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Magnesium Citrate Bowel Preparation (Afternoon)

Dr. Bharat Pothuri Medically Reviewed by Dr. Bharat Pothuri, MD, FACG

Learn how to use magnesium citrate for an effective afternoon colonoscopy prep. Follow expert guidelines for a smooth, successful procedure.

Schedule Appointment 832-632-4070

Video Instructions

Written Instructions

General Instructions

2 Weeks Before the Procedure
Foods No change
Liquids Drink plenty of water

1 Week Before the Procedure
Foods

No Nuts or Seeds - berries, cashews, corn nuts, peanuts, pecans, popcorn, walnuts

Low Fiber Diet

  • Foods - white bread, cheese, eggs, yogurt
  • Soups - clear vegetable, chicken or beef broth
  • Vegetables - cooked without skin like mashed potatoes
  • Fruits - pureed fruits without skin like applesauce
Liquids Drink plenty of water
Medications
  • Take as usual unless otherwise instructed
  • Hold - Anti-Diarrheal Medication - Imodium, Kaopectate, Pepto-Bismol
  • Hold - Iron Tablets
  • Hold - Multivitamins
  • Hold - GLP1 Agonist Medication:
    • Dulaglutide (Trulicity)
    • Exenatide (Byetta)
    • Exenatide Extended Release (Bydureon BCise)
    • Liraglutide (Victoza)
    • Lixisenatide (Adlyxin)
    • Semaglutide (Ozempic, Wegovy, Rybelsus)
    • Tirzepatide (Mounjaro)

Pharmacy

  • Fill or buy preparation medication
  • Pick up 3 days before your procedure

1 Day Before the Procedure
Foods
  • Clear Liquid Diet
  • Soups - clear vegetable, chicken or beef broth
  • Juices - clear only without pulp
Liquids
  • Drink plenty of water
  • No alcohol
  • No red or purple colored drinks
Medications
  • Hold - Oral Diabetes Medication
  • Insulin - Take ½ the dose the entire day
  • Blood Pressure Medication - The pre-anesthesia team (PAT) will instruct you on how to take your blood pressure medications.
  • All other medications - continue as normal

Procedure Day
Foods No food or liquids the day of the procedure

Medication Instructions

Attention
Expected Symptoms Do not stop the bowel preparation
  • Abdominal Pain
  • Bloating
  • Cramps
  • Diarrhea
  • Gas
  • Nausea
Take
Generic Simethicone
or
Brand Name Gas-X
Chewable Tablets Only

Take one of the following based on the tablet strength available:

  • 80mg x 4 tabs
    • OR
  • 125mg x 3 tabs
    • OR
  • 250mg x 2 tabs

Chew tablets completely before taking the first dose.

First Dosage → 10PM - 12AM
Step 1 10PM - 11PM

Drink 1st 10 ounce bottle of Magnesium Citrate
Step 2 11PM - 12AM

Drink 16 ounces of water
Take
Generic Simethicone
or
Brand Name Gas-X
Chewable Tablets Only

Take one of the following based on the tablet strength available:

  • 80mg x 4 tabs
    • OR
  • 125mg x 3 tabs
    • OR
  • 250mg x 2 tabs

Chew tablets completely before taking the second dose.

Second Dosage → 4AM - 6AM
Step 1 4AM - 5AM

Drink 2nd 10 ounce bottle of Magnesium Citrate
Step 2 5AM - 6AM

Drink 16 ounces of water

12AM
Foods No food or liquids after midnight except prep solution
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Frequently Asked Questions

How to take magnesium citrate for bowel prep?

Drink the full bottle (10 oz) of magnesium citrate, followed by at least 8 ounces of clear liquid. Stay hydrated and expect frequent bowel movements within a few hours.

How long does it take to empty bowels after magnesium citrate?

Bowel movements typically start within 30 minutes to 6 hours. The cleansing process continues until stool is clear, usually requiring multiple trips to the bathroom.

Why is magnesium citrate no longer used for colonoscopy prep?

Magnesium citrate is less effective than newer bowel preps and poses risks of electrolyte imbalance, dehydration, and kidney issues, especially in older adults or those with health conditions.

How much magnesium citrate to clean out bowels?

A full 10 oz bottle is typically recommended, but some cases may require a second dose. Always follow your doctor's instructions and drink extra fluids to stay hydrated.

When is the best time to take magnesium citrate?

Take it in the evening before your colonoscopy, around 4 PM-6 PM, ensuring enough time for bowel movements to clear the intestines before the procedure.