What can a patient consume the day before a colonoscopy?

Pre-Colonoscopy Diet: What Patients Can Consume the Day Before

Patients using a split-dose bowel preparation regimen can consume a low-residue/low-fiber diet for breakfast and lunch the day before colonoscopy, then switch to clear liquids only for the evening meal and continue clear liquids until the procedure. 1, 2, 3

Dietary Approach Based on Preparation Timing

For Split-Dose Regimens (Preferred Method)

Low-residue diet is acceptable for early and midday meals:

• Patients may eat low-residue/low-fiber foods for breakfast and lunch on the day before colonoscopy 1, 2
• Switch to clear liquids only starting with the evening meal 2, 3
• Continue clear liquids until at least 2 hours before the procedure 1, 3

Foods to avoid on the day before colonoscopy:

• High-fiber cereals, beans, peas, nuts, and seeds 2, 3
• Raw or dried fruits and vegetables 2, 3
• Red meat, poultry, and vegetables (particularly on the day before) 4

Clear liquids that are acceptable:

• Water, clear broth, gelatin (consumption of gelatin is actually associated with better preparation quality) 4
• Avoid anything colored red or purple 5
• Avoid dairy products 5
• Avoid alcohol 5

Timing Restrictions

Dietary modifications should be limited to one day before colonoscopy only:

• Additional days of dietary restrictions beyond one day provide no benefit in bowel preparation adequacy 2, 3
• Patients find 1-day restriction more tolerable and easier to comply with 2

Special Considerations for High-Risk Patients

For patients at high risk for inadequate preparation, consider more restrictive approach:

• Clear liquids only for the entire day before colonoscopy 3
• High-risk conditions include: cirrhosis (OR 3.4), Parkinson disease (OR 3.2), dementia (OR 3.0), diabetes (OR 1.8), constipation (OR 1.3), prior inadequate preparation, or opioid use 2, 6

Iron Supplementation

Discontinue iron supplements at least 7 days before colonoscopy:

• Iron creates dark, sticky stool that obscures detection of polyps and lesions 2, 3
• This is a critical step that compromises diagnostic accuracy if not followed 3, 6

Medication Timing

Avoid oral medications within one hour before or after starting bowel preparation:

• Take tetracycline, fluoroquinolone antibiotics, iron, digoxin, chlorpromazine, or penicillamine at least 2 hours before and not less than 6 hours after bowel preparation 5
• Do not take other laxatives while taking prescribed bowel preparation 5

Evidence Supporting Liberalized Diet

The evidence strongly supports that low-residue diet is non-inferior to clear liquid diet:

• Meta-analysis of 1,686 patients showed low-residue diet resulted in significantly higher tolerability (OR 1.92) and willingness to repeat preparation (OR 1.86) with no difference in adequate bowel preparation quality 7
• A 2019 randomized trial demonstrated that normocaloric low-fiber diet was actually superior to clear liquid diet (95.7% vs 89.1% adequate preparation, p=0.04) 8
• Patients consuming low-residue diet reported less hunger and better fluid-intake perception 8

Common Pitfalls to Avoid

Do not unnecessarily restrict diet for more than one day:

• This reduces compliance without improving outcomes 2, 3

Do not consume solid foods less than 6 hours before the procedure:

• This increases aspiration risk 3

Ensure adequate hydration with bowel preparation:

• Split-dose regimen requires drinking at least five 8-ounce cups (40 ounces) of clear liquids after the first dose and at least three 8-ounce cups (24 ounces) after the second dose 5
• Complete all fluid intake at least 2 hours before colonoscopy 5