What dietary restrictions are recommended before a colonoscopy?

Dietary Restrictions Before Colonoscopy

For patients at low risk for inadequate bowel preparation, clear liquids are only necessary for the evening meal on the day before colonoscopy—a low-residue/low-fiber diet is acceptable for breakfast and lunch that day, with no dietary restrictions needed earlier. 1, 2

Standard Dietary Approach for Low-Risk Patients

The most recent 2025 guidelines from the American Gastroenterological Association recommend limiting all dietary modifications to just the day before colonoscopy. 1, 3

Day Before Colonoscopy

• Eat a low-residue/low-fiber diet for breakfast and lunch, avoiding high-fiber foods such as cereals, beans, peas, nuts, seeds, and raw or dried fruits and vegetables 1, 2
• Switch to clear liquids only for the evening meal and continue until the procedure 1, 2
• Additional days of dietary restrictions beyond one day provide no benefit in bowel preparation quality 1, 2

Two or More Days Before Colonoscopy

• No dietary restrictions are necessary when using a split-dose bowel preparation regimen 2, 4
• Patients find 1-day diet restriction more tolerable and easier to comply with compared to longer durations 2

Evidence Supporting Liberalized Diet

The shift away from prolonged clear liquid diets is supported by strong evidence. Research demonstrates that bowel preparation quality is noninferior when patients consume a low-residue diet versus clear liquids all day before colonoscopy, with 96.5% achieving good or excellent preparation 5. A large study found no association between foods consumed 2-3 days before colonoscopy and bowel preparation scores 4. Multiple randomized trials show comparable or better bowel cleansing with liberalized diets, though the 2014 Multi-Society Task Force noted heterogeneity in these studies 6.

High-Risk Patients Requiring More Restrictive Approach

For patients at high risk for inadequate bowel preparation, consider clear liquids only for the entire day before colonoscopy. 1

High-Risk Conditions Include:

• Prior inadequate bowel preparation 2
• Chronic constipation (OR 1.3) 2
• Diabetes mellitus (OR 1.8) 2
• Cirrhosis (OR 3.4) 2
• Parkinson disease (OR 3.2) 2
• Dementia (OR 3.0) 2
• Opioid use 2
• Spinal cord injury 2

Suggested High-Risk Regimen:

• Low-residue diet starting 3 and 2 days before colonoscopy 1
• Clear liquids only the entire day before colonoscopy 1
• Split-dose 4L polyethylene glycol-electrolyte lavage solution plus 15mg bisacodyl the afternoon before colonoscopy 1

Critical Timing Considerations

Clear liquids can be consumed until 2 hours before anesthesia/sedation without affecting residual gastric volume or increasing aspiration risk. 6

• The American Society of Anesthesiologists evidence-based guideline confirms that clear liquid ingestion until 2 hours before sedation does not affect gastric emptying 6
• Solid foods should be avoided for at least 6 hours before anesthesia 6, 1
• Bowel preparation should be completed at least 2 hours before the procedure 1, 2

Additional Recommendations

Iron Supplementation

Discontinue all oral iron supplements at least 7 days before colonoscopy to prevent dark, sticky stool that can obscure polyp detection 1, 2, 7

Split-Dose Preparation

Use a split-dose bowel preparation regimen for all patients, with the second portion beginning 4-6 hours before colonoscopy 1, 3. Split dosing provides superior efficacy and higher adenoma detection rates compared to single-dose regimens 6.

Patient Education

Provide both verbal and written instructions for all components of colonoscopy preparation, as this is an independent predictor of adequate bowel preparation quality 6, 1

Common Pitfalls to Avoid

• Unnecessarily restricting diet for more than one day before colonoscopy reduces compliance without improving outcomes 1, 2
• Failing to use split-dose regimen, which is demonstrably superior to single-dose administration 1
• Not completing bowel preparation at least 2 hours before the procedure increases aspiration risk 1, 2
• Continuing iron supplements within 7 days of the procedure compromises diagnostic accuracy 2, 7
• Providing only written instructions without verbal reinforcement reduces compliance 6