How Long Does Retatrutide Last? Before and After Mixing
Lyophilised retatrutide, sold as reta (GLP-3), keeps longest sealed, dry, dark and cold; once mixed with bacteriostatic water it lasts 8 to 12 weeks at 2 to 8 °C under Vistara Labs’ handling guidance, with quality beginning to drop at around week 6. A mixed vial is not frozen, not left warm and not left in the light. Reta is still an investigational compound with no approved product and so no monograph, which means the mixed-vial window is the general peptide guidance rather than a compound-specific figure.
Findings
- Reta is a 39-amino-acid peptide built on a GIP backbone and joined to a C20 fatty diacid that binds albumin (Goldney et al., Curr Cardiovasc Risk Rep, 2025).
- A chemical supplier’s data sheet gives the dry powder 2 years at −80 °C and 1 year at −20 °C, sealed, away from moisture and light, under nitrogen.
- Its published sequence contains no methionine, cysteine, asparagine or tryptophan, the residues behind several of the fastest degradation reactions in solution.
- Mixed and refrigerated, reta follows the store’s general window: 8 to 12 weeks, fading from around week 6.
How long does reta powder last?
The freeze-dried cake is the stable form. One reagent supplier lists it at 2 years at −80 °C and 1 year at −20 °C, and its storage line is stricter than most: sealed, away from moisture and light, under nitrogen (MedChemExpress, data sheet HY-P3506). In practice that means the vial stays capped and boxed until it is needed, in the fridge for near-term work or the freezer for longer holds. A cold vial is brought to room temperature before opening so that moisture does not condense on the cake. The 10 mg, 20 mg and 30 mg vials are handled the same way.
How long does reta last after mixing?
At 2 to 8 °C, in the dark, opened only through a swabbed stopper, reta lasts 8 to 12 weeks, with quality beginning to drop at around week 6. That matches the table in how long peptides last after mixing. Because no manufacturer or published stability figure exists for a reconstituted solution, this is handling guidance, not an expiry date. There is no dedicated reta reconstitution page; the method is in the general reconstitution guide, and the peptide calculator handles the concentration arithmetic.
What the structure suggests
Peptides in water break down mainly through oxidation of methionine, cysteine and tryptophan and through deamidation of asparagine and glutamine (Manning et al., Pharm Res, 2010). Reta’s sequence avoids most of those weak points: it has none of the first four, and two glutamines, at positions 3 and 19. It also contains non-standard residues, aminoisobutyric acid and an alpha-methyl leucine. Its three tyrosines can still oxidise under light, and like any peptide solution it is swirled rather than shaken, because agitation at the air-water surface promotes aggregation. These are inferences from the structure, offered to explain the guidance, not measured shelf lives.
How long does reta last at room temperature?
There is no published room-temperature figure for reta in solution, and the store’s guidance is that a mixed vial comes out of the fridge only for handling. Warmth speeds every degradation reaction; a 1991 study of a different peptide family held in solution at 37 °C showed how quickly a single weak residue can control a peptide’s half-life on the bench (Friedman et al., Int J Pept Protein Res). A mixed vial left warm for hours or days is best treated as suspect.
Can reta be frozen?
The powder can, and the supplier figures above are freezer figures. A mixed working vial should not be: freezing and thawing aggregates peptides in solution, and repeated cycles compound the damage. Laboratories that need a longer hold freeze single-use aliquots once and thaw each one only when it is needed.
How can you tell mixed reta has degraded?
- Persistent haze. Brief cloudiness straight after mixing can settle within 10 to 15 minutes; haze that remains or returns is aggregation.
- Visible particles or strands floating or settled at the bottom.
- Yellowing or any tint. A freshly mixed vial is clear and colourless.
- Thickening or gel, explained in why peptides gel or go cloudy.
- Past week 12 in the fridge, whatever it looks like.
Travelling with reta
Sealed vials of powder are the easiest form to move. A mixed vial goes in an insulated case with a cold pack, upright and wrapped so that the pack never touches the glass and freezes the solution. The peptide travel case is designed for this. Reta is supplied as lyophilised vials only; there is no nasal spray.
Reta storage at a glance
| State | Where | How long |
|---|---|---|
| Powder, sealed | −20 °C, dark, dry | 1 year (supplier data sheet) |
| Powder, sealed | −80 °C | 2 years (supplier data sheet) |
| Mixed with bacteriostatic water | 2 to 8 °C, dark | 8 to 12 weeks, fading from around week 6 (store guidance) |
| Mixed, room temperature | Handling only | No published figure |
| Mixed, frozen | Single-use aliquots only | Never refreeze a working vial |
The 28 days often quoted for opened vials is a pharmacy beyond-use convention from USP General Chapter 797, built around sterility after repeated entry rather than peptide chemistry. Certificates of analysis are on the lab reports page, and orders ship from within Canada by Canada Post Xpresspost.
Reta is an investigational compound supplied by Vistara Labs for laboratory research use only. The windows on this page describe how long a solution stays in good condition.
Frequently asked questions
How long does reta (GLP-3) last in the fridge after mixing?
Under Vistara Labs’ handling guidance, 8 to 12 weeks at 2 to 8 °C in the dark, with quality beginning to drop at around week 6.
Can reta be left at room temperature?
No published figure exists for reta in solution at room temperature. A mixed vial is kept in the fridge and taken out only for handling.
Can you freeze reta?
The sealed powder can be frozen; one supplier lists 1 year at −20 °C. A mixed working vial should not be frozen, because freeze-thaw cycles aggregate peptides in solution.
Does reta go bad?
Yes. In solution it slowly loses quality, faster with heat, light or agitation. Lasting cloudiness, particles, a colour change or gel mean it has degraded.
How long does reta last in the body?
In a phase 1 study in healthy participants, the mean half-life was about six days (Coskun et al., Cell Metab, 2022).
Handling windows: Vistara Labs, October 2026. Sources: Goldney J et al. Triple agonism based therapies for obesity. Curr Cardiovasc Risk Rep. 2025. PMID 40741227. Coskun T et al. Cell Metab. 2022;34(9):1234-1247. PMID 35985340. Manning MC et al. Stability of protein pharmaceuticals: an update. Pharm Res. 2010. PMID 20143256. Friedman AR et al. Degradation of growth hormone releasing factor analogs in neutral aqueous solution is related to deamidation of asparagine residues. Int J Pept Protein Res. 1991. PMID 1904406. MedChemExpress. Data sheet HY-P3506, sequence and storage. PDF. USP General Chapter 797, beyond-use dating.
More on this: How Long Do Peptides Last After Mixing?
All products supplied by Vistara Labs are intended for laboratory research use only. They are not drugs, are not approved for human or veterinary use, and are not intended to diagnose, treat, cure or prevent any condition. Nothing on this page constitutes medical advice or guidance for use in humans.
