Follow the label for the exact product, because the labels differ in ways that matter. Reconstituting means adding a liquid, called the diluent, to a freeze-dried powder so it can be injected. FDA-approved peptide labels agree on a few steps: use the named diluent, mix gently without shaking, and inject only a clear solution. They disagree on what comes after, including whether the mixed vial can be kept at all.
This page sets out what two approved labels instruct, and what the diluent label itself says. It gives no volumes or doses of its own. Research-only peptides such as BPC-157 have no approved label, so there are no official instructions for them to follow.
Why peptides come as powder
Protein and peptide drugs are prone to both chemical and physical instability, and a standard review of the field treats stabilization in the dried state as one of the main routes to a stable product [1]. The trade-off is that the powder must be turned back into a solution before use, and every step of that process, from the choice of liquid to how hard the vial is agitated, can affect what ends up in the syringe.
Step one: the diluent the label names
The label for EGRIFTA SV, a tesamorelin product, is explicit: use only the diluent provided, which is Sterile Water for Injection, and add 0.5 mL to one vial [2]. The label for GENOTROPIN, a somatropin product, takes a different route entirely. Its powder and a diluent containing metacresol as a preservative sit in the two chambers of one cartridge, and a pen device mixes them [3].
Bacteriostatic water, sterile water preserved with benzyl alcohol, is labeled only for diluting or dissolving drugs “according to instructions of the manufacturer of the drug to be administered” [4]. In other words, the drug’s label decides which liquid is correct, not the liquid’s. The differences between the two waters are covered in bacteriostatic water for peptides.
Step two: mix gently, do not shake
The EGRIFTA SV label says to mix by rolling the vial gently in the hands for 30 seconds, and states plainly: do not shake [2]. The GENOTROPIN label also says do not shake, and its pen mixes the two chambers when the parts are screwed together gently with the pen held upright [3]. Neither label gives its reason, but the likely one is physical. For protein drugs such as antibodies, agitation at the air-liquid surface is one of the common stresses that makes molecules clump into aggregates, and a review of that work notes aggregates may reduce activity and could provoke immune responses [6].
Step three: look before injecting
Both labels require a visual check. EGRIFTA SV is to be used only if the solution is clear, colorless and free of particles [2]. GENOTROPIN must not be injected if the solution is cloudy or contains particles [3]. The bacteriostatic water label adds the same check for anything dissolved in it: inspect for clarity and for unexpected precipitation or discoloration [4].
Where the powder comes from matters too
Careful mixing cannot fix a contaminated ingredient. In August 2026 the FDA reported at least 30 patients with reactions, including fever, chills and sepsis-like symptoms, after injections compounded from glutathione labeled as dietary supplement grade [5]. The agency reminded compounders that supplement-grade ingredients are not appropriate for injectable drugs. That episode is read in full in glutathione injections: the evidence.
Once a vial is mixed, where it goes matters as much as how it was prepared; the labeled sites are covered in peptide injection sites. For a prescriber-directed product, the pharmacist or prescriber who dispensed it is the right person to confirm any step the label leaves unclear.