Pre-Colonoscopy Diet: Day Before the Procedure
The day before your colonoscopy, you should follow a low-residue/low-fiber diet for breakfast and lunch, then switch to clear liquids only for the evening meal and continue clear liquids until the procedure. 1, 2
Dietary Approach Based on Timing
Morning and Midday (Day Before Colonoscopy)
- Eat a low-residue/low-fiber diet for early and midday meals on the day before your colonoscopy 1, 2
- This liberalized approach is well-supported when using split-dose bowel preparation regimens 3
Foods to AVOID All Day Before Colonoscopy
- High-fiber foods including cereals, beans, peas, nuts, and seeds 1, 2
- Raw or dried fruits and vegetables 1, 2
- Red meat, poultry, and vegetables (particularly important in the evening before) 4
- Solid foods or dairy products once you begin the bowel preparation 5
- Anything colored red or purple 5
- Alcohol 5
Evening Meal (Day Before Colonoscopy)
- Switch to clear liquids only for your evening meal and continue until the procedure 2
- Clear liquids can be consumed until 2 hours before the colonoscopy 3, 5
Important Medication Considerations
- Discontinue iron supplements at least 7 days before the colonoscopy, as iron residue creates dark, sticky stool that obscures polyp detection 1, 2, 6
- Avoid taking other laxatives while using your prescribed bowel preparation 5
Evidence Supporting This Approach
The recommendation for a low-residue diet (rather than strict clear liquids all day) is based on strong evidence showing comparable or superior bowel preparation quality with better patient tolerance 3, 7. A 2019 randomized trial demonstrated that a normocaloric low-fiber diet the day before colonoscopy achieved better adequate preparation rates (95.7% vs 89.1%) compared to clear liquids, while also reducing hunger and excessive fluid-intake perception 8.
Multiple studies confirm that dietary restrictions beyond one day before colonoscopy provide no additional benefit 1, 2, making the one-day restriction both effective and more tolerable for patients 7.
Foods You CAN Eat (Low-Residue Examples)
While the guidelines don't exhaustively list permitted foods, low-residue typically includes:
- White bread, refined cereals
- Well-cooked vegetables without skins
- Lean proteins (though avoid red meat and poultry the evening before) 4
- Gelatin is specifically beneficial and positively associated with better preparation 4
Critical Timing Rule
Stop ALL fluid consumption at least 2 hours before your colonoscopy to minimize aspiration risk 5. The evidence shows that clear liquids consumed up to 2 hours before sedation do not increase gastric volume or aspiration risk 3.
Special Considerations for High-Risk Patients
If you have conditions that increase risk of poor preparation—including cirrhosis, Parkinson disease, dementia, diabetes, constipation, or prior inadequate preparation—your physician may recommend more restrictive measures, such as clear liquids only for the entire day before colonoscopy 2, 6.