Lyophilised powder is stable; solution is not
Peptides ship freeze-dried because in that state they tolerate room temperature for weeks and refrigeration for years. The moment you add liquid, degradation begins — hydrolysis, oxidation and aggregation all accelerate in solution.
As a rule of thumb: unopened powder in the freezer keeps for a year or more, refrigerated reconstituted peptide keeps around four weeks, and anything left at room temperature in solution should be considered degraded within days.
Reconstitution basics
Bacteriostatic water — sterile water with 0.9% benzyl alcohol — is the standard diluent because the preservative allows multiple withdrawals from one vial. Plain sterile water is single-use only.
Aim the stream of water at the glass wall of the vial rather than directly at the powder, and let it dissolve on its own. Never shake: agitation shears peptide chains and causes aggregation. Swirl gently if you must.
Working out concentration
Concentration is simply the peptide mass divided by the volume of water added. A 5 mg vial reconstituted with 2 ml gives 2500 mcg/ml, so a 250 mcg dose is 0.1 ml — ten units on a standard 100-unit insulin syringe.
Always calculate before you draw, and write the concentration and reconstitution date on the vial with a marker.
Signs a vial has gone bad
Discard rather than gamble if you see any of these:
- Cloudiness, floating particles or stringy strands in a solution that was clear
- Discolouration (GHK-Cu is legitimately blue; most others should be colourless)
- A cake of powder that has visibly melted, browned or shrunk before reconstitution
- Any vial past four weeks in the fridge, or one that spent hours warm