Coastal Gastroenterology
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Diet guidance

Diet guide for colonoscopy prep

Easy-to-read guides for each phase of your preparation diet. Choose the section that matches where you are in your prep.

When to follow this phase

Typically the day before your colonoscopy

A clear-liquid diet gives your digestive system a rest while keeping you hydrated and providing some energy. You can see through clear liquids, and they leave no residue in the colon.

Gluten challenge for Coeliac testing

Your doctor is taking biopsies to check for Coeliac disease. For the test to be accurate, you need to keep eating gluten before the procedure.

  • Continue eating normal amounts of wheat, barley, rye, and oats (if you usually eat them).
  • If you are already on a gluten-free diet, speak with your doctor about a formal gluten challenge before the test. A common challenge is the equivalent of 2 slices of wheat bread daily for about 6 weeks.
  • Do not start a gluten-free diet until after your procedure and your doctor has discussed the results with you.
  • The low-fibre and clear-liquid diet instructions still apply, but choose gluten-containing refined options where possible (e.g., white bread, plain wheat biscuits, white pasta) until your prep phase begins.

If you have already cut out gluten, let the clinic know before your appointment. Your doctor may need to reschedule the biopsies or adjust the advice.

Clear liquids you can have

These are typically allowed on a clear-liquid diet. Avoid anything with red, purple, or blue dyes unless your doctor says otherwise.

Hydration

  • Water and sparkling water
  • Clear broths and bouillon
  • Clear fruit juices without pulp
  • Clear sodas and sports drinks

Warm drinks

  • Plain black coffee without milk
  • Plain tea without milk
  • Clear fruit-flavoured drinks without pulp

Light snacks

  • Plain jelly without fruit
  • Ice blocks without fruit or cream
  • Clear boiled lollies

Sweets

  • Honey, sugar, and clear syrup
  • Plain sugar-based drinks

What to avoid

Do not drink or eat anything that is not clear or that leaves residue in the colon.

  • Milk, cream, and non-dairy creamers
  • Orange juice, tomato juice, or any juice with pulp
  • Smoothies, protein shakes, and meal-replacement drinks
  • Soups with noodles, vegetables, or meat pieces
  • Anything red, purple, or blue dyed
  • Alcohol
  • Solid food of any kind

Sample clear-liquid day

Morning

Black coffee or tea, water, clear juice

Midday

Clear broth, jelly, clear sports drink

Afternoon

Water, ice blocks, clear soft drink

Evening

Clear broth, jelly, water until cutoff

What to buy from your pharmacy

0 of 2 purchased

You do not need a prescription for any of these. Tick each item once you have it.

Morning admission (before 12:00 PM)

If your admission time is before 12:00 PM, follow this timetable the day before your procedure.

  1. All dayClear fluids only — no solid food from when you wake up.
  2. 3:00 PMDrink 1 sachet of PICOPREP (or PICOSALAX or PICOLAX) dissolved in 250ml of water, followed by 3 glasses of water over the next hour. Frequent watery bowel motions will occur.
  3. Every hourTo prevent dehydration, continue to drink at least one glass of water or clear fluid per hour.
  4. 6:00 PMDrink a second sachet of PICOPREP (or PICOSALAX or PICOLAX) plus 3 glasses of water as described above.
  5. EveningPrepare 2L of Glycoprep and store it in the fridge.
  6. 9:00 PMDrink 1L of Glycoprep before going to bed.
  7. 5:00 AM (procedure day)Drink the remaining 1L of chilled Glycoprep over about an hour, then clear fluids only until 2 hours before your arrival time.

Afternoon admission (12:00 PM or later)

If your admission is at 12:00 PM or later, use this timetable the day before your procedure instead of the morning list above.

  1. From 10:00 AMClear fluids only — no solid food from this point.
  2. 6:00 PMDrink 1 sachet of PICOSALAX (or PICOPREP or PICOLAX) dissolved in 250ml of water, followed by 3 glasses of water over the next hour. Frequent watery bowel motions will occur.
  3. Every hourTo prevent dehydration, continue to drink one glass of water or clear fluid per hour.
  4. 10:00 PMDrink a second sachet of PICOSALAX (or PICOPREP or PICOLAX) the same way. Frequent watery bowel motions will occur again.
  5. Before bedPrepare 1L of Colonlytely and store it in the fridge overnight.
  6. 7:00 AM (procedure day)Drink the 1L of chilled Colonlytely over about an hour, then clear fluids only until 2 hours before your arrival time.

Hydration tip

Drink plenty of clear fluids throughout the day to stay hydrated. Dehydration can make the prep solution harder to tolerate. If you feel nauseated, take small sips more frequently.