How Long Reconstituted Semaglutide Lasts in the Fridge — and Why It Matters

Step 1, understand what 'reconstituted' means for semaglutide storage

The word 'reconstituted' points to a specific preparation step: combining a powdered or lyophilised form of semaglutide with a sterile liquid diluent before use. This is distinct from the pre-filled Wegovy injection pens, which arrive from the pharmacy ready to use and do not require mixing. Reconstituted semaglutide is most commonly encountered with compounded or research-grade preparations, which sit outside the licensed UK supply chain.

This distinction matters for storage. Licensed Wegovy pens contain semaglutide in a stable, pre-formulated solution; the manufacturer's stability testing underpins the shelf-life data printed on the packaging. A reconstituted preparation has its own, usually shorter, stability window because once the powder is dissolved the degradation clock starts at a different rate. A question our prescribers hear most weeks is whether a pen left out overnight is still safe, and if you want to understand how long semaglutide will last in the fridge depending on which preparation you have, the honest answer is: check the leaflet, because the licensed product and a compounded reconstituted version follow different rules.

For licensed Wegovy pens, the NHS semaglutide information page and the product's Patient Information Leaflet are the primary references for storage. For compounded or unlicensed reconstituted semaglutide, the MHRA has warned clearly that products sourced outside the licensed supply chain may be substandard or fake, and no reliable shelf-life data exists for them.

Step 2, follow the fridge rules for the product you actually have

Licensed pre-filled semaglutide pens (Wegovy) should be stored in the fridge between 2°C and 8°C before first use. The SmPC and Patient Information Leaflet specify a limited room-temperature window for the original sealed pen, but that allowance does not extend indefinitely, and once a pen has been started it should return to the fridge after each injection. It must not be frozen; a pen exposed to freezing temperatures should be discarded rather than used.

For a reconstituted preparation, the stability is typically shorter and more sensitive to temperature fluctuation. Without the manufacturer's validated stability data, the safest working assumption is that the window is no more than a few weeks at 2–8°C, but the only figure you should act on is the one in the specific product's documentation. Using a preparation past its stated date, or one that has been stored outside the recommended range, risks both reduced effectiveness and, in the case of unlicensed compounded products, genuine safety concerns.

If you are on licensed Wegovy and want to understand how long Wegovy pens last in the fridge in practical terms, the leaflet in your box is the definitive source. The eMC listing for Wegovy also carries the full, up-to-date storage section of the SmPC.

Step 3, recognise when to discard and what to do next

Semaglutide solution should be clear and colourless to slightly yellow. If the liquid looks cloudy, contains visible particles or has changed colour, do not use it. The same applies if the pen has been dropped and may have been damaged, if it has been frozen, or if the expiry date has passed.

Discarding a pen that costs money is frustrating. The question most people then have is whether they can skip a dose or double up the next one. Neither is the right approach, your prescriber should be contacted so they can advise on timing, and your dosing schedule should be adjusted only on clinical guidance. Details about how long a semaglutide pen lasts in normal use may also be useful if you are planning ahead around travel or deliveries.

Used pens and needles must be disposed of safely in an approved sharps container, never in household waste. If you need one, a 1-litre sharps container is available through our pharmacy. The MHRA's Yellow Card scheme allows you to report any suspected issues with your medicine, including concerns about product quality or adverse reactions.

A word on unlicensed reconstituted semaglutide in the UK

There is a practical reason this keyword comes up: some online sellers market reconstituted semaglutide powders or vials as a cheaper alternative to licensed Wegovy pens. These products are not approved by the MHRA for use in the UK, and the MHRA has issued repeated warnings about fake and substandard injectable weight-loss products seized in large quantities from unlicensed sources. Without a manufacturer's validated shelf-life study, any storage guidance attached to these products is unverified.

Licensed Wegovy, supplied through a GPhC-registered pharmacy on a valid prescription, carries fully verified storage data because it has been through the regulatory process that requires exactly that evidence. If you are considering semaglutide for weight management and want to understand what Wegovy treatment involves through a regulated route, our prescribers can talk through whether it is clinically appropriate for you. The ingredients and formulation of the semaglutide injection also affect how it should be stored, which is another reason the licensed product and a compounded version should not be treated interchangeably. For cost context on accessing semaglutide through a legitimate private route, the Wegovy pricing guide explains what a lawful prescription typically includes.