Unopened, lyophilised vials
Before reconstitution, retatrutide is a freeze-dried powder, and it’s the most stable form the peptide will ever be in. Most manufacturer guidance for similar peptides calls for refrigeration at 2-8°C, though some formulations tolerate brief periods at room temperature during shipping. Freezing isn’t generally recommended, since ice crystal formation can damage the peptide structure.
Why lyophilised form is more forgiving
Removing the water from a peptide removes the medium most degradation reactions need to happen in. That’s why powder survives short lapses in refrigeration far better than a reconstituted liquid does.
After reconstitution
Once bacteriostatic water is added, retatrutide becomes far more sensitive to temperature and time. Refrigerated storage at 2-8°C is standard advice once mixed, and most guidance for similar peptides suggests using a reconstituted vial within a limited number of weeks rather than treating it as shelf-stable indefinitely.
Keeping it out of light too
Peptides are also broken down by light exposure over time, which is why vials typically come in amber or opaque packaging and are best kept away from direct sunlight even while refrigerated.
A simple routine
Refrigerate as soon as a delivery arrives, keep the vial upright, avoid the door shelf where temperature fluctuates most with a fridge opening and closing, and note the reconstitution date on the vial itself so shelf life is easy to track.