Missed a Week of Mounjaro — What Happens and What to Do

Step 1, Work out exactly how long it's been

Mounjaro is injected once a week, and the licensed guidance builds in a short recovery window. Count back to the date your last injection was due, not the date you gave it. If fewer than five days have passed since the missed dose was due, you can inject it as soon as you remember, then return to your original weekly day from that point onwards. If five days or more have elapsed, leave that dose out completely.

This isn't about being strict for its own sake. Tirzepatide has a half-life that means taking a late dose too close to your next scheduled one stacks the medicine's effect. That raises the chance of a rough few days of nausea or vomiting rather than any benefit. The NHS's tirzepatide guidance covers this window clearly if you want to read the official wording alongside this.

One practical note: if you're not sure of the exact date, check the sharps bin or any tracking app you use. Getting the arithmetic right matters more than acting quickly.

Step 2, What to do (and not do) on the day you remember

This is a question our prescribers hear most weeks, and the answer is consistent: never inject two doses in a seven-day period to make up for the one you missed. Two pens' worth of tirzepatide in a week will almost certainly cause more nausea, vomiting, or diarrhoea than you'd otherwise experience, without adding meaningful benefit to the dose you were already getting.

If you're within the five-day window, take the missed dose now, using your usual injection site (abdomen, thigh, or upper arm) rotating away from wherever you last injected, and if you need a walkthrough of how to prepare and use your pen correctly, our guide on how to break the Mounjaro pen for the golden dose explains the process step by step. Then note the new date as your weekly day going forward, or return to the original day if you prefer; either approach keeps your weekly rhythm intact. What you should not do is change to a different strength to compensate. If you were on 5mg before the missed week, 5mg is what you return to.

Store any unused pens in the fridge at 2–8°C until you need them, and always check the Patient Information Leaflet for the current permitted room-temperature window before travelling.

Step 3, Expect your body to notice the gap

Many people find that resuming after even a single missed week brings back mild side effects they thought they'd moved past. Nausea, digestive discomfort, or a dip in appetite that feels sharper than usual are common. This usually settles within a few days, just as it did when treatment first started. It's not a sign that something has gone wrong, it's simply the body adjusting to the medicine's presence again after a break.

Keeping meals smaller and lower in fat during the first few days back can help considerably. Protein and hydration are worth prioritising, particularly if you find your appetite drops sharply on re-starting. There's a broader look at managing Mounjaro and day-to-day life on the Mounjaro overview page, which covers what to expect across the treatment course.

If side effects after resuming feel severe rather than just uncomfortable (persistent vomiting you can't keep fluids down through, or severe stomach pain that reaches your back) contact a healthcare professional promptly. The MHRA's Yellow Card scheme exists so that patients can report unexpected or serious reactions directly.

If you've been off Mounjaro for more than a week or two

A gap of three or more weeks is a different situation. At that point the medicine will have largely cleared your system, and jumping straight back to whatever dose you were on carries a higher risk of side effects. It doesn't automatically mean dropping back to 2.5mg, but it does mean a conversation with your prescriber before you resume, they'll look at how long you've been off, which dose you were at, and what's been happening with your weight and any related conditions.

You can read more about the longer gap scenario on the three-week missed dose page, which sets out what the evidence and clinical guidance suggest. For a two-week gap specifically, this page covers that ground in detail.

Cost and supply are sometimes the practical reason people miss doses. If that's a factor, our guide to UK Mounjaro pricing explains what happened to list prices in 2025 and what typical private costs look like now. It won't replace a clinical conversation, but it may help you plan. For anything about your specific treatment, our aftercare team is available seven days a week.