How long does compounded semaglutide last? Fridge, light and the 28-day rule

How long does compounded semaglutide last?

Until the beyond-use date the pharmacy printed on the vial, if it stays refrigerated, and never more than 28 days after the first needle goes in. FDA says to discard a multiple-dose vial at 28 days even if the compounder's instructions allow longer, because contamination risk rises after that point.

A compounded semaglutide vial runs on two clocks. The first is the date the pharmacy printed on the label, which applies while the vial is sealed and refrigerated. The second starts the first time a needle goes through the rubber stopper, and it is short.

FDA states the second clock plainly. On its page about unapproved GLP-1 drugs, the agency says it generally recommends that vials containing multiple doses of sterile medication be used within 28 days after the first use, because there is an increased risk of contamination after 28 days [1]. For people who have not finished a vial by then, FDA's advice is to discard it anyway, even if medication remains, and even if instructions from the compounder say it can be used for longer [1].

Why so much caution about a product a pharmacy made? Because compounded drugs are not FDA approved: the agency does not review them for safety, effectiveness or quality before they are marketed [1]. A brand-name pen comes with storage rules built on stability studies that a regulator reviewed. A compounded vial comes with whatever the pharmacy decided, and the rest of this article is about how much weight that decision can carry.

The date on the vial is a beyond-use date

A compounded vial carries a beyond-use date, set by the pharmacy that made it, not a manufacturer expiration date backed by FDA-reviewed stability studies. Many products do not state one at all: a review of compounded semaglutide and tirzepatide products sold online found only 18% reported beyond-use date and storage information.

An approved drug has an expiration date, which the manufacturer earns with stability studies on that exact product. The Ozempic label, for example, says unused pens may be used until the expiration date printed on the label, if kept in the refrigerator [4]. A compounded product instead has a beyond-use date (the date after which the pharmacy that prepared it says it should not be used). Pharmacies that prepare sterile injectables work to a standard called USP General Chapter 797, which CDC cites in its guidance on multi-dose vials [2].

CDC adds one rule worth knowing: once a multi-dose vial is opened, the beyond-use date should never exceed the manufacturer's original expiration date [2]. In other words, the later of two dates never wins. When a label offers you a long window and a short one, the short one applies.

The bigger problem is that the date is often missing. A review published in The Annals of Pharmacotherapy searched compounding websites between February 3, 2025, and March 20, 2025 for semaglutide and tirzepatide products that differed from the approved ones. Only 18% of the products it included reported information about beyond-use date and preferred storage conditions, and 28% reported preferred storage conditions [3]. Many of those products were tablets or under-the-tongue forms rather than injectable vials, so the figure describes what sellers publish online, not what is printed on any particular vial. Still, if the label in your hand gives no date and no storage instructions, you are not the only one, and the pharmacy is the place to ask.

Does compounded semaglutide need to be refrigerated?

Yes. FDA says injectable GLP-1 drugs require refrigeration as indicated in their package inserts, and the approved semaglutide label sets that at 2°C to 8°C (36°F to 46°F) before first use, never frozen. Heat speeds the chemical breakdown of semaglutide in solution, and that loss is invisible.

FDA's answer is short: injectable GLP-1 drugs require refrigeration as indicated in their package inserts [1]. The package insert for Ozempic says that before first use the pen should be stored in a refrigerator between 2°C to 8°C (36°F to 46°F), not in the freezer or directly next to the cooling element, and not used at all if it has been frozen [4]. A compounded vial has no package insert of its own reviewed by FDA, so the approved product's rule is the sensible floor.

The chemistry explains why. Peptides (short chains of amino acids, the building blocks of proteins) break down in water through reactions such as oxidation (reaction with oxygen) and hydrolysis (water cutting the bonds that hold the chain together), and a formulation review notes that most peptide drugs need storage and transport at low temperatures, the cold chain, because of that instability [6].

Semaglutide has been tested directly. A 2025 laboratory study held semaglutide in solution under heat stress at 25 °C, 40 °C and 60 °C for 28 days, and at 80 °C for 7 days, then measured what it turned into [5]. It identified thirteen known impurities (breakdown products) and found that the acidity of the solution, its pH, was a key factor in how fast heat degraded it [5]. That study tested the raw peptide in laboratory solutions, not a compounded product, so it cannot tell you how long your vial lasts [5]. It does tell you that warmth turns semaglutide into something else, and that two solutions of the same peptide can behave differently depending on what else is in them.

Left out of the fridge, or delivered warm

No published data say how long a compounded semaglutide vial survives at room temperature. FDA advises against using any injectable GLP-1 that arrives warm or with insufficient refrigeration. The generous windows on Ozempic and Wegovy, up to 56 days in use, were measured for those pens and do not transfer to a vial.

The most common version of this question is the morning after: the vial sat on the counter overnight, or a delivery box sat on the porch all afternoon. FDA has addressed the second case. It has received complaints that certain compounded GLP-1 drugs arrived warm or with inadequate ice packs, and it recommends that patients not use any injectable GLP-1 drug that arrives warm or with insufficient refrigeration, because this can affect the drug's quality [1].

Online answers to the first case usually borrow numbers from the brand-name pens. Those numbers are real, but each one belongs to a specific product. An Ozempic pen, after first use, can be stored for 56 days at 15°C to 30°C (59°F to 86°F) or in a refrigerator [4]. An unused Wegovy pen can, if needed, be kept from 8°C to 30°C (46°F to 86°F) for up to 28 days before its cap is removed, and a Wegovy FlexTouch pen can be stored for 56 days after first use [7]. The Wegovy instructions also say to throw the pen away if it has been exposed to temperatures above 86°F (30°C) [7].

Each window was measured for one formulation in one container. A compounded vial differs in both, and sometimes in the active ingredient itself: FDA warns that some compounded semaglutide is made from salt forms such as semaglutide sodium and semaglutide acetate, which are different active ingredients from the one in the approved drugs [1]. So no room-temperature allowance carries over. What does carry over are the visual discard rules. The Ozempic label says the solution should look clear and colorless, and that a pen that looks cloudy or contains particles should not be used [4]. A vial that froze, clouded or grew particles is finished. A vial that looks normal after a warm night may still have lost strength, because chemical breakdown is usually invisible.

If the vial has to travel, keeping it cold becomes the hard part. Our guide to flying with peptides covers insulated cases, airport screening and customs.

Light degrades it too

Light is a real hazard for semaglutide in a clear vial. In a Novo Nordisk laboratory test under deliberately harsh light, the capped brand pen did not change, while two compounded vials lost strength and gained impurities. The approved labels say to keep semaglutide in its carton, so keep a vial boxed and dark.

Storage advice for compounded semaglutide almost always stops at the fridge. The approved labels do not. Ozempic's patient instructions say to keep it away from heat and out of the light and to keep the pen cap on when not in use [4], and Wegovy's say to keep the pen in its original carton to protect it from light and to throw it away if it has been exposed to light [7].

A 2026 study in Pharmaceutical Research tested what happens without that protection. The authors exposed the originator semaglutide, in its original packaging with the pen cap on, and two injectable semaglutide products in vials made by outsourcing facilities (large-scale compounders), to light under deliberately exaggerated conditions. The brand pen's concentration, impurities and clumped protein levels did not change. The compounded vials did: their strength fell from 1.01 mg/mL to 0.95 mg/mL and from 1.02 mg/mL to 0.86 mg/mL, and their total impurities climbed from 1.3% to 5.1% and from 2.5% to 14.2% [8]. The authors noted that compounded products are not necessarily sold with instructions for protecting them from light [8].

Two cautions keep this in proportion. The test used light far harsher than a kitchen, and it covered only two vials. And the authors work for Novo Nordisk, which makes Ozempic and Wegovy and competes with compounded versions. Neither caution changes the practical point, which costs nothing: keep a vial in a box or an opaque container in the fridge, not loose on a door shelf.

Why the 28-day limit is about germs, not potency

The 28-day limit is a contamination ceiling. Every needle entry is a chance to introduce bacteria, and a preservative only slows their growth. The limit says nothing about whether the semaglutide is still at full strength, which is why a vial stored warm or in light can fail long before day 28.

CDC's guidance on injection safety explains where the 28 days comes from [2]. Multi-dose vials typically contain an antimicrobial preservative to help limit the growth of bacteria, but the preservative has no effect on viruses and does not provide complete protection against bacterial contamination [2]. So once a vial is opened, it should be dated and discarded within 28 days unless the manufacturer states another date [2]. FDA adds the home version of the same logic: always use a new, sterile needle and syringe for each dose, because reusing them can contaminate the medication [1].

Contamination is not a theoretical worry with compounded GLP-1 drugs. A study of the FDA Adverse Event Reporting System (FAERS, the database where doctors, patients and companies report suspected drug problems) found 707 reports involving compounded products among 81,078 GLP-1 reports, and contamination was reported far more often for compounded products than for the rest, with a reporting odds ratio (how much more often a problem appears in one group's reports than in another's) of 19.00 [9]. Reports like these cannot give a rate, because nobody knows how many vials were used, but they point the same way as FDA's rule.

Notice what the 28 days does not promise. It is about germs, not about whether the peptide is still intact. A vial kept cold, dark and handled cleanly may be fine near the end of its four weeks, while one that spent an afternoon in a hot car may not be fine in its first week. If your product came as a powder with a separate liquid to mix in, the clock starts when you mix it, and our guide to how long reconstituted peptides last covers that case.

Check the pharmacy, then follow a simple routine

A beyond-use date is only as good as the pharmacy behind it. Use a state-licensed pharmacy, and treat a vial that arrives warm, lacks instructions or carries a suspicious label as unusable. Then refrigerate it in its box, write the first-use date on it, and discard it 28 days later.

FDA's own checklist starts before the vial is opened. It advises filling a prescription at a state-licensed pharmacy, and lists warning signs: medicine that looks different from what you received before, packaging that is broken or damaged or lacks instructions for use, spelling errors on the label, or a pharmacy name you suspect is fraudulent [1]. That last one is not hypothetical. FDA reports fraudulent compounded semaglutide whose labels name pharmacies that do not exist, or licensed pharmacies that did not make the product [1].

Even real suppliers vary. A secret-shopper study of weight-loss clinics and medical spas in West Virginia and Oklahoma, carried out from August to October 2025, traced their compounded GLP-1 products back to twenty-three compounding facilities, and 4 of the 21 it could check were not licensed to perform sterile compounding [10]. A beyond-use date printed by a facility that is not licensed to make sterile injectables tells you nothing reliable.

With a product from a pharmacy you trust, the routine is short. Refrigerate the vial at 2°C to 8°C (36°F to 46°F) as soon as it arrives, in its box or another dark container, away from the cooling element and never frozen [4]. Do not use one that arrived warm [1]. Date the vial the first time you puncture it [2]. Use a new sterile needle every time, and discard the vial 28 days after that first use [1], or at the beyond-use date on its label if that comes sooner. Discard it sooner if it turns cloudy or shows particles [4].

For the bigger picture, our semaglutide course covers how the drug works and what its trials found, and the retatrutide storage guide applies the same questions to a GLP-1 drug that has no label at all.