Two-Day Bowel Preparation for Your Urology Surgery or Procedure

Time to Read: About 2 minutes

This information explains how to do a 2-day bowel preparation to empty your colon before your urology surgery or procedure.

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Buy supplies

  • 3 (10-ounce) bottles of magnesium citrate. Magnesium citrate is an over-the-counter laxative. You can buy it at your local pharmacy without a prescription.
  • Clear liquids. For a list of clear liquids you can drink, read the section “Follow a Clear Liquid Diet.”
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2 days before your surgery

Start following a clear liquid diet

Start following a clear liquid diet 2 days before your surgery or procedure. A clear liquid diet includes only liquids you can see through. Examples are listed in the “Clear Liquid Diet” table.

While you’re following a clear liquid diet:

  • Do not eat any solid foods.
  • Try to drink at least 1 (8-ounce) cup of clear liquid every hour you’re awake.
  • Drink different types of clear liquids. Do not just drink water, coffee, and tea.
  • Do not drink any liquids you can’t see through, such as milk or smoothies.
  • Do not drink sugar-free liquids unless you have diabetes and a member of your care team tells you to.

How to follow a clear liquid diet if you have diabetes

Ask the healthcare provider who manages your diabetes:

  • What to do while you’re following a clear liquid diet.
  • If you need to change your dose of insulin or other diabetes medication, if you take them.
  • If you should drink sugar-free clear liquids.

Check your blood sugar level often while you’re following a clear liquid diet. If you have questions, talk with your healthcare provider.

Clear liquid diet
 OK to haveDo not have
Soups
  • Clear broth, bouillon, and consommé.
  • Anything with pieces of food or seasoning.
Sweets
  • Gelatin, such as Jell-O®.
  • Flavored ices.
  • Hard candies, such as Life Savers®, lemon drops, and peppermints.
  • All other sweets.
Drinks
  • Clear fruit juices, such as lemonade, apple, cranberry, and grape juices.
  • Soda, such as ginger ale, 7UP®, Sprite®, and seltzer.
  • Sports drinks, such as Gatorade® and Powerade®.
  • Black coffee or plain tea without milk or creamer.
  • Water, including carbonated (fizzy) and flavored water.
  • Clear nutritional drinks, such as Boost® Breeze, Ensure Clear™, Pedialyte®, and Diabetishield®.
  • Juices with pulp.
  • Nectars.
  • Smoothies or shakes.
  • Milk, cream, and other dairy products.
  • Nut milks, plant milks, non-dairy creamers, and other dairy alternatives.
  • Drinks with alcohol.

Drink magnesium citrate

At 2 days before your surgery or procedure, drink 1 (10-ounce) bottle of magnesium citrate.

  • You will probably start having bowel movements within 30 minutes. But, it can take as long as 3 hours before bowel movements start. Make sure to stay close to a toilet during your bowel preparation.
  • Apply petroleum jelly (Vaseline®) or vitamin A&D ointment (A+D® Ointment) to the skin around your anus after every bowel movement. This helps prevent irritation.
  • Drink clear liquids all day until bedtime. You should drink clear liquids at your usual meal times and between meals.
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1 day before your surgery

Keep following a clear liquid diet

Keep following a clear liquid diet the day before your surgery or procedure. If you have diabetes, remember to check your blood sugar level often. Follow any other instructions the doctor who manages your diabetes gave you.

Drink magnesium citrate

At on the day before your surgery or procedure, drink 1 (10-ounce) bottle of magnesium citrate.

  • Make sure to stay close to a toilet during your bowel preparation.
  • Apply petroleum jelly or vitamin A&D ointment to the skin around your anus after every bowel movement.
  • Keep drinking clear liquids all day until bedtime. Drink clear liquids at your usual meal times and between meals.

At , if your bowel movements aren’t clear, drink another (10-ounce) bottle of magnesium citrate.

Your healthcare provider will tell you if you can have anything to drink after midnight the night before your surgery or procedure.

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If you have questions or concerns, contact your healthcare provider. A member of your care team will answer Monday through Friday from to Outside those hours, you can leave a message or talk with another MSK provider. There is always a doctor or nurse on call. If you’re not sure how to reach your healthcare provider, call 212-639-2000.
If you have questions or concerns, contact your healthcare provider. A member of your care team will answer Monday through Friday from to Outside those hours, you can leave a message or talk with another MSK provider. There is always a doctor or nurse on call. If you’re not sure how to reach your healthcare provider, call 212-639-2000.

For more resources, visit www.mskcc.org/pe to search our virtual library.

Two-Day Bowel Preparation for Your Urology Surgery or Procedure - Last updated on March 26, 2026
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Last Updated

March 26, 2026

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