A stomach bug arrives, or an operation gets scheduled, and the question is immediate: do I take this week's dose? Wegovy, Ozempic, Zepbound and Mounjaro are all silent on it. None of them contains a sick-day protocol.
What does exist is two things. Anaesthesiologists published guidance on GLP-1s before surgery in June 2023, and a broader group of societies revised it in multi-society guidance led by Kindel and colleagues, published in Surgical Endoscopy in 2025. And every one of those four labels warns about kidney injury when someone becomes depleted of fluid. Between them you can reason your way to an answer, and it hinges on one question more than any other: can you keep fluids down?
What to do, by situation
| What is happening | What to do | Why |
|---|---|---|
| Vomiting, or fluids will not stay down | Hold the next dose. Go back to it once you have managed fluids by mouth for a full day. | Being dry while taking something that slows the stomach is the combination behind the kidney-injury warnings on every one of these labels. |
| A cold, no stomach symptoms | Carry on as normal. | Nothing here is costing you fluid. |
| Fever, but eating and drinking fine | Carry on, and drink more than you think you need. | Fever costs water quietly. |
| Surgery under general anesthetic, higher risk — still climbing the ladder, on a weekly drug, on a high dose, or having gut symptoms | Hold a day for a daily drug, a full week for a weekly one. The later guidance adds a day of clear liquids beforehand for higher-risk patients who do continue. | These drugs slow the stomach, and food still sitting there can come back up during anesthesia. |
| Surgery, lower risk — settled on maintenance, no gut symptoms | Continuing may be reasonable. Your anesthetist decides, not this page. | The retained-food signal that prompted the original blanket hold was not seen the same way in stable maintenance use. |
| Endoscopy or colonoscopy | Raise a hold with the gastroenterology team, particularly if you will be fasting less than 18 hours. | Scopes have found food still in the stomach despite normal fasting. |
| Dental work or a minor procedure, no anesthetic, no fasting | Carry on. | No anesthetic and no empty-stomach requirement means nothing to aspirate. |
| Seriously unwell, or admitted to hospital | Hold until the team looking after you says otherwise. | These become day-by-day decisions that nobody can make remotely. |
| Pregnant, or trying to be | Stop. Wegovy's label asks for two months' clearance before a planned pregnancy. | The drug lingers, animal data show harm, and there is no benefit to losing weight during a pregnancy. |
Things worth knowing before you decide
- Dehydration is the acute danger, not the illness. All four labels record kidney injury in people who were vomiting, had diarrhea, or simply stopped drinking enough.
- A new dose step can impersonate a virus. Nausea from an increase tends to arrive one to three days after the injection and has no fever behind it. A bug usually comes with a temperature, or with someone else in the house having had it first.
- Holding a weekly drug is not an off switch. Semaglutide hangs about for roughly seven days and tirzepatide for roughly five, so the slowed stomach persists well past the dose you skipped. This matters most before surgery.
- Missing one weekly dose is rarely a problem. It only becomes a real question once the gap runs past a fortnight.
- Daily drugs are easier to pause. Liraglutide clears the one-day preoperative window on its own; a weekly drug needs seven.
Coming back after a long pause
All four labels say that once two consecutive weekly doses have gone by, your prescriber should reassess, and may bring you down a step before climbing again. In practice clinics tend to settle around this:
- A week off: usually resume where you were.
- Two to three weeks: often a single step down.
- Over a month: commonly back to the lowest dose and up again, because your tolerance for the gut effects fades much faster than the drug's effect on your weight.
Message your prescriber rather than working it out at the kitchen table. This is the one part of the page where guessing costs you a fortnight of nausea.
Symptoms that mean call today
- Severe abdominal pain that persists, especially reaching through to the back. Pancreatitis.
- A day of vomiting with nothing staying down. This is the kidney-injury scenario.
- Dark urine, dizziness on standing, barely passing water. You are already dry.
- Pain under the right ribs with fever or yellowing. Gallbladder.
- Vomit that looks like coffee grounds, or black tarry stools. Uncommon, and needs looking at the same day.
- Breathlessness, a racing heart, or confusion. Not something to ride out at home.
Outside this page's scope
This is an outpatient decision framework and nothing more. Diabetes sick-day rules — adjusting insulin, holding a sulfonylurea, checking ketones — are a separate and more urgent discipline. So are protocols for children, management of anyone already in hospital, and how antiemetics interact with all of it. Those belong to the team in front of you.
Where to go next
- Every cheat sheet — the whole single-page set.
- Missed-dose guide — each drug's window worked through, since they differ.
- Wegovy dose ladder — the schedule a hold eventually maps back onto.
- GLP-1s, pregnancy and conception — the row in the table above, at proper length.