Wegovy shelf life after opening: what the guidance actually says

What the SmPC tells us about in-use storage windows

The Wegovy SmPC, published on the eMC, sets the in-use period at a maximum of six weeks at room temperature, defined as below 30°C. That clock starts the moment you take the pen out of the fridge for the first time, not the moment you press the button for your first injection. So if you refrigerate and then remove a pen, let it warm up, decide to delay your dose and return it to the fridge, the six-week countdown has already begun. The date of first removal is the one that matters, and our guide to Wegovy shelf life explains how to track that window across your whole course of treatment.

Before opening (meaning before you have ever used that pen) Wegovy must be kept refrigerated between 2°C and 8°C. Many people keep their spare pens in the fridge door, which is convenient, but that spot can be warmer than the main shelf. A thermometer costs a few pounds and removes any doubt. The NHS medicines page for semaglutide echoes this storage guidance and advises patients to read the leaflet that comes with their pen.

One practical note our prescribers pass on: write the removal date on the label in pencil when you first take the pen out. It takes five seconds and saves a lot of mental arithmetic six weeks later.

Why the six-week limit exists and what happens beyond it

Semaglutide is a peptide medicine. Peptides are sensitive to temperature swings and, to a lesser extent, light. The six-week room-temperature window is the period over which Novo Nordisk's stability data demonstrates that the medicine retains potency and sterility within licensed parameters. After that point, the manufacturer cannot guarantee either, which is why using an out-of-window pen is not a minor technicality. You might be injecting a less effective dose, or a solution that has begun to degrade.

The visual checks matter too. Before every injection, inspect the solution: it should be clear and colourless to slightly yellow. Any cloudiness, particles or discolouration is a signal to stop, not to proceed. Wegovy pens should also never be frozen, ice formation damages the solution irreversibly, and a pen that has frozen is not recoverable even if it looks fine once thawed.

For a full picture of how the unopened shelf life compares, the page on semaglutide shelf life unopened covers what to expect from pens still in the fridge and how expiry dates work before a pen has been used.

Travelling and the in-use pen: keeping within the rules

A pen that is already in use travels more easily than an unopened one, because it does not need refrigeration for up to six weeks at below 30°C. That said, a gym bag left in a car on a summer afternoon can easily reach 40°C or more (above the 30°C limit) so travel cases with insulation are worth using even for in-use pens.

For flight travel, an in-use pen can typically go in hand luggage (the liquid-allowance rules for prescribed medicines differ from general liquids; carry your prescription or dispensing label). An unopened pen going into the hold needs adequate cold protection. The detail on longer journeys is covered on the page about semaglutide shelf life once opened, which addresses multi-stop scenarios and what to do if your cooling method fails.

If you are ever uncertain whether an in-use pen is still within its window, the safest course is to contact your prescriber or pharmacist rather than estimate. Using a pen outside its storage parameters is the sort of thing that is worth a quick message to avoid.

What to do at six weeks: the question about using a pen beyond its in-use window

The licensed answer is clear: a pen that has been out of the fridge or in use for more than six weeks should not be used. Some patients ask whether there is any leeway, the honest answer is that the SmPC does not provide one. The six-week figure is the tested, authorised limit. Using the pen beyond it is outside the licensed conditions, meaning you are not using the medicine as it was approved.

This is a question our prescribers see fairly often, usually because someone has been unwell and missed a dose, or because life got in the way for a week or two. If that has happened to you, the practical next step is to discuss it directly with your prescriber rather than guess. The page on whether Wegovy can be used after six weeks of opening goes into the clinical nuance in more detail.

More broadly, questions about what happens when treatment pauses, restarts or ends are covered in the guide to life after Wegovy, which looks at what clinical evidence says about maintaining weight after stopping treatment. And if you are weighing up how Wegovy fits into your overall options, the Wegovy overview and the weight-loss treatments page set out the full picture.

Wegovy is a prescription-only medicine. If you are considering starting treatment, start your free consultation with our prescribers, who review every application the same day.