Wegovy storage before use: keeping your pen effective from pharmacy to first injection

Why semaglutide is temperature-sensitive in the first place

Wegovy contains semaglutide, a GLP-1 receptor agonist. As a peptide (a short protein chain), it breaks down when exposed to conditions it was not designed for, heat accelerates this, and freezing disrupts the molecular structure in a different way. The result, in either case, is a medicine that may be weakened or ineffective while still appearing normal in the pen. The pre-filled pen gives you no visible signal that anything is wrong; the liquid looks identical whether the dose is intact or not.

This is not a theoretical concern. The manufacturers' guidance, set out in the authorised SmPC and the Patient Information Leaflet published on the eMC (the electronic Medicines Compendium), establishes the storage limits that were used during clinical testing, the conditions under which semaglutide was proven to work. If you want to understand exactly what those validated limits look like in practice, our guide to semaglutide storage temperatures covers the specific figures and what they mean for everyday handling. Storing outside those limits means using a medicine under conditions it was never validated for. For the specifics of what those limits are for Wegovy, including the precise temperature range and how long a pen may sit out once opened, our guide to Wegovy storage temperatures sets out the exact figures in plain terms; the leaflet inside your box remains the authoritative source, so always read it before you inject.

For a broader overview of how semaglutide works and what it is licensed for in the UK, the Wegovy treatment information on this site is a useful starting point.

Refrigerator position matters more than most people realise

Most household fridges are not uniformly 2–8°C throughout. The coldest spots tend to be near the freezer element (often at the back of a top shelf, or directly beneath a freezer compartment) and a pen placed there can reach or drop below 0°C without the freezer being involved at all. Freezing, even briefly, is a reason to discard the pen.

Practical placement: a middle shelf, towards the front of the fridge, away from the back wall and away from the door, is generally most stable. The fridge door experiences the most temperature fluctuation each time it is opened, so it is not a good place for your pens. Keep each pen in its original carton to protect it from light; the carton also makes it easier to find and less likely to roll into the freezer zone by accident. Our page on storing Wegovy in the fridge explains how to choose the safest spot in your specific fridge setup and what to watch out for with different fridge-freezer configurations.

If you are ordering your pen on a payday treat-yourself Monday and it will sit in the fridge for a few weeks before you start, that is fine, provided it stays within the refrigeration window and the expiry date is observed. Storage time in the fridge (before first use) is limited by the expiry date printed on the label, not by any shorter in-use clock. That in-use clock only starts once you have administered your first dose from the pen.

Questions about specific storage situations (like a fridge that runs cold, or a pen that touched the back wall overnight) are exactly the kind of thing our support team and prescribers are there to help with.

What to do if your pen has been accidentally frozen or overheated

Freezing is perhaps the most common storage mishap. It can happen if a pen is placed near the back of a fridge-freezer, or if someone stores a new delivery straight into a freezer thinking that is 'colder is safer'. If a Wegovy pen has been frozen, the SmPC guidance is clear: do not use it. Discard it appropriately (a sharps container is the right disposal route for the needle, and the pen itself should go into household waste or a returns scheme per your pharmacy's guidance) then contact your pharmacy or prescriber to discuss what happens next.

Overheating is a subtler risk. A pen left in a car on a warm day, in a checked bag in a hold on a flight, or on a sunny windowsill can exceed 30°C. The Patient Information Leaflet specifies the maximum time a pen may spend above refrigeration temperature and the maximum temperature allowed; the exact figures are in the leaflet, and they apply cumulatively, not just to a single event. If you are unsure whether a pen has been compromised, the safest course is to contact the pharmacy that dispensed it.

For questions about how storage interacts with semaglutide's chemical stability more broadly, the guidance on semaglutide injection storage covers the underlying principles in more detail.

Travelling with Wegovy before you open the pen

Travelling with an unused pen requires the same fridge conditions as at home, which means planning ahead. Insulated cool bags with ice packs (not directly touching the pen) can maintain 2–8°C for several hours. For longer journeys, a purpose-built medicine travel cooler is more reliable. Airlines typically allow insulin and similar medicines as carry-on with a letter from your prescriber; the same letter covers Wegovy. Never put a pen in checked luggage if the hold may be unheated.

If your trip spans different temperature zones or your fridge access will be unreliable, discuss this before you travel, a prescriber can advise on timing your injection to minimise the storage challenge. Our full Wegovy storage guide goes into more detail on what counts as an excursion and when a pen is still safe to use.

When you are ready to check your eligibility for Wegovy through a regulated UK online pharmacy, starting a free consultation is the appropriate next step, a GPhC-registered prescriber reviews every application personally.