How to Store Peptides: Before and After Reconstitution

Creator: Peptide Me Editorial Team
Published: 2026-10-08

Most peptide storage advice online sounds precise: fridge, freezer, 30 days, 90 days. Very little of it has a source. The only storage numbers that come from real stability testing are on the labels of approved drugs, and those labels disagree with each other more than the advice does.

PMWritten byPeptide Me Editorial Team9 min read · Updated Oct 2026 · Reviewed against 11 sources

TL;DR

There is no single rule for peptides. FDA labels for approved peptides range from room-temperature powder (EGRIFTA) to refrigerate-until-first-use pens (OZEMPIC, MOUNJARO).
Almost every approved label says 'do not freeze'. For solutions, freezing is the one instruction the labels share.
Mixing starts a clock the label sets: immediately (EGRIFTA SV), 7 days at room temperature (EGRIFTA WR), 28 days in the fridge (GENOTROPIN with preservative), 24 hours (GENOTROPIN without preservative).
Light protection comes up again and again: 'keep in the original carton' appears on almost all of them.
For research peptides, published stability data is essentially absent. Fridge-life claims for those vials are borrowed, not measured.

The honest short answer is that a peptide should be stored exactly as its label says, and most research peptides have no label worth the name. For approved peptide drugs, FDA labels give tested instructions. Unopened injectable solutions such as OZEMPIC and MOUNJARO go in the refrigerator at 2–8°C (36–46°F) and must not be frozen^1,2. Some freeze-dried (lyophilized) products, such as EGRIFTA, are kept at room temperature before mixing^3,4. After a product is mixed or first used, the label sets a time limit, and that limit depends on the formulation. Labels on the market range from 'use immediately' to 56 days^1,3. For peptides sold without FDA review, no comparable data exists, so any storage rule for them is a borrowed rule. This guide goes through what the labels say, why those instructions exist, and what that means for a vial without one. Basic fridge handling after mixing is also in our guide on how to inject peptides.

Why peptides need careful storage at all

Peptides and proteins break down in two broad ways. Chemical instability changes the molecule itself. Physical instability changes how molecules fold or clump together. Formulation scientists deal with both in solution and in the dried state⁸. A review of peptide therapeutics lists what drives aggregation, the clumping that can make a peptide inactive or more likely to trigger an immune reaction. The list includes temperature, pH, concentration, surfaces and interfaces such as the air–water boundary, agitation, chemical changes such as deamidation and oxidation, and freeze-drying itself⁷. The same review notes that lyophilization is widely used, but can cause structural changes that show up as aggregation after the powder is mixed⁷.

Regulators are concerned with the same issues. When FDA placed a set of peptides nominated for compounding in its 'category 2' of substances that may present significant safety risks, it named the risk of immunogenicity 'due to the potential for aggregation or peptide-related impurities' again and again⁹. Storage can't fix a product that was poorly made. Poor storage can damage a product that was made well.

What approved peptide labels actually say

These are the only storage numbers in this field backed by stability testing that a regulator reviewed. They come from the current FDA labels on DailyMed:

Product	Form	Before first use / mixing	After first use / mixing	Freezing and light
OZEMPIC (semaglutide) pen	Solution, multi-dose pen	Refrigerator 2–8°C until the expiry date¹	56 days at 15–30°C or in the fridge¹	Do not freeze; do not use if frozen; protect from excessive heat and sunlight; keep cap on¹
MOUNJARO (tirzepatide) single-dose pen or vial	Solution, single-dose	Refrigerator 2–8°C; if needed, unrefrigerated up to 30°C for a total of 21 days²	Single-dose device²	Do not freeze; protect from heat and light; keep in carton²
MOUNJARO multi-dose vial or KwikPen	Solution with preservatives, 4 doses	Refrigerator until expiry; 30 days if kept at room temperature²	Fridge or up to 30°C; discard after 30 days at room temperature, 30 days after first use or 4 weekly doses, even if medicine is left²	Do not freeze; keep in carton²
EGRIFTA SV (tesamorelin)	Lyophilized powder + sterile water	Room temperature 20–25°C (excursions 15–30°C), in the box³	Inject immediately; if not used immediately, discard; do not freeze or refrigerate the mixed solution³	Protect from light in the original box³
EGRIFTA WR (tesamorelin)	Lyophilized powder + bacteriostatic water	Room temperature 20–25°C, in the box⁴	Room temperature 20–25°C; discard 7 days after mixing⁴	Do not freeze; protect from light⁴
VYLEESI (bremelanotide)	Solution, single-dose autoinjector	At or below 25°C (77°F)⁵	Single-dose, disposable autoinjector⁵	Do not freeze; protect from light⁵
GENOTROPIN 5 mg / 12 mg (somatropin, with preservative)	Lyophilized powder, two-chamber cartridge	Refrigerator 2–8°C until expiry⁶	Refrigerator between uses, up to 28 days; do not shake⁶	Do not freeze; protect from light⁶
GENOTROPIN MINIQUICK (somatropin, no preservative)	Lyophilized powder, single-dose device	Refrigerator; if needed up to 3 months at or below 25°C⁶	Up to 24 hours refrigerated; use once⁶	Do not freeze; protect from light⁶

Three patterns stand out. First, the form of the product doesn't predict the rule. Two lyophilized products (EGRIFTA and GENOTROPIN) have opposite instructions before mixing: room temperature for one, refrigerator for the other^3,6. Second, the preservative sets the in-use window more than the molecule does. The same somatropin gets 28 days in a preserved cartridge and 24 hours without a preservative⁶, and multi-dose MOUNJARO contains benzyl alcohol and phenol that the single-dose versions don't². Third, no label tells you to put anything in a freezer.

Track your TRT protocol in Peptide Me

Log every shot, rotate injection sites, and chart your bloodwork over time.

Download on theApp Store

Before reconstitution: the lyophilized powder

Freeze-drying removes water, and keeping proteins stable in the dried state rather than in solution is a standard formulation approach⁸. It does not make the powder indestructible. The labels still set a temperature range and require light protection, and EGRIFTA's range is ordinary room temperature, not a fridge^3,4. The GENOTROPIN MINIQUICK label shows that 'refrigerate' and 'room temperature for a while' can both be correct for one product. The limit is set by testing: up to 3 months at or below 25°C⁶.

The advice to freeze research powder for long-term storage is common. We could not find published stability data behind it for any research peptide product. None of the approved lyophilized peptide labels above uses a freezer^3,4,6. That doesn't prove freezing dry powder is harmful. It means the recommendation has no data we can cite either way.

What the labels agree on for powders:

Keep the vial in its original box or carton, because the labels ask for protection from light^3,4,6.
Stay inside the stated temperature range. Brief excursions are allowed only when the label names them (EGRIFTA: 15–30°C)³.
Keep the diluent with the drug and store it as its own label says. The EGRIFTA injection box with its water is kept at room temperature^3,4, and bacteriostatic water vials are labeled for 20–25°C¹⁰.

After reconstitution: the clock starts

Once a powder is in solution, it is exposed to every pathway that water enables, and the label limits drop sharply. EGRIFTA SV, mixed with sterile water, allows no storage at all. It is injected right away, and the label rules out refrigerating or freezing the solution³. EGRIFTA WR, mixed with bacteriostatic water, lasts 7 days, but at room temperature rather than in the fridge⁴. GENOTROPIN with preservative goes in the fridge between uses for up to 28 days⁶. The idea that the fridge is always safer after mixing fails on the EGRIFTA SV label.

The choice of diluent matters too. Our guide to bacteriostatic water explains why a preservative-free water is meant for a single entry, and why the 28-day figure is a rule for the container, not a stability result for what's dissolved in it.

◑ Limited human dataResearch peptides (BPC-157, TB-500, CJC-1295, ipamorelin and similar) have no FDA-reviewed stability data. We found no published studies measuring how long any such product keeps its potency after reconstitution in real-world storage. Fridge lives of '30 days' or '4–6 weeks' on these products come from approved-drug labels or the CDC multi-dose rule, not from testing of the product in your hand.

Fridge, freezer, heat and light

The refrigerator

When a label says refrigerate, it means 2–8°C (36–46°F)^1,2,6. The OZEMPIC label adds a detail many people miss: do not store it 'directly adjacent to the refrigerator cooling element'¹. The back of a fridge shelf can freeze a vial without the fridge ever reaching 0°C.

The freezer

Every approved solution label above says not to freeze it, and OZEMPIC and MOUNJARO also say not to use the product if it has been frozen^1,2. A vial that froze by accident is not the same product any more, even if it looks clear after thawing.

Heat and time out of the fridge

Where labels allow time at room temperature, they give a number and a ceiling. For MOUNJARO single-dose pens that is up to 30°C for 21 days in total, and for OZEMPIC pens after first use it is 15–30°C for 56 days^1,2. These are tested allowances for those formulations. They are not a general rule that peptides survive a few weeks warm.

Light

'Keep in the original carton' and 'protect from light' appear on nearly every label here^1,2,3,4,5,6. For an unlabeled vial, the cheapest precaution is to keep it in its box or another opaque container.

Signs a vial should not be used

Approved labels tell users to look before injecting. EGRIFTA says to use the mixed solution only if it is 'clear, colorless and without particulate matter'^3,4. Cloudiness, flakes, color change or a ring of residue are reasons to discard. A clear solution, though, doesn't prove the peptide is still intact. Aggregation and chemical degradation can happen before anything is visible⁷. Other reasons to throw a vial out, based on the labels: it has been frozen^1,2, it is past its in-use window^2,4,6, or it has been outside its temperature range for longer than the label allows².

A practical approach when there is no label

Without product-specific data, the approved labels are the most conservative guide available. They are not a guarantee. Reasonable habits that follow from them:

Keep solutions at 2–8°C, away from the cooling element, in a box that blocks light¹.
Never freeze a reconstituted vial^1,2,4,6.
Swirl gently to dissolve; don't shake. Several labels say so, and agitation speeds up aggregation^4,6,7.
Mix only as much as you will use in a short period. Treat any stated fridge life as an upper limit, not a promise.
Write the mixing date on the vial. The CDC's multi-dose rule starts at first puncture¹¹, and every in-use window above starts at mixing or first use.

None of this makes an untested product safe or potent. It only avoids adding storage damage on top of unknown quality. The broader question of what research peptides can and can't promise is covered in are peptides safe?. If you track vials in Peptide Me, logging the mix date with the vial lets the app show how long each open vial has been in use.

This is storage information, not medical advice

The numbers above are quoted from the current FDA labels of the named products and apply to those products only. If you use a prescribed peptide, follow its label and ask your pharmacist about anything that isn't covered, such as travel or a power cut. Nothing here recommends using any peptide.

⚠︎Educational information only — not medical advice. Injection technique carries real risks; get hands-on guidance from a licensed clinician before self-administering anything.

FAQ

For approved peptide solutions, the fridge at 2–8°C, and never the freezer: every label reviewed here says not to freeze, and some say not to use a product that has frozen. Some lyophilized products, such as EGRIFTA, are stored at room temperature before mixing. No approved label reviewed here uses a freezer.

It depends on the product, and only approved products have tested answers. Labels range from use immediately (EGRIFTA SV), to 7 days at room temperature (EGRIFTA WR), to 28 days refrigerated (GENOTROPIN with preservative). For research peptides there is no published stability data, so any figure is borrowed.

Some approved ones can: EGRIFTA SV and WR powders are labeled for 20–25°C, and GENOTROPIN MINIQUICK can spend up to 3 months at or below 25°C. Others, like the GENOTROPIN 5 mg and 12 mg cartridges, are labeled for the fridge. The product's own testing decides, not the fact that it is a powder.

For solutions, the approved labels treat it as unusable. OZEMPIC and MOUNJARO both say not to use the product if it has been frozen. Freezing can damage a peptide in ways you can't see, so a clear-looking vial after thawing is not proof it is intact.

Almost every approved peptide label reviewed here says to keep the product in its original carton or protect it from light. For an unlabeled vial, keeping it in its box or an opaque container is the simplest precaution.

Not that we could find. Research peptides have no FDA-reviewed stability testing, and we found no published studies of how long such products keep their potency after mixing. Storage advice for them borrows from approved-drug labels or general infection-control rules.

References

Primary sources — PubMed / NEJM / The Lancet.

DailyMed (U.S. National Library of Medicine). OZEMPIC (semaglutide) injection — Prescribing Information, Novo Nordisk. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=adec4fd2-6858-4c99-91d4-531f5f2a2d79
DailyMed (U.S. National Library of Medicine). MOUNJARO (tirzepatide) injection — Prescribing Information, Eli Lilly and Company. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=d2d7da5d-ad07-4228-955f-cf7e355c8cc0
DailyMed (U.S. National Library of Medicine). EGRIFTA SV (tesamorelin) for injection — Prescribing Information, Theratechnologies Inc. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=3d783378-b02d-4f19-99dd-0fc91a042224
DailyMed (U.S. National Library of Medicine). EGRIFTA WR (tesamorelin) for injection — Prescribing Information, Theratechnologies Inc. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=839334d3-8c1d-4c26-9036-2ab524a6ea75
DailyMed (U.S. National Library of Medicine). VYLEESI (bremelanotide) injection — Prescribing Information, Cosette Pharmaceuticals. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=f1d0c1b5-2f39-4bad-a6a4-0066e3ad5dcf
DailyMed (U.S. National Library of Medicine). GENOTROPIN (somatropin) for injection — Prescribing Information, Pfizer. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=ffebf88b-d257-4542-9808-74d9b7167765
Zapadka KL, Becher FJ, Gomes dos Santos AL, Jackson SE. Factors affecting the physical stability (aggregation) of peptide therapeutics. Interface Focus. 2017;7(6):20170030. https://pmc.ncbi.nlm.nih.gov/articles/PMC5665799/
Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharm Res. 2010;27(4):544-575. https://pubmed.ncbi.nlm.nih.gov/20143256/
U.S. FDA. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks (content current as of 04/22/2026). https://www.fda.gov/drugs/human-drug-compounding/certain-bulk-drug-substances-use-compounding-may-present-significant-safety-risks
DailyMed (U.S. National Library of Medicine). Bacteriostatic Water for Injection, USP — label, Hospira, Inc. Revised 08/2019. https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=87d6e9dc-fe3b-4593-ac9a-d7493d1959c7
Centers for Disease Control and Prevention. Preventing Unsafe Injection Practices. Injection Safety. https://www.cdc.gov/injection-safety/hcp/clinical-safety/index.html