Preparing for Colonoscopy and Gastroscopy Procedures

Information for patients

Please read at least five days before your procedure.

In preparation for your colonoscopy, the bowel needs to be flushed clean so that the doctor can see the inside of your colon clearly.

Following these instructions carefully, all that will remain in your bowel will be clear or yellow to greenish fluid.

To be effective you must drink all the Glycoprep-C provided even if you think you are clear after only drinking some of it.

Remember to stay near a toilet after commencing the Glycoprep-C, as diarrhoea will occur.

Individual responses to laxatives may vary and may work within 30 minutes or up to three hours.

A vital part of this preparation is the extra fluids that you drink. Not only does this prevent dehydration, it forms an important part of the cleansing process.

If you are regularly troubled by constipation, please tell us.


  • If you are taking iron tablets please stop ten days prior to your procedure.
  • If you are taking stool bulking agents such as Metamucil or Normacol please stop ten days prior to your procedure.
  • If you are taking blood thinning medications such as Aspirin, Warfarin, Dabigatran (Pradaxa), Clopidogrel (Plavix), or Dipyridamole (Persantin), and we have not given you information about stopping, please contact us as soon as possible.
  • Please continue to take all other medicines as prescribed by your doctor.•
  • If you are a diabetic patient please click here for more information.

Tips for taking Glycoprep-C

  • If you feel bloated, try a short walk.
  • If you feel cold or shivery, wrap up warmly.
  • If you feel nauseated, have a break or slow down drinking the Glycoprep.
  • Cleaning your teeth and tongue may help or use a straw.
  • One or two barley sugar sweets may help with the taste.
  • Anal soreness may occur due to multiple bowel motions. Apply Vaseline to anal area before starting Glycoprep-C to minimise this.

On the day of your appointment come to the Day Stay Unit, 2nd Floor Clinical Services Building.

Please phone the Booking office (07 343 7742) if you have any problems. 

5 Days before your admission

  • Take your regular medications
  • Start low fibre diet (click here for guide)
  • Avoid eating nuts and food with seeds or skins, (e.g., tomato, kiwifruit, corn, and graining breads)
  • Do not drink red or purple drinks until after your procedure

4 Days before your admission

As above

3 Days before your admission

As above

2 Days before your admission

  • Take your regular medications
  • Continue low fibre diet
  • Drink plenty of fluids

1 Day before your admission

  • You may have a low fibre breakfast, then take two Bisacodyl laxative tablets with a large glass of water.
  • Eat an early light lunch. Do not eat after 12 midday, until after your procedure.
  • Drink at least ten glasses of clear fluids during the day (see diet sheet). After midnight you can continue to drink water. 
  • Take your regular medications 1 ½ hours prior to beginning, or 1 ½ hours after completing Glycoprep-C, to allow for absorption.
  • Diabetics on metformin and/or gliclazide, do not take the evening dose.
  • Disregard the instructions on the Glycoprep-C packets. Dissolve the content of each packet of Glycoprep-C in one litre of tap water (total three litres). Refrigerate all three litres if you wish. You may add a cordial to flavour such as lemon or lime (not red or purple).
  • At 4pm, start drinking two litres of the Glycoprep solution. You should drink a glass every five to ten minutes aiming to complete two litres in two hours. It is important that you take all two litres of Glycoprep-C. 

Day of procedure 

  • For a morning admission you must take the third litre of Glycoprep-C between 4am and 5am.
  • For an afternoon admission you must take the third litre of Glycoprep-C between 9am and 10am.
  • Continue drinking water up until one hour before your admission to hospital to prevent dehydration. 
  • Take regular medication with a small amount of water.
  • Do not take your diabetes medication or insulin unless you have been advised to do so. Please bring it with you to the hospital.
  • Discharge time is generally two to four hours from your admission time.
  • As you are given sedation, you cannot drive and you must have a responsible adult to collect you from the Day Stay Unit and take you home. They should remain with you for the rest of the day. 
  • You cannot wait outside for your transport, catch a taxi, or bus alone.
  • If you have OSA, bring your CPAP machine.
  • On admission, please tell us if you are taking sleeping tablets, steroids, opioids, or immunosuppressants.