Colonoscopy Prep on a GLP-1

If you are on a GLP-1 and have a colonoscopy, upper endoscopy, or any procedure with sedation coming up, the single most important step is telling the team that is doing it, early, by drug name and dose.

Not on the morning of the procedure. When it is scheduled.

Why it matters

These medications slow how quickly the stomach empties. That is part of how they work, and it matters when you are sedated, because food or fluid still sitting in the stomach is a concern during sedation and anesthesia.

Multi-society clinical guidance published in 2025 on using these medications around procedures moved away from blanket rules toward an individual assessment. It states there is no data to support automatically stopping these medications before elective procedures, and instead weighs factors such as whether you are still escalating your dose, how high your dose is, whether you use a weekly formulation, and whether you currently have gastrointestinal symptoms. It also describes ways to reduce risk without necessarily stopping, including a liquid diet before the procedure and adjustments to anesthesia planning.

Every one of those factors is information your team can only use if they have it.

Do you stop the medication?

That is your procedure team’s decision, not yours, and practices differ.

Some will ask you to continue and extend your clear-liquid period. Some will ask you to hold a dose. The guidance notes that if a weekly medication is held, it would typically be held for a week beforehand, while also acknowledging that the ideal duration is not known.

Do not stop or skip your medication on your own because you have read that you should. Ask. And if you are asked to hold a dose, ask your prescriber what to do about restarting afterward, since a gap can change where you resume. Our guide on taking a break and restarting covers why restarting after a gap usually means stepping back down.

What to tell them, and when

At scheduling, or as soon as you know:

• The exact medication and dose
• Your injection day
• Whether you have recently increased your dose, or are due to
• Whether you have nausea, vomiting, bloating, or constipation right now
• Anything else you take for blood sugar

Ask them directly: “Do you want me to change anything about my GLP-1 or my diet before this procedure?”

Avoid scheduling it after a dose increase

Side effects and slowed emptying tend to be most noticeable after starting and after each dose increase. If you can, avoid booking a procedure in the weeks just after a step up, and avoid stepping up in the weeks before a booked procedure. Ask your prescriber to time things around it. Our guides on dose escalation and when to increase your tirzepatide dose cover how that timing usually works.

Getting through the prep

Bowel preparation is unpleasant at the best of times, and these medications add two complications: nausea, and dehydration.

Follow your team’s prep instructions exactly, including any extended liquid diet they give you because of your medication.

Drink the prep slowly if nausea is a problem, and ask the team in advance what to do if you cannot finish it. Do not simply stop drinking it.

Stay hydrated with clear fluids. Prep causes significant fluid loss, and these medications can add to it through their gastrointestinal effects. Dehydration is the thing that causes real problems on these medications.

Call the team if you vomit repeatedly, cannot keep the prep down, feel very dizzy, or are passing much less urine than usual.

Consider this scenario: someone books a colonoscopy, mentions their GLP-1 only when the nurse asks on the morning of the procedure, and learns they ate solid food the day before because nobody told them to extend their liquid diet. The procedure is postponed. A phone call at the time of booking would have given them clear instructions and a procedure that went ahead.

After the procedure

Ask before you leave when to resume your medication if you were asked to hold it, and when you can return to normal eating. Start with light food.

Our guide on how tirzepatide and semaglutide side effects compare covers the differences between the two medications, which may be relevant to the questions your team asks.

The same applies to other procedures

Upper endoscopy, procedures under sedation at the dentist, and surgery all involve the same issue. Tell every team, every time.

If you take medication for diabetes

If you also take insulin or other medications that lower blood sugar, the fasting and clear-liquid period before a colonoscopy needs its own plan. Not eating while those medications keep working can cause low blood sugar. Ask the clinician who manages your diabetes, as well as your procedure team, exactly what to do with each medication during the prep and on the day. Get the answer in writing well before the prep starts, and bring a list of everything you take to the procedure.

The short version

Tell your procedure team about your GLP-1 when the procedure is booked, by name, dose, and injection day. Current guidance favors an individual decision rather than automatic stopping, and may involve an extended liquid diet or holding a dose. Do not stop on your own, and ask your prescriber how to restart if you are asked to hold. Avoid pairing a procedure with a recent dose increase. Follow prep instructions exactly and stay hydrated.

If you want a provider who will coordinate with your procedure team, TrimRx includes ongoing provider access alongside treatment.

This information is for educational purposes and is not medical advice. Consult with a healthcare provider before starting any medication. Individual results may vary.