Written and medically reviewed by: Assoc. Prof. Cengiz Dibekoğlu, MD, General SurgeryLast updated:
Colonoscopy Preparation
How bowel cleaning works — step by step
Bowel prep clears mucus and solid residue so the colon lining is fully visible. Poor prep means missed polyps and often a repeat procedure. Follow your center’s written protocol exactly.
Outcomes of any surgical or interventional procedure may vary from person to person. Please seek a detailed consultation with your physician before any procedure.
© Cengiz Dibekoğlu — illustrative; not for unauthorized use
Figure summary
This educational figure shows: Bowel prep.
Key points
Bowel cleaning — step by step
Most protocols use three phases: low-fiber diet, clear-liquid day, then PEG solution or tablet prep. Skipping a phase ruins quality.
- 1–3 days before: restrict fiber, skins, whole grains, legumes
- Prep day: clear fluids only — no pulp (no pulpy juice, chunky soup) and no grains/seeds (no fiber particles)
- Evening and/or morning: complete PEG or tablet protocol on schedule
- Goal stool: clear yellow fluid without solid pieces
Pulp-free, seed-free clear liquids
On the clear-liquid day the goal is to leave no pulp or particles in the bowel. Avoid pulpy citrus juice, fruit puree, chunky soup, milk, yogurt, and fiber-rich foods. Filtered clear broth, pulp-free jelly, transparent PEG solution, and water are appropriate. Red or purple dyes can confuse stool color — follow your center’s list. Pulp and seeds ruin prep quality; target stool is clear yellow fluid.
- Key note inside
Taking PEG solution
Polyethylene glycol (PEG) is drunk in large volume over set hours. Nausea is common — slow the pace and contact your team rather than stopping early. Most protocols aim to finish the last dose 4–6 hours before the procedure.
- Key note inside
Medications
Blood thinners (aspirin, clopidogrel, warfarin, DOACs) need a personalized plan — do not stop on your own. Diabetes drugs and insulin are adjusted on prep day. Iron supplements are usually stopped about a week ahead. Some blood-pressure medicines may be taken with a small sip of water in the morning.
Procedure day
Nothing by mouth in the morning unless your team says otherwise. An IV line is placed for sedation; bring a companion — do not drive the same day.
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Appointment / info
This page is for education. It is not medical advice and does not replace a visit with your physician.
Medical editor: Assoc. Prof. Cengiz Dibekoğlu, MD · Last medically reviewed: August 2026 · English patient-education chapter.