GLP-1 Before a Colonoscopy or Endoscopy: Prep and Questions

If you take a GLP-1 such as Ozempic, Wegovy, Mounjaro or Zepbound and have a colonoscopy or upper endoscopy coming up, tell the GI team when you book it, because these medicines can affect both your bowel prep and how empty your stomach is under sedation. Most people won't have to stop the medicine, according to current guidance, but some get different prep or diet instructions. The team can only give you those if they know.

GI procedures raise two separate GLP-1 issues: food left in the stomach (matters most for upper endoscopy and sedation) and stool left in the colon (matters for colonoscopy). They need different questions.

Why GLP-1s matter for endoscopy: food left in the stomach

Upper endoscopy (EGD) sends a camera through the mouth into the stomach and the first part of the small intestine. Most people have it under sedation. GLP-1 medicines slow gastric emptying, so after a normal overnight fast some people still have food in their stomach.

That causes two problems. The doctor can't see the stomach lining clearly, and some procedures get stopped and rescheduled. More seriously, under deep sedation retained food can be aspirated into the lungs. FDA labels for GLP-1 medicines now carry a warning about rare aspiration reports in people having procedures under general anesthesia or deep sedation, including people who followed standard fasting instructions.

How common is retained food? A 2025 review in the Journal of Clinical Medicine summarizes several studies. In one of them, people on semaglutide had significant retained gastric contents during routine upper endoscopy about 24% of the time, compared with about 5% of non-users. Aspiration itself was rare in the large datasets the review covers. One study of nearly 20,000 elective gastroscopies counted four clinically evident aspiration events in total. So the realistic risk is more often a cancelled or repeated procedure than a catastrophe, and both are worth avoiding.

Can Ozempic or Mounjaro affect colonoscopy prep?

Colonoscopy prep means clearing the colon with a laxative solution so the doctor can spot polyps. If the bowel isn't clean enough, small polyps can be missed and you may have to do the whole thing again.

A 2026 meta-analysis in Clinical Endoscopy pooled 12 observational studies with nearly 124,000 patients. Inadequate bowel prep happened in about 10.9% of GLP-1 users vs 6.4% of non-users. After adjusting for age, sex and diabetes or obesity, the odds were about twice as high. The same analysis did not find a statistically significant rise in repeat colonoscopies. All of the studies were observational, and prep regimens varied, so the link is real but its size is uncertain.

Researchers suspect slower gut movement, plus the constipation many people get on these drugs. If you're already battling constipation on a GLP-1, tell the GI team. That's useful information when they're choosing your prep.

Do I need to stop my GLP-1 before a colonoscopy or endoscopy?

Here's how the guidance has changed:

• 2023: The American Society of Anesthesiologists suggested holding weekly GLP-1s for a week before elective procedures. It noted that the evidence was thin.
• Late 2023 / early 2024: An American Gastroenterological Association (AGA) rapid clinical practice update said people without symptoms who follow standard fasting can generally go ahead without stopping. It offered a clear-liquid diet the day before as an alternative to holding the drug. For people with nausea, vomiting or bloating, it suggested checking the stomach with ultrasound where that's available.
• October 2024: Multi-society guidance from five groups, including the ASA and AGA, said most patients can continue their GLP-1 before elective surgery and endoscopy. For higher-risk patients (those early in treatment or after a dose increase, on higher doses, or with current GI symptoms), it described a 24-hour liquid diet and other precautions, and said the decision is a shared one between the procedure, anesthesia and prescribing teams.

Endoscopy units vary. One center may ask for 24 hours of clear liquids, another may do a quick stomach ultrasound, and another may protect the airway differently. That's why your unit's written instructions beat anything you read online, including this post.

Questions to ask the GI team before prep day

Copy these into your notes before the scheduling call:

About the medicine

1. "I take [product, strength] every [day/week]. My last dose was [date]. Do you want me to do anything differently, or should I ask my prescriber?"
2. "I started recently / had a dose increase in the last couple of months. Does that change anything?"
3. "I also take [insulin / other diabetes medicines]. Who is giving me instructions for those during prep?"

About the stomach (upper endoscopy and sedation) 4. "Should I be on clear liquids for longer than your standard instructions say?" 5. "Do you check stomach contents with ultrasound before sedation here?" 6. "If there's food in my stomach, what happens? Do we stop and reschedule?"

About the colon (colonoscopy) 7. "I get constipated on this medicine. Should my prep or low-fiber diet start earlier, or be different?" 8. "What should my output look like by the end of the prep, and who do I call if it isn't clear?" 9. "If the prep is inadequate, will I need to repeat the colonoscopy, and when?"

About symptoms 10. "Who do I call if I start vomiting or can't finish the prep?" Vomiting during prep is a reason to call. Don't just push through it.

Write down the answers. If your prescriber and the endoscopy unit say different things, ask them to talk to each other.

What to have ready on procedure day

• Your medication list with the GLP-1 product, strength and date of your last dose. Our pre-op medication note template works for endoscopy too.
• The unit's written diet instructions, plus a note of when you actually started clear liquids.
• A list of any symptoms during prep: nausea, cramping, vomiting, or output that never ran clear.

If you log symptoms in an app like GLPily, you can show the nurse your nausea or constipation entries from the past week instead of trying to remember them.

For surgery under general anesthesia, which raises some different questions, see what your anesthesia team needs to know.

Common questions

Will my colonoscopy be cancelled because I take Ozempic?

Usually not. Current multi-society guidance says most patients can continue their GLP-1. A procedure may be stopped or rescheduled if there's too much food in the stomach or the bowel prep is inadequate. Telling the team early makes both less likely.

Is a colonoscopy riskier than an upper endoscopy on a GLP-1?

They raise different concerns. Upper endoscopy and deep sedation are where retained stomach contents matter most. With colonoscopy, the bigger studied issue is a less clean colon. Many colonoscopies also use sedation, so the stomach question still applies.

Should I do a longer liquid diet just to be safe?

Only if your GI team tells you to. Guidance describes a 24-hour liquid diet for higher-risk patients, but your unit sets the exact plan. Long fasts can also cause trouble if you take insulin or other glucose-lowering medicines.

Do I restart my GLP-1 after the procedure?

Ask before you leave. If you didn't stop, there's usually nothing to restart. If you did pause, get the restart instructions in writing. See restarting a GLP-1 after a break.