Missed Your Mounjaro Dose for a Full Week? Here's What Matters

What should you do the moment you realise you've missed a week's dose?

The short answer: inject as soon as you remember, then return to your original day the following week. Mounjaro's Patient Information Leaflet, available in full on the electronic Medicines Compendium, is explicit that a missed dose can be taken up to four days (96 hours) before your next scheduled injection. If fewer than four days remain before that next dose is due, skip the missed one entirely and pick up the usual schedule from there.

The rule against doubling up is firm. Two doses of tirzepatide in quick succession significantly raises the risk of nausea, vomiting and other gastrointestinal symptoms without any additional benefit. One dose, on time or as close to it as you can manage, is always the right call.

A practical note: many people keep their pen in the fridge door, which makes it visible every morning. If yours has been sitting there untouched since last week, that's your prompt. Inject it today, mark the new day on your phone, and you're back on track. Our broader guide to missed Mounjaro doses covers the full decision tree if you're unsure which situation applies to you.

Does a one-week gap change how the medicine works in your body?

Tirzepatide has a half-life of roughly five days, which means meaningful amounts of it remain active in your system for several days after a missed injection. A single skipped week will reduce circulating levels, but it won't undo weeks of treatment. Most people find their appetite returns somewhat during the gap, which can feel unsettling, but it reflects the medicine's mechanism rather than any lasting setback.

When you restart, the medicine's effect on gastric emptying and appetite signalling rebuilds over a few days. The NHS tirzepatide medicines page notes that gastrointestinal side effects are most common when starting treatment or after a dose change; the same can apply after a break, so eating smaller portions for the first day or two back is sensible.

Your weight-loss trajectory after a single missed week is unlikely to be materially affected. Consistency over months matters far more than one lost injection. If you're curious about what the evidence shows for tirzepatide at maintenance doses, that page sets out the trial results in full.

When does a missed week tip into territory that needs prescriber input?

One week is generally manageable without clinical escalation, provided you resume promptly. The picture shifts when a gap stretches to two or more weeks, or when you're unsure whether you're within the four-day window. For gaps approaching or beyond two weeks, your prescriber may advise restarting at a lower dose to reduce the risk of side effects — a sensible precaution rather than a step backwards. You can read about what to do after missing two weeks of Mounjaro if your situation has gone further than a week.

Other moments that warrant a call to your prescriber: if nausea, vomiting or diarrhoea after restarting is severe enough to prevent you eating or drinking; if you experience sustained abdominal pain, particularly pain that spreads to your back (a symptom worth taking seriously, given the MHRA's Drug Safety Update guidance on GLP-1 medicines and pancreatitis); or if you've had a change in health circumstances since your last dose.

If you're already thinking about longer gaps or a full restart, those pages address the steps involved. And if a recurring issue with your supply is causing gaps, understanding the current UK pricing landscape may help you plan ahead. For anything clinical, our prescribers are reachable seven days a week through the contact page.

Are there any side effects to expect when you pick up where you left off?

Yes, sometimes. After a week off, your system has had a short rest from the medicine's effects on gastric emptying, and reintroducing it can briefly reproduce the early-treatment pattern of mild nausea or loose stools. This is not a sign that something has gone wrong; it's a physiological reset.

Practical steps that help: eat light, protein-forward meals for the first day or two back; stay well-hydrated; avoid fatty or very spicy foods on restart day. Side effects from a single missed week tend to be milder and shorter-lived than those people experience when first starting treatment.

If you've been concerned about side effects at higher doses, the restart principle is the same regardless of which strength you're on: resume your current dose unless your prescriber has specifically advised otherwise. There's no clinical rationale for stepping back to a lower dose after one missed week alone.

If you'd like to discuss your treatment plan or have questions about your current dose, check your eligibility and speak to our clinical team, a GPhC-registered prescriber, not a chatbot, will review your consultation the same day.