endoscopy.

If you are taking any of the following medications, you should telephone the endoscopy unit before your appointment because special arrangements may need to be made:

  • any medication that is used to treat diabetes, such as insulin or metformin
  • blood-thinning medication (medication that is used to prevent blood clots), such as
    low-dose aspirin

You should not wear nail polish on the day of your appointment because it interferes with a device that is attached to your finger to monitor your oxygen levels.


It is important that your stomach is empty so that the whole area can be seen clearly. You will be asked not to eat anything for six hours and drink nothing for two hours before having a gastroscopy.


You will usually be sedated during a gastroscopy. This means you will be very drowsy during and after the procedure so it's a good idea to arrange for someone to bring you home and to stay with you for at least 12 hours after a gastroscopy.

The procedure

A gastroscopy is usually carried out by a nurse and an endoscopist (a health professional who specialises in performing endoscopies). You will meet the nurse before the procedure and she will be able to answer any questions that you may have.

You should remove any glasses, contact lenses and false teeth. A nurse may then spray your throat with a local anaesthetic spray and insert a small plastic mouth guard to protect your teeth.

You will be asked to lie down on your left-hand side and the nurse will attach a small probe to your finger. This measures your oxygen level and heart rate.

At this point, you will normally be given an injection of sedatives into your arm. This will make you feel very drowsy so that you will be mostly unaware of the procedure and will probably have no memory of it. However, you will still be able to follow any instructions given to you by the endoscopist or nurse.

The endoscopist will insert the endoscope into your throat and tell you to swallow it to help move it down into your oesophagus.

Diagnosing a condition

If the gastroscopy is being used to diagnose a certain condition, air will be blown into your stomach once the endoscope is inside. This allows the endoscopist to see any patches of redness, holes, lumps, blockages or other abnormalities.

If abnormalities are detected, a biopsy can be taken (a tissue sample from the problem area) to send to the laboratory for closer inspection under a microscope. You will not feel anything during a biopsy.

Treating bleeding varices

If you have bleeding varices, the endoscopist will first use the endoscope to locate the site of the bleeding.

If the bleeding varices are located in your oesophagus, they can normally be treated using a technique called band ligation. This involves passing a small rubber band down the endoscope, which is used to seal the base of the varices and cut off the blood supply to prevent further bleeding.

If the bleeding varices are located in your stomach, the site of the bleeding will be injected with a chemical called cyanoacrylate. Cyanoacrylate is the active ingredient in the extra-strength glues (‘superglues’) that are sold in shops. It is also very useful in sealing holes or tears in body tissue.

Treating bleeding ulcers

If you have bleeding ulcers, one of a number of techniques may be used to treat them. For example:

  • a probe may be passed through the endoscope to apply heat or small clips to stop the bleeding
  • a weak solution of adrenaline may be injected around an ulcer to help activate the clotting process, narrow the arteries and enhance blood clotting

During these procedures you may also receive an injection of a fast-acting acid-reducing medication, called a proton-pump inhibitor, to prevent bleeding recurring.

Narrowed oesophagus

If you have a narrowed oesophagus, the endoscopist can pass instruments down the endoscope to stretch and widen it. These instruments can also be used to insert a rigid balloon or stent (a hollow plastic or metal tube) to hold the walls of your oesophagus open.


A gastroscopy takes around 20-40 minutes to perform. The endoscope will then be removed and you will be taken to a recovery room until the effects of the sedation have worn off.

You may not remember much about the procedure after you come round.

If you received a gastroscopy as part of a treatment, you may be given a series of tests to assess how effective the treatment was and check for any complications.

These tests may include:

  • a chest
  • a measure of your heart rate
  • a blood pressure test

Depending on your individual circumstances, you will then either be transferred to a hospital ward or discharged (sent home).

Even if you feel very alert, the sedative can stay in your blood for 24 hours and you may experience further episodes of drowsiness.

It is important that you do not drive a vehicle, operate heavy machinery or drink any alcohol during this time.

Depending on what type of procedure you have had, it may be several days before you can resume a normal diet. The endoscopy nurse will give you more information about your specific dietary recommendations.


If the gastroscopy was used to diagnose a condition, a further appointment may be made so you can discuss the results with the doctor, or the results of the gastroscopy may be sent to your doctor.

Why is a gastroscopy used?

A gastroscopy can be used to check symptoms or confirm a diagnosis (known as a diagnostic gastroscopy), or it can be used to treat a condition (therapeutic gastroscopy).

Checking symptoms

A diagnostic gastroscopy is usually recommended if your symptoms suggest that you have a problem with your stomach, which may also affect your oesophagus (gullet) or the first section of your small intestine.

Symptoms that are often investigated include:

  • difficulties swallowing or pain when swallowing (
  • persistent abdominal pain
  • persistent nausea (feeling sick) and vomiting
  • unexplained weight loss

A diagnostic gastroscopy can also be used if your doctor suspects that you have bleeding inside your stomach or small intestine. Persistent bleeding can significantly reduce the number of red blood cells in your body. This is known as anaemia.

Symptoms of anaemia include:

  • feeling tired all the time
  • breathlessness
  • pale skin
  • irregular heartbeats

In some cases, bleeding inside the gastrointestinal (GI) tract can be sudden and massive, and cause symptoms such as:

  • vomiting blood
  • passing stools (faeces) that are very dark or ‘tar-like’
  • a sudden, sharp pain in your abdomen that gets steadily worse

These symptoms usually require immediate investigation with a diagnostic gastroscopy.

Confirming a diagnosis

A diagnostic gastroscopy is also used to help confirm (or rule out) suspected conditions, such as those listed below.

  • Stomach ulcer
    (also known as peptic ulcer disease) – open sores that develop on the lining of the stomach and small intestine.
  • Gastro-oesophageal reflux disease (GORD)
    – a condition where stomach acid leaks back up into the oesophagus.
  • Barrett's oesophagus – where abnormal cells develop on the lining of the oesophagus.
  • Portal hypertension – where the blood pressure inside the liver is abnormally high. This leads to the development of abnormally swollen veins (varices) on the lining of the stomach and oesophagus.
  • Stomach cancer
    oesophageal cancer
    – the endoscope can be used to remove samples of suspected cancerous tissue for testing. This is known as a biopsy.

Therapeutic gastroscopy

The two most common uses of a therapeutic gastroscopy are:

  • To stop bleeding inside the stomach or oesophagus. Bleeding is commonly caused by a stomach ulcer,
    gastro-oesophageal reflux disease
    or enlarged veins (varices) on the lining of the oesophagus or stomach.
  • To widen a narrowed oesophagus that is causing pain or swallowing difficulties (dysphagia).

Your oesophagus can become narrowed or blocked for a number of reasons, including

mouth cancer
lung cancer
or an infection, such as tuberculosis or herpes simplex.

A gastroscopy that is used to widen the oesophagus is also known as a ‘gastroscopy with oesophageal dilatation’.

Other uses of therapeutic gastroscopy include:

  • treating cases of early-stage stomach or throat cancer by removing any tumours (advanced cases will require more extensive surgery)
  • removing non-cancerous growths (polyps) that are causing an obstruction
  • removing objects that have become lodged in the oesophagus or stomach
  • providing nutrients by way of a feeding tube, when a person is unable to eat in the normal way

Important: Our website provides useful information but is not a substitute for medical advice. You should always seek the advice of your doctor when making decisions about your health.