What Should You Do If You Throw Up While Drinking Colonoscopy Prep?

The short answer: Stop drinking for a short while, rinse your mouth, and let your stomach settle. The FDA labels for GoLYTELY, SUTAB, and PLENVU tell patients to pause or slow down when nausea or bloating hits, then resume. If you cannot keep the solution down, or you vomit more than once, call the endoscopy unit that scheduled you. Do not skip the rest of the prep or cancel on your own.

What should you do in the first few minutes after you vomit?

Stop drinking. Sit upright, rinse your mouth with water, and give your stomach time to calm down. The prep labels do not set a fixed waiting time, so follow any timing your unit wrote on your instruction sheet.

Then look at what you are passing. If you have already had several watery bowel movements, some of the prep did its job before you vomited. That detail helps the nurse decide what you should do next.

When you restart, drink more slowly than before. Smaller sips at longer intervals are what the labels describe. Write down the time you vomited and roughly how much of the dose you finished. The unit will ask for both.

Do not double up to make up for what came back. No prep label tells patients to take an extra dose after vomiting, and that choice belongs to your care team.

What do the prep labels actually say about nausea and vomiting?

Every major prep lists nausea and vomiting as common side effects. The instructions for handling them vary by product.

• GoLYTELY (4 L PEG): The GoLYTELY label on DailyMed says nausea, abdominal fullness, and bloating occur in up to 50% of patients. It sets a pace of 8 ounces every 10 minutes. If severe bloating, distention, or abdominal pain occurs, the label says to slow or temporarily stop drinking and contact your healthcare provider.
• SUTAB (tablets): The SUTAB label says that if you have nausea, bloating, or cramping, you should pause or slow the rate of drinking the additional water until symptoms diminish.
• PLENVU (1 L PEG): The PLENVU label says to stop drinking temporarily, or drink each portion at longer intervals, if severe bloating or discomfort develops. It lists nausea, vomiting, dehydration, and abdominal pain as its most common adverse reactions.
• SUPREP and CLENPIQ: The SUPREP label lists nausea and vomiting among its most common adverse reactions in adults. The CLENPIQ label tells patients to contact their provider if significant vomiting or signs of dehydration occur during or after dosing.

All five labels share one instruction for clinicians. If a patient develops significant vomiting or signs of dehydration, the clinician should consider post-colonoscopy lab tests for electrolytes, creatinine, and BUN.

GoLYTELY also lists rare but serious problems linked to vomiting. They include bleeding from a Mallory-Weiss tear in the esophagus and lung changes after vomiting and inhaling the solution. Forceful, repeated vomiting is a reason to stop and call, not to push through.

When should you call the endoscopy unit?

Call if any of these apply. The first comes straight from the GoLYTELY medication guide, which tells patients to report vomiting that prevents them from keeping down the solution.

• You cannot keep the solution down after a pause and a slower restart.
• You vomited more than once, or you vomited up most of a dose.
• You are passing little or no watery stool after the first dose.
• You are not sure you can finish the second dose on time.

The National Institute of Diabetes and Digestive and Kidney Diseases says the same in plain terms: call a health care professional if side effects keep you from finishing the prep. Most units have an after-hours line printed on the instruction sheet.

Timing matters for the call. The 2025 US Multi-Society Task Force bowel prep recommendations say the second split dose should begin 4 to 6 hours before the colonoscopy and finish at least 2 hours before it starts. Calling early leaves room to adjust. Our colonoscopy prep tips cover the full split-dose schedule.

Which dehydration and electrolyte signs need urgent care?

Vomiting plus watery diarrhea can drain fluid fast. The medication guides for SUPREP, SUTAB, PLENVU, and CLENPIQ list the same warning signs of fluid loss: vomiting, urinating less often than normal, dizziness, and headache. They tell patients to report these right away.

The SUPREP and CLENPIQ guides go further. They tell patients to contact a provider right away for severe vomiting, confusion, delirium, fainting, or seizures. The SUTAB guide adds abnormal heartbeats to that list.

MedlinePlus separates mild from severe dehydration. Mild to moderate signs include thirst, a dry or sticky mouth, darker yellow urine, and headache. Severe signs include not urinating, very dark or amber urine, confusion, dizziness, and a rapid heartbeat. MedlinePlus says to call 911 if the person loses consciousness or shows confusion or seizures.

If you only feel queasy but you are still passing urine and staying alert, a call to the unit is usually enough. If you faint, become confused, or have a seizure, treat it as an emergency.

Who is more likely to vomit during prep?

Volume plays a role. The Task Force review notes that high-volume regimens caused more nausea than low-volume ones in the trials it cited. It also suggests that a 2 L regimen may be enough for most people. If a 4 L prep made you vomit before, ask about a lower-volume option next time.

People with swallowing problems carry a separate risk. The labels for GoLYTELY, SUPREP, PLENVU, and CLENPIQ warn that patients with an impaired gag reflex are at risk for regurgitation or aspiration of the solution. They advise observation during dosing.

GLP-1 drugs are another factor. The multisociety guidance on GLP-1 receptor agonists, first published in late 2024, notes that these drugs slow gastric emptying and commonly cause nausea and vomiting. It flags the dose escalation phase, higher doses, and weekly dosing as raising the risk of delayed emptying. The Task Force adds that these drugs may affect when you should stop drinking the prep. For more on the drugs themselves, see glp1.md. Our guide to medications to stop before a colonoscopy covers what to ask your prescriber.

What happens if vomiting leaves your prep inadequate?

You may still get your colonoscopy. The endoscopist judges prep quality during the exam, after washing and suctioning the colon. Some units can also give enemas and complete the exam later that day. The Task Force reports rescue enema success rates from 53% to 100%.

If the view is still too poor, the Task Force recommends repeating the colonoscopy within 12 months for screening or surveillance. After a positive stool-based test, it recommends repeating the exam as soon as possible, generally within 3 months.

The stakes are real. One study cited by the Task Force found a 42% adenoma miss rate at the first exam among patients who had come back after an inadequate prep. For a repeat, the Task Force recommends changes such as clearer instructions and more patient navigation. Our page on what happens after an incomplete colonoscopy explains the next steps.

The bottom line

Throwing up once during prep is common and usually manageable. Pause, rinse, sit upright, and restart more slowly, as the labels describe. Call your endoscopy unit if you cannot keep the solution down, vomit repeatedly, or may not finish on schedule. Get emergency care for fainting, confusion, or seizures. If the prep falls short, the Task Force recommends a repeat within 12 months, so a phone call now is worth making.

Last updated: September 2026. This article is for informational purposes only and does not constitute medical advice. Follow the written bowel prep instructions from your own endoscopy unit, and call that unit if you vomit and cannot keep the prep down.