The quantity of sterile diluent (typically bacteriostatic water) added to a vial of lyophilized peptide to create an injectable solution. The reconstitution volume directly determines the peptide concentration: adding 2 mL of water to a 5 mg vial produces 2.5 mg/mL; adding 1 mL produces 5 mg/mL.

Choosing the right reconstitution volume involves balancing precision (larger volumes make small doses easier to measure accurately with standard insulin syringes) against practicality (larger volumes mean more liquid per injection). Published research protocols specify their reconstitution volumes; community protocols vary. Once reconstituted, most peptides must be refrigerated at 2–8°C (35–46°F) and used within a defined timeframe, typically 2–4 weeks.