How to Prep for a Colonoscopy: Diet Tips, When to Start, and More

A colonoscopy is the recommended screening test for detecting polyps and colorectal cancer. Preparation requires cleansing the colon and following your provider’s specific instructions, which may include temporarily stopping certain medications or supplements, shifting to a low‑fiber diet in the days before, using a clear‑liquid diet and bowel‑clearing agents the day before, and arranging transportation and post‑procedure care. Closely following these directions improves the exam’s accuracy and reduces the chance of needing a repeat procedure.

1. What to do 1–2 weeks before your colonoscopy

Usually you will not need to change your diet 1–2 weeks before the test, but your provider may ask that certain medications and supplements be stopped about a week beforehand. Medications that increase bleeding risk—such as NSAIDs (for example ibuprofen), aspirin, and prescription anticoagulants—are often held for several days; the exact timing depends on the specific drug and the reason for therapy, so consult the clinician who prescribes it. You may also be asked to stop supplements such as iron, fiber products, and fish oil because they can interfere with the exam. Confirm with your doctor in advance which medications and supplements to stop and when.

2. Diet changes in the few days before your colonoscopy

About three to five days before your colonoscopy you may be advised to follow a low‑fiber diet to reduce residual bowel contents and simplify bowel preparation. Avoid high‑fiber items such as granola, nuts, seeds, whole‑grain breads and rice, and fruits or vegetables with skins or seeds; choose lower‑fiber options like milk, cheese, white bread and rice, applesauce, chicken, and clear broth. In the 24–48 hours immediately before the procedure, avoid red or purple foods and beverages, which can persist in the colon and be mistaken for blood. Your physician or care team will provide specific instructions on allowable foods and precise timing.

3. What to do the day before your colonoscopy

The day before your procedure you will be on a clear‑liquid diet and begin the prescribed bowel‑preparation. Preparations vary by provider and may include laxative tablets, powders mixed into clear fluids, or premixed solutions taken at scheduled times over one or two days. The regimen typically works within a few hours and causes frequent bowel movements; the goal is to clear stool until the output is only clear liquid. Follow all instructions exactly and complete the entire course even if your bowels appear empty. Maintain hydration with water or electrolyte drinks, confirm whether you should stop any medications the day before, and contact your provider with any questions.

4. Diet on the morning of your colonoscopy

Patients are generally asked to avoid eating or drinking on the day of their colonoscopy. Some preparation protocols, however, require an additional bowel-prep dose the morning of the procedure. Your physician or care team will advise you if a morning dose is needed and will tell you when to stop all oral intake.

5. Tips for the day of your colonoscopy

Wear loose, comfortable clothing and avoid jewelry or watches that must be removed. Ask your provider which anesthesia or sedative will be used so you understand likely grogginess and whether you’ll need extra help at home. Plan to rest for the remainder of the day and follow any post‑procedure dietary instructions. You will not be able to drive yourself home, so arrange transportation in advance and confirm whether the facility requires your driver to remain on site. If you cannot arrange a companion, ask your care team about available transportation resources. If anxiety about the preparation is preventing screening, discuss alternative tests with your clinician—these can detect cancer but generally cannot remove precancerous polyps as a colonoscopy can.