Peptide storage temperature: what the label actually says.
Lyophilised powder and reconstituted solution are different storage problems with different temperature answers, and the powder answer is not even the same across compounds. Three FDA-approved lyophilised peptide labels, read side by side, show why a single storage number does not exist.
"What temperature should a peptide be stored at" gets asked as though it has one answer. It has at least two, because a sealed vial of freeze-dried powder and an opened vial of solution are not the same storage problem, and — less intuitively — even the powder answer is not fixed. Three FDA-approved lyophilised peptide products, compared directly below from their own current labelling, specify three different storage regimes for the unreconstituted powder: two at room temperature, one refrigerated.
This post is written for researchers and laboratory personnel storing research compounds, not for anyone administering anything. It compares real, currently marketed lyophilised peptide and protein products by what their FDA labelling actually states, to make one point concrete: a storage-temperature instruction belongs to a specific compound and its specific formulation, and general rules only go as far as identifying the right question to check against the supplier's own documentation.
Key takeaways
- Lyophilised powder and reconstituted solution are separate storage problems: dry peptide is kinetically stable enough to tolerate a range of temperatures, dissolved peptide is not.
- The powder-storage temperature is not universal even among approved products: FDA labelling for EGRIFTA SV (tesamorelin) and Glucagon for Injection both specify room temperature, 20–25°C, while Genotropin (somatropin) specifies refrigeration at 2–8°C — three formulations, three different answers.
- Once reconstituted, the regimes diverge further still: EGRIFTA SV's label states the mixed solution must not be stored, frozen or refrigerated at all; Genotropin's states refrigerated storage for up to 28 days; Glucagon's states immediate use with no storage window at all.
- A supplier's own documentation for a specific compound and lot overrides any general convention, because it reflects that formulation's actual stability data.
- Protection from light and avoidance of repeated freeze-thaw cycling apply regardless of which temperature a given compound's label specifies.
Two storage problems, not one
A lyophilised peptide is a dry, amorphous solid in which the molecule is kinetically trapped: with water removed, the hydrolysis, oxidation and aggregation routes that break a peptide down in solution are largely unavailable. That is the entire purpose of freeze-drying, and it is why the dry form tolerates conditions the dissolved form cannot.
Reconstitution reverses that in one step. The moment water enters the vial, every water-dependent degradation pathway becomes available again, and the storage question changes from months or years to days or weeks. The stability guide linked below covers the chemistry of each pathway in full; this post stays with the narrower, more practical question — what temperature applies to which state.
What the label actually says: three approved products, compared
Research literature on peptide storage is thin, and vendor pages tend to state one number without a source. Regulatory product labelling is the opposite: dense, product-specific, and legally required to state the storage conditions the formulation was actually tested under. Reading three current FDA labels for lyophilised peptide and protein products side by side is enough to make the point that a single storage number does not generalise.
| Product (active peptide) | Lyophilised powder, before reconstitution | After reconstitution |
|---|---|---|
| EGRIFTA SV (tesamorelin) | Room temperature, 20–25°C; excursions to 15–30°C permitted [USP Controlled Room Temperature] | Label states: do not store, freeze or refrigerate after mixing — single-dose vial, discard unused portion |
| Genotropin (somatropin) | Refrigerated, 2–8°C, kept in the original package to protect from light | Refrigerated, 2–8°C, for up to 28 days, protected from light |
| Glucagon for Injection | Room temperature, 20–25°C; label separately instructs: do not freeze | Label states: use immediately, discard unused portion — no multi-day storage window is given |
EGRIFTA SV (tesamorelin)
The current label reads: "Store EGRIFTA SV 2 mg vial at room temperature at 20°C to 25°C (68°F to 77°F); excursions permitted to 15°C to 30°C (59°F to 86°F) [See USP Controlled Room Temperature]." After mixing, it reads: "Do not store, freeze or refrigerate EGRIFTA SV after it has been mixed with the Sterile Water." AKH's own tesamorelin listing carries the same active peptide.
Genotropin (somatropin)
The current label's storage section reads: "Store GENOTROPIN lyophilized powder under refrigeration at 36°F to 46°F (2°C to 8°C) until the expiration date," and, after reconstitution, "Store under refrigeration at 36°F to 46°F (2°C to 8°C) between each use, for up to 28 days." That is the opposite convention from EGRIFTA SV's room-temperature powder — the same class of freeze-dried peptide/protein product, formulated differently, labelled differently.
Glucagon for Injection
The current label's storage section reads: "Before Reconstitution: Store Glucagon for Injection at 68°F to 77°F (20°C to 25°C)… Do not freeze. Keep in its original package and away from light. After Reconstitution: Use reconstituted Glucagon for Injection immediately. Discard unused portion." No multi-day reconstituted storage window is stated at all — a third distinct pattern.
Before reconstitution, in practice
None of the three regimes above is "the" lyophilised peptide storage temperature — each is that specific formulation's tested condition. Suppliers of research peptides converge on their own conventions the same way: AKH's own product documentation specifies frozen storage, at approximately -20°C, for lyophilised stock until reconstitution, which is a more conservative default than either room-temperature label above and consistent with the refrigerated convention Genotropin's label uses.
That frozen convention coexists with the fact lyophilised material tolerates ambient temperatures for the length of ordinary transit — the two statements describe different timescales, not a contradiction. A dry powder that survives days at ambient temperature in a parcel is not thereby a candidate for indefinite room-temperature storage on a shelf; freezing is the more conservative choice for the storage duration a supplier is actually committing to, and it is why -20°C, not room temperature, is the default most research-peptide documentation states.
After reconstitution, the target narrows
Once water enters the vial, the range of acceptable answers narrows sharply regardless of which powder-storage regime applied beforehand. The reconstituted-peptide post linked below covers the degradation timeline in detail; the storage-temperature answer for that state, across AKH's own documentation and the stability guide alike, is refrigeration at 2–8°C, protected from light, without repeated freeze-thaw cycling and without refreezing once thawed.
The three labels above show why that narrower target still is not one universal number: a reconstituted vial can be a 28-day refrigerated preparation, a same-day-only preparation with no refrigeration permitted at all, or a use-immediately preparation with no storage window whatsoever, depending entirely on the formulation. Refrigeration is the safer default once any peptide is in solution; the specific number of days it stays usable there is compound-specific and belongs on that compound's own documentation, not on a general page.
Reading a storage instruction in practice
Reduced to a short procedure, four checks cover the cases that actually occur; anything more specific should be resolved against the supplier's documentation for the exact compound and lot rather than against a general rule.
- 01
Identify the state first
Lyophilised powder and reconstituted solution are different storage problems with different acceptable temperature ranges — confirm which one a given instruction addresses before applying it.
- 02
Do not extrapolate one compound's regime to another
Room temperature for one lyophilised product and refrigeration for another are both correct — for their own formulations. The label comparison above is real evidence that this varies, not an argument for picking whichever regime is more convenient.
- 03
Treat the supplier's documentation as the final word
General conventions — a frozen default for powder, a refrigerated default for solution — are reasonable starting points, not substitutes for a specific product's own storage instructions.
- 04
Protect against light and freeze-thaw cycling regardless of temperature
Every label compared above keeps material in its original package away from light, and none endorses repeated freezing and thawing. Those two practices apply across formulations even where the temperature target itself does not.
Common questions.
- What is the right peptide storage temperature?
There is no single number. Lyophilised powder and reconstituted solution require different storage conditions, and even among lyophilised products the powder-storage temperature varies by formulation — current FDA labelling specifies room temperature (20–25°C) for some lyophilised peptide products and refrigeration (2–8°C) for others. The correct answer is compound-specific and stated in that product's own documentation.
- How should lyophilised peptide be stored before reconstitution?
It depends on the formulation. Some approved lyophilised peptide products are labelled for room-temperature storage (20–25°C), others for refrigerated storage (2–8°C) — the FDA labelling for EGRIFTA SV (tesamorelin) and Genotropin (somatropin) specify opposite regimes for that reason. Research-peptide suppliers, including AKH, commonly default to frozen storage at approximately -20°C for lyophilised stock as a conservative convention, which is consistent with the more cautious of those two label conventions.
- Does lyophilised peptide need to be refrigerated?
Not universally. Genotropin's current label specifies refrigeration for its lyophilised powder, while EGRIFTA SV's and Glucagon for Injection's labels both specify room-temperature storage for theirs — all three are lyophilised peptide or protein products with FDA-approved labelling, and they do not agree. Whether refrigeration is required depends on the specific formulation, not on the fact that the material is lyophilised.
- Can lyophilised peptide be stored at room temperature?
For some formulations, yes — current labelling for EGRIFTA SV (tesamorelin) and for Glucagon for Injection both specify room-temperature storage (20–25°C, with limited excursions) for the unreconstituted powder. That is a property of those specific formulations, not a general rule; other lyophilised peptide products are labelled for refrigerated storage instead, and research-peptide suppliers commonly default to frozen storage as the more conservative convention absent product-specific data.
- What temperature should a reconstituted peptide be kept at?
Refrigerated, 2–8°C, protected from light, is the consistent answer across AKH's own documentation and the stability guide once water has been added. How long a reconstituted solution remains usable at that temperature is a separate, compound-specific question — current labelling ranges from a 28-day refrigerated window to no storage window at all once mixed, depending on the formulation.