As GLP-1 receptor agonists like Ozempic (semaglutide) and Zepbound (tirzepatide) become increasingly common in weight management and diabetes care, they bring with them a new challenge to an old routine: colonoscopy prep. While patients may be eager to follow standard instructions for bowel prep, those on GLP-1s often face insufficient bowel cleansing due to delayed gastric emptying and slowed GI transit time — core pharmacologic effects of these medications.
GLP-1s mimic incretin hormones that naturally regulate blood sugar and appetite by slowing gastric emptying and reducing gut motility. While these effects contribute to sustained satiety and improved glycemic control, they also mean that food and prep solutions may remain in the digestive tract longer than anticipated. This creates a perfect storm for colonoscopy preparation: Patients may feel they’ve followed instructions correctly, yet residual material persists in the colon due to the medication’s inherent effects on digestive timing.
In my clinical practice, I’ve noticed a trend: Patients on GLP-1 agonists often present with incomplete prep, which can compromise the visibility of the colonic mucosa and increase the risk of missed pathology. This anecdotal observation is now backed by data.
A 2025 study of over 6,000 patients at 22 endoscopy centers in the U.S. found that patients using GLP-1 medications were significantly more likely to have inadequate bowel preparation, even after adjusting for diabetes and obesity. The American Society for Gastrointestinal Endoscopy (ASGE) has not yet released updated prep guidelines specifically for this population, but many gastroenterologists are now recommending earlier dietary adjustments and a longer prep window.
Successfully navigating colonoscopy prep with GLP-1 patients requires a multifaceted approach that addresses both the pharmacologic challenges and patient education gaps. The following are key considerations when counseling patients on GLP-1s:
1) Stop the medication in advance. Some clinicians advise discontinuing GLP-1 medications five to seven days prior to the colonoscopy. While evidence is still emerging, this strategy may reduce the impact on gut motility and improve prep outcomes.
2) Start prep earlier. Patients may need to begin a clear liquid diet or modified prep protocol 48 to 72 hours in advance, rather than the usual 24-hour prep window.
3) Use lay language when explaining risks. In a recent text exchange with a patient, I explained: “You feel full longer because [the medication] slows down digestion. You don’t want to go through all that and then miss something because you weren’t cleaned out enough.” Simple, clear phrasing helps patients understand why we’re asking them to do more than the handout says.
4) Watch for confusion between weight loss and bowel health. Patients may assume their lighter eating habits mean they are “already empty.” It’s critical to explain that even small meals can linger longer than expected when gut motility is reduced.
5) Adjust educational materials and EMR instructions. Consider flagging GLP-1 use in preprocedure screening checklists and updating prep instructions accordingly.
As clinicians, we must stay ahead of the curve when common medications alter the efficacy of routine procedures. Patient-centered education and protocol adjustments are essential to ensuring effective colorectal cancer screening in the era of GLP-1s.
How are you adjusting your colonoscopy prep protocols for patients taking GLP-1 medications? Share in the comments.
Ashley Ingram-T’Siobbel, DNP, FNP-C, is a family nurse practitioner with over 15 years of experience in primary care. Her special interests are health literacy, patient education, and humanistic health communication.
Collage by Diana Connolly
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