Using Your Wegovy Pen After 30 Days: What the Guidance Actually Says

What the SmPC and NHS guidance actually say about the 28-day limit

The confusion around "30 days" is understandable. Many medicines come with a monthly supply framing, and Wegovy's dosing schedule is monthly in practice. But the licensed storage guidance, set out in the Wegovy SmPC and summarised on the NHS semaglutide medicines page, is clear: once a pen has been taken out of refrigeration, it must be used or discarded within 28 days. That is the outer limit.

The reasoning is pharmacological stability. Semaglutide degrades at room temperature over time. Novo Nordisk ran the stability testing that underpins this figure; it is not a conservative guess. Going two days past the window (or even one) puts you outside the conditions under which the medicine's effectiveness and safety were demonstrated.

This applies to every strength in the Wegovy titration schedule: 0.25 mg, 0.5 mg, 1.0 mg, 1.7 mg and 2.4 mg pens all share the same 28-day room-temperature rule. The newer 7.2 mg single-dose pen, approved by the MHRA in April 2026, carries the same class of instruction, always check the leaflet supplied with your specific pen.

If you have ever wondered exactly whether semaglutide expires after 28 days, the short answer is yes, and if your pen has been sitting at room temperature since before your last injection and more than 28 days have passed, it needs to go.

Why this matters more than it might seem

A pen past its room-temperature window is not obviously wrong. It looks identical to a fresh one. There is no colour change, no smell, no visible sign that the medication has degraded. That is precisely why the written guidance matters: you cannot assess it by eye.

Using degraded semaglutide is unlikely to cause acute harm in the way a contaminated product might, but it can mean your dose is less effective than expected, which matters on a medicine where consistent weekly administration underpins the weight-loss results seen in the STEP 1 clinical trial, published in the New England Journal of Medicine. That trial showed an average weight reduction of around 15% at 68 weeks in adults taking semaglutide 2.4 mg weekly alongside lifestyle support. Consistent dosing is part of what produces that kind of outcome.

There is also a practical knock-on. If you inject a degraded pen and notice less appetite suppression than usual, the instinct can be to query your dose rather than your storage. Ruling out a storage issue first keeps your prescriber's picture accurate.

For a broader look at how storage conditions affect your pens day to day, the guide to storing Wegovy after first use covers fridge placement, travel, and what happens if the pen freezes.

What to do with a pen that has passed the 28-day mark

Do not inject it. The next step is disposal, and the right way to do that matters too. Used or expired Wegovy pens are considered sharps waste; they should not go in a household bin. Your local council or pharmacy will have a sharps disposal route, a sharps container is the correct receptacle, and most community pharmacies in the UK will accept filled containers for safe disposal.

Once the pen is safely dealt with, contact your prescriber or pharmacy to arrange a replacement as soon as possible. Missing a weekly dose is not ideal, but it happens. Your prescriber can advise on whether to continue with your current dose schedule or adjust timing. The Patient Information Leaflet has a missed-dose section; for personalised guidance, your prescriber is the right person to speak to, not the leaflet alone.

If you are managing costs and wondering how to avoid wasted pens, our Wegovy price comparison page covers what a private prescription typically includes and what to look for when choosing a provider.

Keeping track so this does not happen again

The simplest fix is a note in your phone on the day the pen leaves the fridge. Set a reminder for day 26 or 27, two days before the window closes. That gives you time to check whether the pen has been used as planned and to flag anything to your prescriber before the deadline. Some people do this the same way they remember their weekly injection day: pick a consistent time, perhaps a Sunday morning before the week gets busy, and do both checks at once.

Keeping pens in the fridge at 2–8°C until the day you need them is the most reliable approach for anyone on a regular weekly schedule. The fridge door is fine as long as it is not touching the freezer section. Our page on how to use the Wegovy pen walks through the full injection process, including how to prepare the pen correctly each time. And if you have ever found the mechanism stiff or unresponsive, the troubleshooting guide for a stuck Wegovy pen covers the most common causes.

After each injection, the used pen needs to be disposed of safely rather than recapped and kept. For the full picture on what happens to pens once you have finished with them, see the guidance on what to do with Wegovy pens after use.

If you are considering starting Wegovy or are due a clinical review of your current treatment, our team reviews consultations the same working day. Speak to our prescribers to get a clinical assessment from a GPhC-registered Independent Prescriber.