Colonoscopy Procedure: What to Expect
Colonoscopy is a safe and highly effective procedure that allows your doctor to examine the lining of your large intestine (colon and rectum) for polyps (irregular growths), inflammation, or cancer. The test is recommended to start when you turn age 45 and every few years after this depending on what was found, family history, symptoms, etc. The test previously had been recommended to start at age 50, but was lowered to 45 due to colon cancer being found in younger people at an increasing rate.
A colonoscopy can feel intimidating, but understanding what to expect — especially how to prepare — can make the experience easier and more successful. In this article, we will explain the preparation for the colonoscopy and the procedure itself.
Colonoscopy Preparation And Why It Matters
The key to a successful colonoscopy is a clean colon. This means following a bowel prep for colonoscopy to empty your intestines so your doctor can see clearly. If the bowel isn’t adequately cleaned out, the procedure might need to be repeated or important findings, like a polyp or even cancer, could be missed.
How Do I Prepare And What Can I Eat Before a Colonoscopy?
You’ll need to modify your diet in the days leading up to your colonoscopy to ensure the colon is adequately cleaned out. Here's a general timeline:
2–3 Days Before: Begin eating low fiber foods for colonoscopy prep, such as white rice, white bread, eggs, poultry, and fish. Avoid fruits, vegetables, seeds, nuts, and whole grains.
1 Day Before: Start on a clear liquid diet for the colonoscopy. No solid foods and be sure you can see to the bottom of cup or bowl of the liquid you are consuming. This would mean things like water, broth, tea, black coffee (no cream), clear juices without pulp, and sports drinks. You can also have Jell-O or plain gelatins (no red or purple colors) and ice pops.
How to Prep for a Colonoscopy
There are several types of colonoscopy prep kits available, and your doctor will choose the one that best fits your health needs. Most involve drinking a special laxative solution, often in two doses (a split-dose regimen). Common prep solutions include PEG-based preps like GoLYTELY®, MiraLAX® (with a sports drink), or sodium sulfate-based formulas like Suprep®. Your instructions will be specific so be sure to follow the instructions you will be given.
How Do I Make the Colonoscopy Prep Drink Easier to Take?
Chill the prep drink and sip it through a straw to improve taste.
Suck on lemon wedges or rinse your mouth with water between sips.
What Happens If My Bowel Prep Isn’t Complete?
If your colon is not fully cleaned out, the exam may not be effective. Your doctor may:
Reschedule the colonoscopy.
Perform it with limited visibility (and potentially miss small polyps).
Recommend repeating the procedure sooner than usual.
If you're having trouble completing the prep, contact your doctor’s office as soon as possible — there is often advice to help you finish it safely.
What to Expect During a Colonoscopy Procedure
After checking in and completing paperwork you will change into a gown and be brought into the procedure room. Most centers now use the expertise of an Anesthesiologist to sedate you during the procedure. They will ask you questions and you will be hooked up to a few monitors to watch your heartrate, oxygenation, and pressure. An intravenous will be inserted and you will be given sedation through this IV. The most typical medications put you into a very restful sleep throughout the entire procedure. The colonoscopy typically takes about 20 to 45 minutes. Your doctor will use a thin, flexible camera to examine the colon. If polyps are found, they may be removed at the same time.
Afterward you’ll be brought to a recovery area and then the doctor will often review everything with you. Most centers will ask that someone accompany you to drive you home after the procedure. Mild bloating or cramping is normal and usually passes quickly.
The Importance of Colonoscopy Prep
Colonoscopy is one of the most powerful tools we have to detect and prevent colon cancer. While the prep isn’t anyone’s favorite part, it’s an essential step in ensuring the procedure is accurate and effective. If you have any questions about how to prep for a colonoscopy, what to eat, or which prep kit is right for you, don't hesitate to reach out to your Gastroenterologist.
Written by Dr. David Beyda, MD.
Dr. Beyda is a board-certified physician with extensive experience in both internal medicine and gastroenterology. He is licensed to practice in New York and holds active certifications from the American Board of Gastroenterology.