sickSick Day Plan

Dosing While Sick

The default answer is to keep your weekly injection on schedule — the long half-life means missing a dose barely changes drug levels. The exceptions are when you're already vomiting, severely dehydrated, or losing fluid faster than you can replace it.

The short answer

If you have a typical cold, mild flu, sore throat, or upper respiratory infection without significant GI symptoms, take your GLP-1 on schedule. The medication's long half-life (about a week for semaglutide and tirzepatide) means skipping causes minimal drug-level change, but rejoining the schedule later can require restart-like titration if you're off too long. The cases where you should skip — or at least call your provider — are persistent vomiting, severe diarrhea, signs of dehydration, or any illness severe enough to put you in urgent care.

What to know

Weekly GLP-1s build a steady blood level that doesn't fluctuate much dose-to-dose. The whole point of weekly dosing is to smooth out the curve. Missing a single dose for a non-GI illness is mostly a no-op for the medication itself — you might feel a slight bump in appetite by day 5-6 if you're at lower doses, but at maintenance doses many people don't notice. The bigger issue is that the labels (Wegovy, Mounjaro, Zepbound) recommend resuming as soon as possible if you miss a dose, and if more than ~2 days have passed since the scheduled day, skipping that week and resuming on the regular schedule.

The trouble starts when the illness involves the GI tract. Norovirus, stomach flu, food poisoning, COVID with GI symptoms, or any condition causing repeated vomiting or diarrhea creates a double-whammy on a GLP-1: the medication is already slowing your gut and reducing appetite, and now you're losing fluid and electrolytes fast. Continuing your dose during a stomach flu can deepen dehydration and make symptoms harder to recover from. Skipping that week's dose, focusing on electrolyte fluids, and resuming once you're stable is usually the right call.

The other special case is fever and reduced oral intake. If you can't keep fluids down for 24 hours, you're dizzy when standing, your urine is dark, or you're showing other dehydration signs, the GLP-1 dose isn't the immediate problem but it's worth holding while you address the bigger issue. Call your provider for direction.

The sick day decision tree

thermostat

Mild cold, flu, sore throat

Take your dose on schedule. Stay hydrated. The illness is unrelated to the medication and missing a dose doesn't help recovery.

warning

Vomiting, diarrhea, stomach flu

Skip this week's dose. Focus on electrolyte fluids (Liquid IV, Pedialyte, broth). Resume normally next week once symptoms are gone.

phone

Severe illness or hospitalization

Call your prescriber. Anytime you can't keep fluids down for 24 hours, are dizzy standing, or need urgent care, the GLP-1 dose needs medical input.

Common questions

Common Concerns

If I skip one dose for a stomach bug, do I have to re-titrate?expand_more

No, not for a single missed dose. The Wegovy and Mounjaro labels say to take a missed dose within 5 days of the scheduled day; if more than that has passed, skip and resume next week at your current dose. Re-titration is only needed if you've been off the medication for several weeks or longer.

Will the medication make my stomach flu worse?expand_more

It can prolong recovery. GLP-1s slow gastric emptying, which is the opposite of what you want when you're trying to clear out an irritated GI tract. Pausing for the week of acute illness often makes recovery faster and more comfortable.

What about COVID — should I keep injecting?expand_more

If your COVID symptoms are mostly respiratory (cough, congestion, fatigue, mild fever), continue your dose. If you have significant nausea, vomiting, or diarrhea — which some COVID variants cause — treat it like a stomach bug and consider pausing for the week. Stay hydrated either way.

Should I skip my dose before a vaccine or infusion?expand_more

No. There's no documented interaction between GLP-1 medications and vaccines or routine infusions. Get your shot, take your dose on schedule. If the vaccine causes a rough 24-48 hour reaction, that's just the immune response, not a drug interaction.

How long can I be off before I need to restart from a lower dose?expand_more

Most prescribers consider 4-6 weeks off as the threshold for re-titration to avoid re-exposing you to early-titration nausea. Shorter gaps — including 1-3 weeks off for illness or vacation — can typically resume at your previous dose. Always confirm with your prescriber, especially if you were near max dose.

Keep exploring

Browse all GLP-1 guides.