How long reconstituted semaglutide lasts in the fridge
The pens have exact numbers on the label. A vial you mixed yourself, or one a pharmacy prepared, does not, because it is not an approved form. Here is what each source of guidance actually says.
The short answer is that there is no single number. For the approved pens, the label gives exact figures. For a compounded vial, the number that applies is the beyond-use date the pharmacy printed on it. For a powder vial that you reconstitute yourself, no official figure exists at all, and anyone who gives you one is generalising. This page goes through each case.
What the labels say about the pens
Ozempic and Wegovy are sterile, clear, colourless solutions in sealed pens. The prescribing information sets out storage like this:
| Product | Before first use | After first use or out of the fridge |
|---|---|---|
| Ozempic pen (multiple weekly doses) | Refrigerator, 2 to 8°C, until the expiry date | 56 days, at 15 to 30°C or in the refrigerator |
| Ozempic single-dose prefilled syringe | Refrigerator, 2 to 8°C | If needed, up to 28 days at 8 to 30°C; discard after use |
| Wegovy single-dose pen or syringe | Refrigerator, 2 to 8°C, in the original carton | If needed, before the cap is removed, up to 28 days at 8 to 30°C; discard after use |
| Wegovy FlexTouch pen (multiple doses) | Refrigerator, 2 to 8°C | 56 days, at 15 to 30°C or in the refrigerator |
All of them: do not freeze, do not use if frozen, keep away from the refrigerator's cooling element, and protect from light and excessive heat. The labels also say to look at the solution first: it should be clear and colourless.
Why a reconstituted vial has no label figure
A label figure comes from stability studies the manufacturer ran on that exact product, in that exact container, and submitted to the FDA. A vial of semaglutide that someone reconstituted from powder, or that a pharmacy compounded, is not that product. FDA's own page on unapproved GLP-1 drugs is direct about it: compounded versions do not go through FDA review for safety, effectiveness or quality before they are sold. So there is no FDA-reviewed stability data to quote, for the fridge or anywhere else.
Compounded vials: the beyond-use date
A compounding pharmacy assigns a beyond-use date to each preparation, under the US Pharmacopeia's chapter on sterile compounding, USP <797>. That date depends on how and where it was made, how it is stored, and whether sterility testing was done. It is printed on the label, and it is the date that applies, not a figure from the internet.
One rule in USP <797> explains where the familiar "28 days" comes from. For a multiple-dose container, the beyond-use date after the vial is first punctured is 28 days, unless the manufacturer specifies otherwise. That is a sterility convention for a preserved, multi-use container. It is about the risk of contamination from repeated needle entry. It is not a guarantee that the drug inside is still at full strength on day 28.
FDA's April 2026 statement and the end of the shortage have changed who compounds semaglutide and how much. The FDA and compounded GLP-1s page has the timeline.
Bacteriostatic water and benzyl alcohol
Powder vials are usually reconstituted with bacteriostatic water. Pfizer's label describes it as sterile water for injection containing 0.9% (9 mg/mL) or 1.1% benzyl alcohol as a bacteriostatic preservative, supplied in a multiple-dose container for repeated withdrawals. The label also says benzyl alcohol must not be used in newborns. The preservative slows the growth of bacteria introduced by repeated punctures. It does nothing to stop the peptide itself from slowly degrading in solution, which depends on the molecule, the concentration, the pH and the temperature. The bacteriostatic water entry has more.
Our peptide storage guide takes the same position for every peptide: a sealed powder and a reconstituted solution are different problems, and any single "lasts X days" figure is a generalisation across molecules that behave differently. The semaglutide reconstitution page covers the mixing itself.
Signs a vial should not be used
- The solution is cloudy, has particles, or has changed colour. The approved product is clear and colourless.
- It has been frozen, even once.
- It has been left somewhere hot, such as a car or a sunny windowsill.
- It is past the beyond-use date on the pharmacy label, or past 28 days from first puncture for a multi-dose vial with no other instruction.
- The stopper is damaged or the vial is cracked.
The harder truth is that loss of potency is usually invisible. A clear vial can still be weaker than it was. If a dose that used to bring side effects suddenly does nothing, a degraded vial is one possible reason, and it is worth raising with the prescriber before changing anything.
Practical habits
- Write the date of first puncture and the concentration on the vial.
- Store at 2 to 8°C, on a middle shelf rather than in the door or against the back wall where some fridges freeze.
- Do not freeze a solution to make it last longer.
- Use a new needle every time, and never share a vial or pen between people.
Dose errors are their own risk. FDA has received reports of adverse events, some requiring hospitalisation, that may relate to dosing errors with compounded injectable semaglutide, including patients measuring the wrong amount. Knowing the concentration in mg/mL is what turns a syringe marking into a dose.
Peptide AI tracks vials with the doses remaining, free, so the date you opened a vial and how much is left sit next to every dose you log. The free GLP-1 tracker page explains how it works.
Questions people ask
How long does reconstituted semaglutide last in the fridge?
There is no FDA figure, because a reconstituted or compounded vial is not an approved form. A compounded vial has a beyond-use date on the pharmacy label, and that is the date that applies. USP 797 sets 28 days after first puncture for multiple-dose containers unless otherwise specified.
How long does an Ozempic pen last after first use?
The label gives 56 days after first use, stored at 15 to 30 C or in the refrigerator at 2 to 8 C. Before first use, it stays in the refrigerator until the expiry date.
Can Wegovy pens be kept out of the fridge?
Single-dose Wegovy pens can be kept at 8 to 30 C for up to 28 days before the cap is removed, if needed. The multi-dose Wegovy FlexTouch pen can be used for 56 days after first use, at room temperature or in the fridge.
Why do people say peptides last 28 days once mixed?
USP 797 sets a 28-day beyond-use date for a multiple-dose container after first puncture, unless the manufacturer says otherwise. It is a sterility convention for repeated needle entry, not a measure of how long the drug stays at full strength.
How can I tell if semaglutide has gone bad?
Do not use it if it is cloudy, has particles, has changed colour, has been frozen, or is past its beyond-use date. The approved solution is clear and colourless. Loss of potency can also be invisible, so a sudden change in effect is worth raising with your prescriber.
Sources
- Ozempic prescribing information, Novo Nordisk
- Wegovy prescribing information, Novo Nordisk
- FDA's concerns with unapproved GLP-1 drugs used for weight loss, U.S. Food and Drug Administration, current as of 1 October 2026
- General chapter 797: pharmaceutical compounding, sterile preparations, United States Pharmacopeia
- Safe injection practices and USP 797 (webinar slides), Minnesota Department of Health and Minnesota Board of Pharmacy
- Bacteriostatic water for injection, USP: prescribing information, Pfizer
- FDA clarifies policies for compounders as national GLP-1 supply begins to stabilize, U.S. Food and Drug Administration, updated 1 April 2026
