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We found no stability study of unapproved peptides dissolved at home; the firmest rule we found is FDA's general advice to use a multiple-dose vial of a sterile medication within 28 days of first use and then discard it, even if some is left, because the risk of contamination rises after 28 days.[1]
The short answer
| What you have | What the source says | Source |
|---|---|---|
| A multiple-dose vial of a sterile medication | Generally, use within 28 days after first use, then discard it even if medication remains; a product's own label can set a different limit | FDA [1] |
| A drug you dissolved in bacteriostatic water | The water's label: do not store reconstituted solutions unless the drug's manufacturer directs it | DailyMed label |
| Bacteriostatic water | A multiple-dose vial with a benzyl alcohol preservative, stored at 20 to 25°C | DailyMed label |
| Wegovy pen, before first use | Refrigerate at 2 to 8°C; if needed, up to 28 days at 8 to 30°C before the cap comes off; do not freeze; protect from light | [2] |
| Zepbound multi-dose vial or KwikPen, once in use | Throw it away after a total of 30 days at room temperature, 30 days after first use, or 4 weekly doses, even if medicine is left | [3] |
| A compounded GLP-1 drug that arrives warm | Do not use it | FDA [1] |
| An unapproved peptide powder, once dissolved | We found no stability study | See the last section; FDA's search found no approved product containing BPC-157 in any country [4] |
Where the 28-day number comes from
FDA's general advice covers vials that hold multiple doses of a sterile medication: use them within 28 days after first use, discard them after that even if medication remains, and do not keep using one even if a compounder's instructions say it lasts longer [1]. FDA gives contamination as the reason [1]. We found no statement in that FDA advice about whether the medication itself stays potent for 28 days.
The 28-day discard date in the SoftMaxx AI vial planner matches this FDA advice [1].
A product's own label can set a different limit for that product [3][2]. The Zepbound multi-dose vial's label limit is 30 days after first use or 4 weekly doses [3], and the Wegovy label allows its multi-use FlexTouch pen 56 days after first use [2].
- Regulator document FDA recommends discarding a multiple-dose vial of a sterile medication 28 days after first use, even if medication remains, because the risk of contamination rises after 28 days. It also advises a new, sterile needle and syringe for every dose, because reusing them can contaminate the medication.[1]
What the bacteriostatic water label says
The bacteriostatic water label we read on DailyMed describes sterile, nonpyrogenic water with 0.9% or 1.1% benzyl alcohol added as a preservative, in a multiple-dose container from which repeated withdrawals may be made. The label lists storage at 20 to 25°C (DailyMed label). Its warning reads "NOT FOR USE IN NEONATES", because benzyl alcohol has been associated with toxicity in newborns.
The same label says to use aseptic technique for every entry into the vial, to use a dissolved drug promptly, and not to store reconstituted solutions of drugs unless the drug's manufacturer directs it (DailyMed label). It warns that some drugs may be incompatible with a vehicle that contains benzyl alcohol. It gives no in-use day limit for the water vial itself.
Signs a solution should not be used, from the labels
- Bacteriostatic water: inspect a dissolved drug for clarity and for unexpected precipitation or discoloration, and do not use the water unless the solution is clear and the seal intact (DailyMed label).
- Wegovy: use only if the solution is clear, colorless and contains no particles; do not use it if it has been frozen; throw the pen away if it has been exposed to light or to temperatures above 30°C [2].
- Zepbound: it should look clear and colorless to slightly yellow; do not use it if you see particles or discoloration, or if it has been frozen [3].
- Compounded GLP-1 drugs: FDA recommends not using one that arrives warm or with too little refrigeration, because this can affect its quality [1].
We found no label or regulator text that gives visual discard signs for unapproved peptides.
Unapproved peptides: what we could not find
We searched PubMed on 2026-09-30 and found no published study of how long BPC-157, TB-500 or GHK-Cu stays stable after being dissolved at home. FDA's briefing reports that its search found no approved product containing BPC-157 in any country [4], so there is no manufacturer storage instruction of the kind the Wegovy and Zepbound labels carry.
- Regulator document FDA's July 2026 briefing on BPC-157 reports storage figures for the powder and for solutions, but the sources it cites for those figures are commercial product pages, not stability studies. FDA adds that peptides like BPC-157 can be extremely sensitive to formulation, pH, heat and concentration, which may lead to aggregation, degradation and a loss of biological activity.[4]
- Regulator document The same briefing says significant amounts of aggregates can form in formulated products, especially during storage or under stress, and lists storage conditions that favor impurities and peptide aggregates, which can provoke immune responses, among the factors that can harm the safety of compounded BPC-157.[4]
- Expert review A 2026 review says no pharmaceutical-grade formulation of BPC-157 has been developed or validated, and that it lacks formal excipient compatibility studies.[5]
- Regulator document Health Canada warns that unauthorized peptide drugs may be improperly manufactured or stored.[6]
Report a side effect
If something went wrong after using any product, tell a clinician and report it. Reports are how regulators find contaminated or mislabeled products.
- FDA MedWatch (United States)
- Canada Vigilance Program (Canada)
Common questions
How long does a reconstituted peptide last in the fridge?
We found no stability study for unapproved peptides dissolved at home. FDA's general advice for multiple-dose vials of sterile medications is to discard them 28 days after first use, for contamination reasons, and the bacteriostatic water label says not to store reconstituted solutions unless the drug's manufacturer directs it.[1] Source: DailyMed document
Does the 28-day rule mean a peptide stays potent for 28 days?
Regulator document No source we found says so. FDA gives contamination as the reason for the 28-day limit and says nothing about potency.[1]
Can you freeze reconstituted peptides?
We found no study of freezing unapproved peptide vials mixed at home. The Wegovy and Zepbound labels say not to freeze those medicines and not to use them if they have been frozen.[2][3]
How long is bacteriostatic water good for after opening?
The label we read gives no in-use day limit; it describes a multiple-dose vial stored at 20 to 25°C. FDA's general advice for multiple-dose vials of sterile medications is to use them within 28 days after first use.[1] Source: DailyMed document
How should Wegovy be stored?
Drug label In the refrigerator at 2 to 8°C. If needed, before the cap comes off, the pen can be kept at 8 to 30°C for up to 28 days. Do not freeze it, keep it in its carton away from light, and throw it away if it has been frozen or exposed to temperatures above 30°C.[2]
What if my GLP-1 medicine arrived warm?
Regulator document FDA recommends not using any injectable GLP-1 drug that arrives warm or with insufficient refrigeration, because this can affect the drug's quality.[1]
References
Every reference below was matched to its PubMed or DOI record (title checked) before publication. "Verified" means the paper exists and is the one named; what it supports is stated next to each claim.
FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss
SourceWEGOVY (semaglutide) injection; WEGOVY (semaglutide) tablets — Prescribing Information
SourceZEPBOUND (tirzepatide) injection — Prescribing Information
SourceJuly 23-24, 2026, Meeting of the Pharmacy Compounding Advisory Committee – FDA Briefing Document for BPC-157-Related Bulk Drug Substances (BPC-157 (free base) and BPC-157 acetate)
SourceBPC-157 as an Investigational Peptide Therapeutic: Biopharmaceutical Challenges, Formulation Strategies, and Translational Development Barriers.
PubMed 42198317 DOIThink twice before injecting peptides bought online: unauthorized products can seriously harm you (Health Canada advisory; lists KPV)
Source
Keep reading
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