Colonoscopy prep

The prep empties the colon so the doctor can see the whole lining. The ASGE puts it plainly: the bowel must be clean so the doctor does not miss precancerous growths called polyps. A poor prep can hide polyps and produce a false normal result, and the American Cancer Society says people who quit the prep early may need the colonoscopy repeated. When a prep is inadequate, the Multi-Society Task Force recommends rescheduling within twelve months, or within about three if the colonoscopy was for an abnormal screening test.

• Medications. Tell the office about aspirin, arthritis medications, blood thinners, diabetes medications, and iron. The office will have instructions (ASGE). For blood thinners, Cleveland Clinic's sheet says to speak with the prescriber at least two weeks ahead and never stop them on your own. For diabetes medicine, call the doctor who manages your glucose; the prep diet can change your doses. Stop iron five days before (Cleveland Clinic).
• GLP-1 medications. The GI societies have not told patients to stop them on their own; they say more data are needed and the office decides. Ask.
• The ride. Arrange one now. You cannot drive after sedation, and Cleveland Clinic's sheet says you cannot take a taxi or leave alone either; without a driver the exam may be canceled. Plan on three to four hours from arrival to discharge.

Switch to low-fiber food. Cleveland Clinic says stop seeds, nuts, beans, raw vegetables, and popcorn two or three days out; the ACS starts at three to five days and adds granola, whole-grain bread, and fruit or vegetables with skin. Stop fiber supplements such as Metamucil or Citrucel. The Task Force notes that for most people the diet restriction can be limited to the day before, and that low-fiber food works as well as clear liquids that day, so follow what your sheet says here.

Nothing solid all day. A clear liquid is anything you can see through: water, apple or white grape juice, fat-free broth, black coffee or tea, clear sodas, sports drinks, plain gelatin, popsicles without fruit or cream. Nothing red or purple, because those colors can look like blood in the colon (Cleveland Clinic). No milk, cream soups, or alcohol.

Then the first dose of the prep in the evening. Most kits are split-dose: half the night before, half the morning of. The ASGE says split dosing gives the best cleansing and improves the doctor's ability to find polyps, and the Task Force recommends it for everyone.

• Mix it ahead and chill it; cold goes down easier (Cleveland Clinic, MSKCC).
• Use a straw if you have one (MSKCC).
• Pace it: one 8-ounce glass every 10 to 15 minutes, depending on the kit (Cleveland Clinic).
• If you feel sick, slow down and take a 30 to 45 minute break (MSKCC).
• Only add the flavor pack that came with a polyethylene glycol prep. No ice, sugar, or other flavorings in the solution (Cleveland Clinic).
• Bloating, cramping, nausea, and burning are expected. Petroleum jelly or A&D ointment around the anus after each bowel movement helps (MSKCC).
• Keep drinking water or electrolyte drinks throughout (ACS).

The second dose starts four to six hours before the procedure and finishes at least two hours before it (Task Force). Then stop all liquids. The cutoff varies by center: the ASGE says two to three hours before, Cleveland Clinic's sheets say three, MSKCC says four. Your sheet has your number.

You are done when what you pass is watery, yellow, and clear enough to see through (ASGE, Cleveland Clinic). If it is not clear by the time you leave, call the office and tell them (MSKCC).

I never change an instruction on your sheet. What I do is read the sheet you photograph, text you each day's step on its day, ask whether it happened, hold what you tell me against the call-the-office list, and make sure the ride is real.

No clinician reviewed this page. It restates the ASGE, the US Multi-Society Task Force, the NIH, Cleveland Clinic, MSKCC, and the American Cancer Society pages linked below, and those, and your own sheet, are the documents to trust over anything here.