Until the beyond-use date the pharmacy prints on the vial. FDA adds a second limit: discard a multi-dose vial 28 days after first use, even if the compounder’s instructions allow longer [1]. The pharmacy’s date is set under USP <797>, whose refrigerator ceilings for a sterile preparation run from 24 hours to 90 days depending on how it was made and tested [2]. No study has measured how long compounded semaglutide stays potent in a home fridge.
So the answer is on the label rather than in the literature, and the useful question is who wrote the label and on what basis. Three things decide it: the rule the pharmacy follows, the limit FDA adds once the vial is open, and what the published chemistry can and cannot support. Whether the product produces weight loss at all is a separate question, answered in whether compounded semaglutide works.
Who sets the date, and on what basis
A beyond-use date is the date, or the hour and date, after which a compounded preparation must not be used, stored or transported, counted from the time it was compounded [2]. It is set by the compounding pharmacy, not by the seller that took the order and not by the prescriber. USP describes it as the point at which the preparation is at increased risk of chemical degradation, microbial contamination and failure of its container.
The revised USP <797>, published on November 1, 2022, sorts sterile preparations into three categories [2]. Category 2 dates depend on how the preparation was made, aseptically or by terminal sterilization, and on whether it passed sterility testing. They also depend on whether any starting ingredient was nonsterile, and on storage at room temperature, in a refrigerator or in a freezer.
For an aseptically processed preparation kept in a refrigerator, USP’s fact sheet gives these ceilings [2]. Category 1 allows up to 24 hours. Category 2 made with one or more nonsterile starting components and no sterility testing allows 4 days, and made only from sterile components without testing, 10 days.
Passing a sterility test raises the Category 2 ceiling to 45 days in a refrigerator. A Category 3 preparation, which is sterility tested and meets stricter facility requirements, may be dated up to 90 days refrigerated [2]. A reader cannot tell from the vial which of those rows the pharmacy used, which is why the printed date is the figure that counts.
A ceiling based on sterility is not the only limit. A review of sterile compounding practice notes that pharmacists should assign the shorter of the sterility-based date and the date supported by the drug’s chemical stability [3]. It adds that a date longer than the sterility-based limit requires sterility testing under USP <71>. That review predates the 2022 revision and uses the older risk-level terms, but the principle carried over.
The 28-day limit once the vial is open
Compounded GLP-1 drugs may be dispensed in vials that hold several doses, which the patient draws up at home with a syringe. FDA recommends using such a vial within 28 days after first use, because the risk of contamination rises after that point [1].
FDA is specific about the conflict a reader may face. It tells consumers to discard the vial at 28 days even if medication remains, and not to keep using it even if the compounder’s instructions say it can be used for longer [1]. It also recommends a new sterile needle and syringe for every dose. The steps of drawing a dose from a vial, and where people go wrong, are covered in whether you can mix your own semaglutide.
How often the date is published before purchase
A pharmacy has to put a beyond-use date on the vial, but a seller does not have to publish it on the product page. A review of compounding websites between February and March 2025 identified 33 compounded semaglutide or tirzepatide products that differed from the approved ones [4].
Only 18% of them reported information about a beyond-use date and preferred storage conditions, and 28% reported preferred storage conditions [4]. For most products, then, the storage life is something a buyer learns when the vial arrives rather than before paying. The same review is the source for the added ingredients discussed in why compounded semaglutide is mixed with B12.
What the chemistry shows, and what it does not
Semaglutide is a peptide, and peptides break down during formulation, storage and transport. A preformulation study held semaglutide in solution at 25 °C, 40 °C and 60 °C for 28 days and at 80 °C for 7 days [6]. Degradation produced 13 known impurities, and pH was a key factor in how quickly heat degraded the peptide.
A laboratory comparison found significant differences in strength, total impurities and high-molecular-weight protein between compounded semaglutide and the originator product when both were exposed to light [5]. The authors wrote that the distinct impurity profiles could be affected by degradation during storage, among other factors. They are current or former Novo Nordisk employees, and Novo Nordisk makes the originator; the study is described in the manufacturer’s impurity testing of compounded copies.
Neither study measured a vial in a refrigerator at 2 °C to 8 °C over the weeks a patient uses it. They show that heat, light and pH matter to semaglutide, which is the reason for refrigeration and a dated label, but they do not supply a shelf life for any compounded product.
How the branded pens compare
The comparison helps with the related question of whether semaglutide expires. An unopened Ozempic pen is kept in a refrigerator at 2 °C to 8 °C until the expiration date on the carton [7]. After first use, the label allows 56 days at room temperature up to 30 °C or in a refrigerator.
Those figures come from the manufacturer’s stability testing of its own product, and they do not transfer to a compounded vial made from a different formulation. What does transfer is the habit: keep the product cold, keep it out of light, and read the date the maker printed. The wider safety picture for compounded products, including dosing errors, is in whether compounded semaglutide is safe.