Concretely: minus 20 °C · oral semaglutide.
The claim is plausible, which is exactly why I want to check it.
I am able to read a paper if someone points me at one.
Can anyone point me at a primary source, or confirm that there is not one?
minus 20 °C is colder than anything a lyophilised cake needs. minus 20 °C is 25 kelvin below a refrigerator, and below the glass transition of a lyophilised cake the ten-degree rule of thumb stops applying at all — solid-state chemistry is not slow liquid chemistry, it is a different regime, and the failure modes that survive it are mechanical rather than chemical. A dry cake has no solvent to react in, so the marginal benefit below a domestic freezer is small and the marginal risk is not: freeze-thaw on the way in and out, and condensation on a cold stopper when you open it, are the failure modes that actually happen at minus 20 °C. Nothing here is medical advice, and research-use-only material is not approved for human use.
Start with the physical state, because lyophilised and reconstituted material have completely different storage answers.
Reconstituted with a preservative-containing diluent: refrigerated, conventionally treated as usable for about 28 days from first entry. Without a preservative, single use and discard.
Keep vials in their original carton or in an opaque box. Light exposure matters for tryptophan-containing sequences and for anything with a chromophore, and a closed box is free.
Residual moisture is the dominant determinant of solid-state stability, which is why desiccants accompany lyophilised material.
A printed expiry on research-grade material has no stability programme behind it.
Keep the desiccant with the vial and the certificate with the lot code.
edited 20 Apr 2026 by halvard_ness — corrected a unit error in the worked example
HPLC purity, identity confirmation and quantified content on the vial you actually hold. Reports arrive with the chromatogram attached, not just a number.
Submit a sampleFounded 1998. ISO 9001 and cGMP certified, 1,500+ staff and 200+ patents. The synthesis house behind a great many of the vials that get sent out for testing - batch-specific documentation with every order.
Visit GL BiochemAnswering this needs the intended duration, since a fortnight and two years call for different arrangements.
Position matters less than people think: upright or on its side makes no difference to a lyophilised powder, and upright is marginally better for a reconstituted vial because it keeps the stopper dry.
Lyophilised powder: refrigerated at two to eight degrees for months, frozen at minus twenty for longer. The gain from minus eighty over minus twenty is small for a dry solid and is not usually worth the arrangement.
Photodegradation of tryptophan-containing peptides is documented and is the basis for light-protected storage recommendations.
Appearance does not indicate stability; a normal-looking cake can be substantially degraded.
Dry, cold, dark, still. Four words and you have the answer.
Answer first: dry, cold, dark and still, with the lot code where you can still read it in a year.
Store with the desiccant sachet if one was supplied, inside the secondary container rather than loose in a drawer. Residual moisture is the dominant variable in solid-state stability.
Label the vial at reconstitution with the date, the concentration and the resulting units per dose. This is the single most useful thirty seconds in the whole process.
Two-to-eight-degree refrigeration and minus-twenty freezing are the standard storage conditions for lyophilised peptides in supplier documentation across the market.
Nothing here is medical advice, and research-use compounds are not approved for human use.
Label the vial at reconstitution with date, concentration and units per dose.
Put another way, this is the tag where the advice is cheapest to follow and most often ignored.
Keep the certificate with the vial, physically or as a photograph filed under the lot code. A vial without a traceable certificate is an anonymous vial regardless of where it came from.
The 28-day in-use period for preservative-containing multi-dose preparations is printed on the diluent labelling and is a long-standing pharmacy convention.
The caveat is that storage conditions preserve what you have and cannot improve it.
Minus eighty buys very little over minus twenty for a dry solid.
Keep the paperwork with the material, or the material becomes anonymous.
Let a refrigerated or frozen vial equilibrate to room temperature before opening, so humid air does not condense water onto a cold cake.
The caveat is that "within specification" and "unchanged" are different claims. A vial can lose a few per cent of content and still be usable for its purpose while no longer matching its certificate.
Equilibrate before opening or you condense water into the cake.
edited 19 May 2026 by Dr_Idris_Coulibaly — fixed an arithmetic slip in the third paragraph
Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.