- Prioritize easy-to-digest, low-residue foods such as white rice, eggs, and well-cooked skinless vegetables starting three days before your procedure, then switch to clear liquids only for the final 24 hours.
- Strictly avoid high-fiber foods like whole kernel corn, nuts, and seeds seven days in advance, as well as any products containing red, purple, or blue dyes that can mimic bleeding.
- Contact your gastroenterologist immediately if you experience severe abdominal pain, persistent vomiting, or an inability to pass gas at any point during the bowel preparation.
A strict colonoscopy prep diet is necessary to fully cleanse the bowel and allow for clear visualization of the intestinal lining. Following this dietary protocol ensures that residual stool does not obscure polyps or other abnormalities during the examination.
This process typically involves transitioning from a low-residue diet three days prior to the procedure to a clear liquid diet 24 hours before the appointment. Specific restrictions, such as avoiding red dyes, seeds, and nuts, are critical to ensuring the colon is free of waste for a successful exam.
Failure to follow the prescribed guidelines may result in inadequate preparation, leading to a cancelled procedure or the need for a repeat colonoscopy. Patients taking medications such as blood thinners or diabetes drugs should consult a physician for dosage adjustments to prevent complications during sedation.
Why this diet is required
The Boston Bowel Preparation Scale (BBPS) is used by doctors to rate cleanliness. A low-residue diet limits indigestible plant fiber, ensuring the physician achieves a high BBPS score.
Poor preparation often results in a cancelled procedure and a repeat colonoscopy. This ensures the intestines are clear during inspection and any abnormalities along the intestinal wall can be observed.
To prep for a colonoscopy, the doctor will also prescribe laxative solutions to help clean out the intestines.
Clinical timeline: What to eat and avoid
A colonoscopy prep diet follows a strict timeline to ensure the colon is free of waste.
Phase one: 7 days prior (Elimination Phase)
Seven days before the procedure, you must stop consuming foods that are difficult to digest and linger in the colon. These items can clog the colonoscope even after laxative use.
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Strictly Avoid: Whole kernel corn, popcorn, nuts, and seeds (including sunflower, sesame, and poppy seeds).
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Avoid: Multigrain bread and fruits/vegetables with small seeds (like cucumbers, tomatoes, and strawberries).
Phase two: 3 days prior (Low-Residue Diet)
The semi-liquid, low-residue diet should be adhered to on the third and second day prior to the exam. The types of food to be consumed include:
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Fruit without its peel or seeds, preferably cooked. Examples include apples, pears, and bananas.
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Peeled and cooked vegetables, such as carrots, chayote, potatoes, pumpkin, zucchini, yams, and sweet potatoes.
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Non-whole grains, such as white rice, white bread, and white pasta.
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Skinless, fat-free proteins, including chicken and fish, which should be ground or shredded to facilitate digestion.
In addition, you can consume teas, coffee, and coconut water. Maintain strict hydration to counteract fluid loss from laxatives.
Phase three: 24 hours prior (Clear Liquid Diet)
The day before the colonoscopy, you should adhere to a liquid diet made up of fat-free soups or broths. These can be made with vegetables and proteins, but should be strained, as solid foods should not be ingested.
You can also consume strained, light-colored juices, light-colored gelatin, water, coconut water, and light teas, such as chamomile, anise, or lemon balm.
Red/Purple Dye Protocol: Do not consume anything colored red, purple, or blue (e.g., grape juice, cherry gelatin, red sports drinks), as these can mimic intestinal bleeding during the exam. Stick to green or yellow colors only.
Phase four: NPO (Nothing by Mouth)
You must stop all intake, including water, usually 2 to 4 hours before your scheduled procedure time or as directed by your anesthesia provider. This prevents the risk of aspiration during sedation.
Sample 3-day meal plan
The following table outlines a sample 3-day meal plan for a colonoscopy prep diet.
It is important to remember that on the day of the exam, you should only drink water and light-colored teas up to 4 hours before the scheduled exam time.
Medication management
Patients taking GLP-1 agonists (Ozempic, Wegovy, Mounjaro), insulin, or blood thinners (anticoagulants) must consult their prescribing physician for dosage adjustments during the fasting period. These medications can affect digestion speed or bleeding risk during the procedure.
What to eat after a colonoscopy
After the exam, it is important to maintain a light diet, to drink plenty of fluids, and to avoid high-fat foods.
The gut takes around 3 to 5 days to start working normally again. It is common to experience abdominal discomfort and bloating in the belly during this time. Therefore, you should avoid foods that cause gas within 24 hours of the exam, such as beans, lentils, peas, cabbage, broccoli, kale, eggs, sweets, soft drinks, and seafood.
Emergency Disclaimer: If you experience severe vomiting, inability to pass gas, or severe abdominal pain during prep, contact your on-call gastroenterologist immediately.