Forgot to Take Mounjaro: what to do next

Step 1: work out where you are in the week

The first thing to do when you realise you forgot to take your Mounjaro dose is check the date. Count forward to your next scheduled injection day. If there are four or more days between now and that day, you can take the missed dose immediately. Your new weekly schedule then shifts to match whichever day you injected, so if you normally inject on a Monday but you take the missed dose on a Thursday, Thursday becomes your new day going forward.

If fewer than four days remain before your next dose is due, leave it. Take your next dose on the scheduled day as planned and carry on. It feels counterintuitive to skip it entirely, but that four-day gap exists to protect you from a surge of the medicine that your body has not had time to adjust to. Two doses in quick succession are more likely to cause nausea and other gastrointestinal discomfort than the medicine does at its usual pace.

One misconception worth letting go of: many people assume that missing a dose means their progress is lost, or that they need to go back to the start. That is not how tirzepatide works. A single missed injection does not undo weeks of treatment. Your appetite may return a little more strongly in the days around the gap, which is normal and temporary, and you can find reassurance and practical perspectives on experiences like this in our Mounjaro blogs.

Step 2: inject correctly when you do take the dose

When you take the dose (whether that is the missed one or your next scheduled one) the injection technique stays the same. Rotate your site: abdomen, thigh, or upper arm, avoiding the same spot as last time. The Mounjaro KwikPen delivers a fixed dose, so there is no adjustment needed. Store unused pens in the refrigerator at 2–8°C and check the Patient Information Leaflet for the maximum time a pen can remain at room temperature before use, since that window is specific to the product and worth confirming directly from the leaflet rather than from memory.

If you find you are regularly forgetting to take Mounjaro, it is worth linking the injection to a fixed weekly habit, a specific morning, a recurring diary reminder, the same day your bin goes out. Consistency matters less for the exact hour than for the day of the week. A useful overview of timing considerations can be found on our guide to when to take Mounjaro, which covers the best time of day and how to pick a day that works with your routine.

Some people also find it helpful to read through the full guidance on how to take Mounjaro periodically, especially when moving to a new dose strength, to make sure injection habits have not drifted.

Step 3: know when to contact your prescriber

A single forgotten dose is rarely a clinical issue. But there are situations where a conversation with your prescriber is sensible. If you have missed several doses in a row (particularly if it has happened because of side effects making you reluctant to inject) that is worth raising. Side effects at a given dose strength can sometimes be managed by slowing the titration, and your prescriber can advise on that. Pushing through significant discomfort without telling anyone is not the intended approach.

If you have missed doses because the medicine has been unavailable, that is a different situation again. Supply has been variable at points since Mounjaro launched. The cost and availability landscape has shifted since Eli Lilly adjusted UK list pricing in September 2025, and it is worth understanding what affects supply when you are planning ahead. Your prescriber or pharmacist can advise on whether a pause in treatment requires any change to your plan.

There is also a difference between forgetting a dose and deciding not to take it because of a new medication, a planned procedure, or a change in health. Those situations call for a clinical conversation before you make a decision rather than after. You can read about circumstances where pausing or skipping is genuinely advised on our page covering when not to take Mounjaro. For anything that does not fit a standard scenario, speaking to our prescribers is the clearest path to an answer that is specific to you.

Tirzepatide is the active ingredient in Mounjaro, a dual GIP and GLP-1 receptor agonist that is the only medicine of its kind currently licensed for weight management in the UK. If you want a fuller picture of how it works and what the clinical evidence behind it looks like, the tirzepatide overview covers the mechanism and the trial data in detail.