Colonoscopy and gastroscopy: what they are, how to prepare, and what to expect

A gastroscopy looks at the top of your digestive system: your oesophagus, your stomach, and the first part of your small intestine. A colonoscopy looks at the bottom: your large bowel, from the rectum all the way along the colon.

Both use a thin, flexible tube with a small camera on the end. Both are done with sedation, and both are usually day procedures, so you come in and go home on the same day. The practical difference is the preparation. A gastroscopy asks you to fast. A colonoscopy asks you to empty your bowel first.

This article provides a general overview of what you can expect. But it’s important to know that every specialist has their own protocol, and yours will give you written instructions specific to you and your health. Where the two differ, follow your specialist. If anything in your instructions is unclear, ring their rooms and ask before you start.

Why your GP or specialist might suggest one

There are four common reasons.

Symptoms that need explaining. For a gastroscopy, that might be heartburn or reflux that has not settled with treatment, trouble swallowing, ongoing pain in the upper abdomen, or persistent nausea. For a colonoscopy, it might be bleeding, a change in bowel habit that has lasted more than a few weeks, ongoing abdominal pain, unexplained anaemia, or weight loss you cannot account for.

A positive bowel screening result. The National Bowel Cancer Screening Program posts a free test kit to people aged 50 to 74 every two years. People aged 45 to 49 are also eligible, but they have to ask for their first kit, either through the National Cancer Screening Register or by asking their doctor. A positive result means the test picked up blood that you would not have seen. It does not mean you have cancer. Blood in a sample can come from several things, and a colonoscopy is how your doctor finds out which one.

Family history. If bowel cancer, polyps or inflammatory bowel disease runs in your family, your GP may suggest starting checks earlier or more often than the screening program does. This is a clinical judgement about your own history, so it is a conversation to have with your doctor.

Keeping an eye on something known. If you have had polyps removed before, or you live with coeliac disease, reflux changes or inflammatory bowel disease, your specialist may schedule repeat procedures at set intervals. This is called surveillance, and the interval is set by what was found last time.

Preparing: what will be asked of you, and roughly when

Prep instructions vary between specialists and between the products they use. The shape of it, though, is fairly consistent.

A week or two before: You’ll be asked for a full list of your medicines, including anything you buy over the counter. Some medicines need adjusting before a procedure: blood thinners, diabetes medicines, iron tablets and certain supplements are the usual ones. Do not stop or change anything yourself. Ring the specialist’s rooms and let them tell you what to do. At Adeney, you’ll also complete an online admission form and take a call from the pre-admission nursing team, who go through your history and anything that needs planning for.

A few days before, for a colonoscopy: Most people are asked to shift to low-fibre food for a couple of days: white bread and rice rather than wholegrains, no nuts, seeds, skins or raw vegetables. It is a short-term change and it makes the next step work better.

The day before, for a colonoscopy: You’ll drink a bowel preparation liquid to clear the bowel out completely, so the camera has a clear view. Plan to be at home with easy access to a toilet for several hours. Many specialists split the dose, with some the evening before and the rest early on the morning of the procedure. You’ll also be asked to keep drinking clear fluids through this period so you stay hydrated.

Fasting: For both procedures you’ll be given a time to stop eating and drinking. Your fasting instructions come from your specialist’s rooms and need to be followed to the letter, because a procedure can be postponed if fasting has not been done properly.

Getting home: Sedation means you must not drive, and you should not go home alone. Arrange for a responsible adult to collect you and stay with you for the first night.

On the day

You’ll be given an arrival time that’s earlier than your procedure time, because there is admission and preparation to do first. Bring your Medicare card, your health fund details, your medicine list and something loose to wear.

At Adeney, patient services will check you in on the ground floor and then you will go to level 1 day surgery admissions area . A nurse takes your observations and goes through your history. Your specialist comes to see you beforehand, confirms what is planned and answers questions. You will also meet the clinician looking after your sedation, who will ask about your health, your medicines and how you have handled sedation or anaesthetic in the past.

The procedure itself is shorter than most people imagine. A colonoscopy usually takes 20 to 45 minutes. A gastroscopy is usually quicker again. If both are being done in the same session, they are done one after the other while you are sedated.

Between admission, the procedure and recovery, most people are on site for several hours. Adeney has a dedicated endoscopy suite alongside its four operating theatres, with Melbourne Pathology and I-MED Radiology on site.

Afterwards

You’ll wake up in the recovery area with a nurse nearby. Most people feel drowsy for a while and clear up over an hour or two. After a colonoscopy it is normal to feel bloated or windy for a few hours, because air is used to open the bowel during the procedure. After a gastroscopy your throat may feel a bit scratchy. Both settle on their own.

You’ll be offered something to eat and drink before you go. Unless you’re told otherwise, most people go back to normal food that day, starting light.

You will not be discharged until you are alert, steady, able to keep fluids down and comfortable, and until your responsible adult is there in person to take you home. Plan not to drive, operate machinery, drink alcohol or sign anything important for at least 24 hours. Sedation stays in your system longer than it feels like it does.

Results: Your specialist will usually tell you what they saw straight after the procedure, and you’ll get it in writing too, because sedation makes conversations hard to hold onto. That’s another good reason to have your support person with you. If tissue samples were taken, those go to pathology and results take longer, usually a few days to a couple of weeks. Your specialist explains those results and what they mean, and writes to your GP. If you have not heard within the timeframe you were given, ring the rooms.

If a polyp is found

Polyps are small growths on the lining of the bowel. They’re fairly common, usually cause no symptoms, and most are harmless. Some types can slowly change over years, which is why they’re removed when they’re found rather than left to be watched.

Removal usually happens during the same procedure, using instruments passed down the colonoscope. The polyp goes to pathology to be examined, and what comes back determines whether you need another colonoscopy and when. For many people the answer is a repeat check in a few years.

Finding and removing polyps is a large part of why colonoscopy is used for bowel screening at all.

Referral, and what it costs

You need a referral from your GP for Medicare to pay a rebate on a specialist consultation. You can ask your GP to refer you to a gastroenterologist who works at Adeney. The list of gastroenterologists accredited at Adeney is on the hospital’s website.

The cost comes in two parts:

The consultation in the specialist’s rooms: This is an outpatient service, and by law private health insurance cannot cover outpatient consultations. Medicare pays a rebate and the specialist sets their own fee, so there may be a gap to pay. Ask the rooms what the consultation will cost when you book it.

The procedure itself: This happens once you’re admitted to hospital as a day patient. At Adeney, eligible Medibank and Bupa members with hospital cover have no additional charge at the point of care for the proceduralist’s fee, the anaesthetist’s fee, inpatient pathology, onsite radiology and inpatient pharmacy. You may still pay an excess or co-payment, which is set by your fund rather than by the hospital, so check your policy.

Adeney welcomes patients from other health funds on standard fee terms. If you don’t hold private health insurance, endoscopy is available on a self-funded basis, and you’ll be given a written estimate before you commit to a date so you know what you are agreeing to.

Before any admission, your treating specialist and the hospital take you through informed financial consent, so the number is in writing and known well before the day.

Common questions

What is the difference between a gastroscopy and a colonoscopy?

A gastroscopy examines the upper digestive tract: the oesophagus, stomach and the first part of the small intestine. A colonoscopy examines the large bowel. Both use a flexible camera and both are usually done as day procedures under sedation. The preparation is what differs most: a gastroscopy needs fasting, a colonoscopy needs the bowel cleared first.

How long does a colonoscopy take?

The procedure itself usually takes 20 to 45 minutes. Allow several hours at the hospital in total, covering admission, preparation, the procedure and recovery before you are cleared to go home.

How do I prepare for a colonoscopy?

Typically you shift to low-fibre food for a couple of days, drink a bowel preparation the day before and sometimes early on the morning of the procedure, then fast for a set period beforehand. Your specialist will give you written instructions specific to you, including any changes to your medicines. Those instructions take precedence over any general guide, including this one.

Will I be awake?

You’ll be sedated. Most people remember very little of the procedure. Before you start, a clinician assesses you for anything that changes how your sedation should be planned, and talks you through the risks and benefits. Sedation is given and monitored in line with Australian and New Zealand College of Anaesthetists guidelines.

Can I drive myself home?

No. You must not drive for at least 24 hours after sedation. You also need a responsible adult to collect you and stay with you for the first night.

Do I need a referral?

You need a referral from your GP for Medicare to pay a rebate on the specialist consultation. A GP referral generally lasts 12 months from your first appointment with that specialist. You can ask your GP to refer you to a specialist who works at Adeney.

I am 46. Can I do bowel cancer screening?

Yes. People aged 45 to 49 are eligible for the National Bowel Cancer Screening Program, but the first kit has to be requested rather than posted automatically. You can request it through the National Cancer Screening Register or ask your doctor for one. From 50 to 74, kits arrive in the mail every two years.

My screening test came back positive. What happens now?

A positive result means blood was found in the sample. It is not a diagnosis. The next step is to see your GP, who will refer you to a specialist for a colonoscopy to find out what caused it. This should happen promptly.

What does zero out-of-pocket cover for a colonoscopy at Adeney?

For eligible Medibank and Bupa members with hospital cover, there is no additional charge at the point of care for the proceduralist, the anaesthetist, inpatient pathology, onsite radiology and inpatient pharmacy. Your fund excess may still apply.

What if I do not have private health insurance?

Adeney provides endoscopy on a self-funded basis, with a written estimate given before you book so you know the cost in advance.

Can I ask for my procedure to be done at Adeney?

Referrals are written to specialists rather than to hospitals, so ask your GP to refer you to a gastroenterologist who works at Adeney. If you are already seeing a specialist, ask their rooms whether they hold admitting rights there when your procedure is being booked. Where a procedure happens depends on your clinical needs and where your specialist operates, so Adeney will not be the right fit for everyone, but asking the question is a normal part of arranging your care.

Sources

1. Australian Government Department of Health, Disability and Ageing, National Bowel Cancer Screening Program: about the program and lowered eligible age. health.gov.au

2. Australian Commission on Safety and Quality in Health Care, Colonoscopy Clinical Care Standard (2025), including the guide for consumers. safetyandquality.gov.au/clinical-care-standards/colonoscopy

3. Services Australia, Referrals for specialist treatment. servicesaustralia.gov.au/referrals-for-specialist-treatment

4. Australian Government Department of Health, Disability and Ageing, What private health insurance covers. health.gov.au/topics/private-health-insurance/what-private-health-insurance-covers

5. healthdirect, Polyps. healthdirect.gov.au/polyps

6. Better Health Channel (Victorian Government), Bowel cancer. betterhealth.vic.gov.au

Last updated: September 2026