How Long Do Peptides and Compounded GLP-1s Last? Fridge, Room Temperature and Travel

The short answer depends on what is in your hand. A brand-name GLP-1 pen has a tested number printed on its FDA label: a single-dose Zepbound pen or vial may sit unrefrigerated for up to 21 days¹, and a single-dose Wegovy pen for up to 28 days before its cap comes off². A compounded semaglutide or tirzepatide vial should be thrown away 28 days after the first needle goes in, and FDA says to do that even if the pharmacy's instructions say it lasts longer⁴. A research peptide you mixed yourself has no tested number at all.

That last point is the one most storage guides get wrong. The "28 days" people repeat about bacteriostatic water is not printed on the bacteriostatic water label. The Hospira label we read gives a storage temperature for the unopened vial and then says the opposite of what most guides imply: "Do not store reconstituted solutions of drugs for injection unless otherwise directed by the manufacturer of the solute"⁵. A research peptide has no manufacturer directions to follow. The 28-day figure is a general rule for opened multi-dose containers, and it is about germs, not about whether the peptide inside is still intact.

If a shipment has already arrived warm, start with what to check before using delivered GLP-1 medication. A storage limit on a branded pen does not establish stability for a compounded vial.

What a beyond-use date is

Every compounded vial should carry a beyond-use date, or BUD. The United States Pharmacopeia, whose chapter on sterile compounding (USP 797) became official on November 1, 2023, defines it as "the date, or the hour and date, after which the CSP must not be used"³. CSP means compounded sterile preparation, which is what a compounded GLP-1 vial is.

Three rules in that chapter matter to a patient:

• •Colder storage earns a longer date. USP's own explanation is that cold slows both microbial growth and chemical breakdown. Its rule of thumb is that reaction rates roughly double for every 10°C rise, so a product kept at room temperature gets about a quarter of the time it would get in the fridge³.
• •Dates do not stack. A vial dated for room-temperature storage cannot be put back in the fridge to win extra time³.
• •Multi-dose containers carry a 28-day ceiling after first entry unless their labeling says otherwise, and an aqueous multi-dose compounded product must pass antimicrobial effectiveness testing³.

The CDC states the same 28-day rule for opened multi-dose vials in clinics: date it and discard it within 28 days "unless the manufacturer states another date for that opened vial"⁶. For compounded GLP-1s, FDA goes one step further. It tells patients to discard the vial 28 days after first use "even if medication remains in the vial", and not to keep using it "even if instructions from the compounder say the medication can be used for longer than 28 days"⁴.

That matters for how vials are sized. Invyncible lists its compounded semaglutide starter as a 2.5 mg vial meant to last about five weeks. On a weekly schedule, the fifth dose falls after day 28, so ask the dispensing pharmacy what date its own label prints before you plan the last dose.

Brand labels: Zepbound and Wegovy

The brand labels are the only places in this market where storage times have actually been tested and approved. The numbers differ by device, so read the one that matches yours.

Zepbound (tirzepatide) has two families¹:

• •Single-dose pen or single-dose vial: refrigerate at 36°F to 46°F (2°C to 8°C). If needed, each one can be kept unrefrigerated at up to 86°F (30°C) for up to 21 days. Once it has been at room temperature, do not put it back in the fridge, and discard it if it is not used within 21 days of leaving the fridge.
• •Multi-dose vial or KwikPen: unopened and refrigerated, it lasts until the printed expiration date; unopened at room temperature, 30 days. Once opened, it can live in the fridge or at room temperature, and must be thrown away after 30 days at room temperature, 30 days after first use, or after four weekly doses, whichever comes first, even if medicine is left.

Wegovy (semaglutide) has three²:

• •Single-dose pen or syringe: refrigerate. If needed, before the cap comes off, it can be kept between 46°F and 86°F (8°C to 30°C) for up to 28 days.
• •Wegovy FlexTouch (multi-use pen): refrigerate before first use. After first use it lasts 56 days, either in the fridge or between 59°F and 86°F (15°C to 30°C).
• •Wegovy tablets: no fridge at all. Store at 68°F to 77°F (20°C to 25°C) in the original bottle, away from moisture.

Both labels agree on the two things that ruin a pen fastest: freezing and light. Never freeze either drug, never use one that has frozen, and keep it in its carton. Wegovy's label adds that it should not sit right next to the fridge's cooling element².

If you are choosing between these products rather than storing one, our tirzepatide provider rankings and semaglutide provider rankings compare brand and compounded options side by side.

Compounded GLP-1 vials

A compounded vial does not come with an FDA-reviewed label. The agency does not review compounded drugs "for safety, effectiveness or quality before they are marketed"⁴. The storage time is whatever the pharmacy assigned under USP rules, capped for patients at 28 days after first use by FDA's guidance. Keep it refrigerated, since FDA notes injectable GLP-1s "require refrigeration as indicated in their package inserts"⁴.

Light deserves more respect with these vials than most people give it. In a study by Novo Nordisk scientists, so read it knowing the brand's maker ran it, compounded semaglutide samples exposed to light showed significant differences in strength, total impurities and high-molecular-weight protein compared with the original product¹⁰. Keep the vial in its box, in the fridge, between doses.

Bacteriostatic water and the 28-day rule

Bacteriostatic water is sterile water with 0.9% or 1.1% benzyl alcohol, sold in multiple-dose containers "from which repeated withdrawals may be made"⁵. The unopened vial is stored at 68°F to 77°F (20°C to 25°C). The preservative is why a vial can be punctured more than once. It is also why the label carries a hard warning: benzyl alcohol must not be used in newborns⁵, after it was linked to a fatal "gasping syndrome" in premature infants¹¹.

The 28-day number belongs to the container, not to whatever you dissolved in it. Our bacteriostatic water guide covers the water itself, and the bac water calculator works out how much to add.

Unmixed powder and mixed research peptides

Research peptides ship as freeze-dried powder because peptides and proteins are generally far more stable as a dry solid than in water⁷. Once dissolved, they start to break down through reactions such as deamidation, oxidation and aggregation, at rates set by temperature, pH and time⁸.

Here is the honest limit. No FDA label exists for BPC-157, TB-500 or any other research peptide, so no tested shelf life exists either, powder or mixed. A vendor's "lasts 30 days once mixed" is a claim, not a stability study. The safest working rule is the one the chemistry supports: keep the powder cold and dry, mix only what you will use soon, refrigerate the mixed vial, and do not stretch it. Our reconstitution guide walks through the mixing itself.

Signs a vial or pen has gone off

The labels describe what good medicine looks like. Wegovy should be clear and colorless². Zepbound should be clear and colorless to slightly yellow, and its instructions say not to use it if it has been frozen, has particles, is cloudy, or is discolored¹.

A dose that looks normal can still be weak. A review of insulin storage, another peptide hormone, found that household refrigerators often miss the recommended range⁹. A cheap fridge thermometer is worth more than any guess.

Travel and shipping

Flying. TSA allows larger amounts of medically necessary liquids "in reasonable quantities for your flight." Ice packs and gel packs may come through "in a frozen, partially frozen or melted state," and you can ask that liquid medication not be X-rayed or opened¹². The CDC advises keeping medicine in your carry-on and in its original labeled container, and checking the rules of the countries you will visit, since some require a prescription or a doctor's letter¹³.

How long it can be out. A brand pen gives you slack. A Zepbound single-dose pen can go up to 21 days at or below 86°F, and an unopened Wegovy single-dose pen up to 28¹². A compounded vial has no tested room-temperature window, so keep it cold the whole trip.

Delivery. FDA has received complaints that some compounded GLP-1s "arrived warm or with inadequate ice packs"⁴. What sellers promise varies:

• •Trimi includes overnight cold-chain shipping at every plan tier and names its compounding pharmacy.
• •Invyncible offers four shipping speeds, but every refrigerated program can only ship overnight cold — none of the slower options.
• •Boston Medical Group ships monthly with ice packs, along with syringes and alcohol swabs.
• •TRYM Health describes its shipping as free and temperature-controlled in insulated packaging.
• •Even on the brand side, Cost Plus Drugs ships its generic liraglutide pens next-day refrigerated.

If a box arrives warm, with melted packs and a vial that is warm to the touch, photograph it and call the pharmacy before you inject anything.

The bottom line

Brand pens have tested windows: 21 days unrefrigerated for single-dose Zepbound, 28 days for an unopened single-dose Wegovy pen, 56 days for an opened Wegovy FlexTouch. Compounded vials get one number from FDA: 28 days after first use, then discard. Mixed research peptides get no tested number at all, and the bacteriostatic water label does not supply one. When the label is silent, cold, dark and short is the only rule the evidence backs.