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Getting ready for a colonoscopy: why, the prep, the day of, and after
For anyone who has a colonoscopy coming up, who has been told they should be screened for colorectal cancer, or who is driving someone home from one. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, part of the NIH) says a colonoscopy is a procedure in which a doctor uses a flexible tube with a camera to look inside your rectum and colon, to find the cause of symptoms or to screen for colon polyps and colorectal cancer. This page passes on, by name, what NIDDK says: why doctors use it and when screening starts; your medicines, the special diet and the clear liquids; the bowel prep and the ride home; what happens during the procedure; and recovery, results, the risks, and when to get care right away. It builds the words to say and the questions to ask, and prints a card for the fridge.
A word with a dotted line under it, like this, opens its official definition, quoted from a U.S. government glossary.
Right now
- Trouble breathing, chest pain, fainting, or heavy bleeding with dizziness? Call 911 (ours).
- After a colonoscopy: severe pain in your abdomen, fever, bloody bowel movements that do not get better, bleeding from the anus that does not stop, dizziness or weakness? NIDDK says to seek medical care right away. Delayed bleeding can happen up to 2 weeks after (NIDDK).
- Side effects keeping you from finishing the bowel prep? NIDDK says to call a health care professional. Use the number on your written instructions.
- It is all too much, or you are thinking of ending your life? Call or text 988, any hour (ours).
More help
- The belly, on this site: Colon polyps · Bleeding in the digestive tract · Hemorrhoids · Ulcerative colitis · Crohn’s disease · An upset stomach: find the right page.
- Getting there and getting ready: Rides to care · My medicines list · Symptom diary · Get ready for your appointment.
- If the news is hard: When the doctor says cancer.
- Care and costs: When you need a doctor and can’t pay · Medical bills.
- In a crisis: Help right now (988, 911). All our free tools.
An upset stomach, and not sure this is the right page? The pages on this site for throwing up, diarrhea, heartburn and constipation, on one list.
This page and its wording were written with AI (Claude) for Scarlet Beast (our AI policy). No doctor or nurse has reviewed it. The facts were read on October 17, 2026 on NIDDK’s Colonoscopy page (NIH) and its Spanish version, both last reviewed in August 2023 and saying the same things; the cards also point to NIDDK’s Flexible Sigmoidoscopy, Virtual Colonoscopy and Colon Polyps pages. The numbers NIDDK gives (screening from age 45; less than one hour; 30 to 60 minutes after; perforation about 3 and bleeding about 15 in every 10,000 screening colonoscopies; delayed bleeding up to 2 weeks) are NIDDK’s, from the studies it cites. Ours: 911 for trouble breathing, chest pain, fainting, or heavy bleeding with dizziness; asking ahead whether any medicine should change, and never stopping one on your own; reading the instructions a week ahead; asking the center about your ride; asking who tells you the results and when your next test is; the card; 988 when it is too much; health centers when money is tight; and the order of the steps. What we left out: bowel prep names, laxative names, brands, doses, and clinical pages for providers. This page saves nothing and loads no trackers.