Storing lyophilised semaglutide correctly: a practical guide

Step 1, Keep unopened pens refrigerated until you need them

The starting point for safe storage is the fridge. Unopened Wegovy pens should sit at 2–8 °C, away from the freezer compartment and not pressed against the back wall where temperatures can dip below zero. Freezing denatures the semaglutide molecule, and a frozen pen cannot simply be thawed and used as normal. If you are unsure whether your pen has been frozen, the Mounjaro and Wegovy SmPCs on the eMC both describe what discolouration or cloudiness to look for, and the answer in either case is: do not inject it.

In practice, the fridge door is one of the warmer spots and keeps pens away from accidental freezing. Some people use a dedicated drawer or the middle shelf. What matters is consistency, not perfection of placement. If you travel or lose power for a period, our Wegovy storage guidance covers what to do when conditions change.

For context on how temperature rules apply across the semaglutide range more broadly, including devices such as the skinny pen semaglutide format, the semaglutide storage temperature page explains the relevant tolerances in detail.

Step 2, Understand the room-temperature window before you inject

Once a Wegovy pen has been removed from the fridge, the clock starts. The Patient Information Leaflet specifies a maximum time at room temperature; we do not reproduce that figure here because it applies to the licensed product in its current formulation, and Novo Nordisk may update it. Always check your leaflet. What we can say clearly: that window exists, it is finite, and once it has passed the pen should not be returned to the fridge and used later as though nothing happened.

A question our prescribers hear most weeks is whether a pen that was accidentally left out overnight is still usable. The honest answer is: refer to the leaflet first, then contact our pharmacy team or your prescriber if the time elapsed falls outside the stated limit. Guessing is the wrong move with a peptide medicine. For a precise breakdown of what the licensed guidance actually says, see the Wegovy storage temperature page.

Injecting at room temperature is more comfortable than injecting a cold pen. Taking it out 15–30 minutes before your dose is fine, provided it goes back in the sharps bin promptly after, not back into the fridge.

Step 3, Reconstituted semaglutide and lyophilised forms: what changes

Lyophilisation removes water from a biological medicine to extend shelf stability during storage and transport. Once the powder is reconstituted with a diluent (which is the step that produces an injectable solution) the stability window shortens considerably. This is why healthcare settings that use reconstituted peptide preparations treat reconstituted product as time-limited and temperature-controlled, typically requiring refrigeration and use within hours or days, not weeks.

For patients using the licensed Wegovy pre-filled pen, this reconstitution step happened at the manufacturing stage; your pen arrives as a ready-to-use liquid. But understanding the lyophilisation principle matters if you encounter discussions of compounded or unlicensed preparations. The MHRA's Yellow Card reporting scheme is the right place to flag any concerns about the quality of medicine you have received, including unexpected appearance or suspected temperature breach.

For everything related to how semaglutide injections are used and stored day to day, our semaglutide injection storage guide is a useful companion to this page.

Disposal, needles and practical accessories

Correct storage ends at correct disposal. Used pens and needles are sharps and must go into a proper sharps container, not household waste. NHS guidance is clear on this, and most local councils offer sharps collection. If you need a container at home, a 1-litre sharps bin is available from our pharmacy alongside your treatment.

Needle hygiene matters too. Each injection should use a fresh needle; re-using needles blunts the tip and increases the risk of injection-site reactions. The NHS semaglutide medicines page covers this as part of the standard advice for Wegovy users.

If you are considering whether semaglutide is the right treatment for you, or want to understand how our prescribers assess clinical suitability, our Wegovy overview is a good place to start. And if you are ready to take the next step, you can check your eligibility through a free consultation with our GPhC-registered prescribers.