Skip to main content

Before Colonoscopy

Medically reviewed by Last updated on Jul 4, 2022.


Before a colonoscopy,

your colon needs to be cleaned out. This is called bowel prep or colon prep. You may need to start your bowel prep 1 to 2 days before your colonoscopy, or the night before. Your bowel movements should look yellow to light brown and be liquid. You should not have solids in your bowel movements.

Call your doctor if:

  • You cannot finish your bowel prep.
  • Your bowel movements are not clear after you finish your bowel prep.
  • You have a fever or feel sick.

Types of bowel prep:

You may need any of the following medicines to help clean out your colon:

  • Polyethylene glycol is a laxative medicine that helps you have soft and frequent bowel movements. This medicine may come in a large container of liquid. You may need to drink this medicine over 4 to 6 hours. Ask your healthcare provider how to take this medicine.
  • Bisacodyl is a laxative medicine that will make it easier for you to have a bowel movement. It may be given with polyethylene glycol as a pill or a suppository.
  • Magnesium citrate is a laxative medicine that will help you have soft and frequent bowel movements. It may be given alone or with other laxative medicines.

Self-care during bowel prep:

  • Plan your bowel prep. Start your bowel prep as directed by your healthcare provider. Give yourself plenty of time to drink the entire amount of medicine. You should expect to empty your bowels frequently. Be sure that you have access to a nearby bathroom.
  • Drink all of the medicine. The medicine is in the correct dose to clean out your bowels. Drink the medicine slowly if you start to feel nauseated. The taste of the medicine may make it difficult for you to drink. Ask your healthcare provider about sports drinks or juices that the medicine can be mixed with.
  • Wear warm clothing if needed. It is normal to get the chills while you drink the medicine. Warm clothing can help make you more comfortable.
  • Prevent soreness in your rectum. Your rectum may get sore because you are wiping so often. Use soft wipes and wipe gently.
  • Drink more liquids as directed. You may become dehydrated from having frequent bowel movements. Ask your healthcare provider how much liquid you need during your bowel prep.

Clear liquids before a colonoscopy:

Your healthcare provider may tell you to drink only clear liquids 1 to 2 days before your colonoscopy. Clear liquids are liquids that you can easily see through. Do not drink clear liquids that are blue, red, or purple. Do not eat or drink solid foods, milk, milk products, or juice with pulp. The following are examples of clear liquids:

  • Water
  • Gelatin
  • Clear soft drinks, such as ginger ale
  • Clear juice without pulp, such as apple juice
  • Broth
  • Oral rehydration solution
  • Sports drinks

Other ways to prepare for your colonoscopy:

  • Arrange for someone to drive you home and stay with you after your procedure.
  • Your healthcare provider will tell you what medicines you should or should not take before your colonoscopy. Talk to your healthcare provider before you stop or change any of your medicines. The following are general guidelines:
    • Diabetic medicines may need to be stopped or their dose changed, on the day of your colonoscopy.
    • Blood thinners may need to be stopped 7 to 14 days before a colonoscopy to prevent bleeding.
    • You will need to stop taking medicines that contain aspirin or iron for 7 days before your colonoscopy.
    • Heart and blood pressure medicines are usually taken on the day of the procedure with a sip of water.

© Copyright IBM Corporation 2022 Information is for End User's use only and may not be sold, redistributed or otherwise used for commercial purposes. All illustrations and images included in CareNotes® are the copyrighted property of A.D.A.M., Inc. or IBM Watson Health

The above information is an educational aid only. It is not intended as medical advice for individual conditions or treatments. Talk to your doctor, nurse or pharmacist before following any medical regimen to see if it is safe and effective for you.

Learn more about Before Colonoscopy

Care guides

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.