How long do reconstituted peptides last?
Short answer: once mixed with bacteriostatic water and refrigerated, most peptides are commonly used within about 28 days. Before reconstitution, sealed lyophilized vials last far longer. The details — and the tracking — are where people slip.
Not medical advice. This guide covers logistics and tracking mechanics only. Doses, compounds, and protocols belong in a conversation with a licensed clinician.
Why ~28 days?
Bacteriostatic water contains 0.9% benzyl alcohol, which suppresses bacterial growth across repeated needle punctures of a multi-dose vial — and 28 days is the standard window pharmacies apply to multi-dose vials opened with bacteriostatic preservative. Peptide stability varies by compound (some degrade faster in solution), but the 28-day convention is the common operating rule. Your supplier's storage guidance and your clinician outrank any rule of thumb.
Storage that protects the vial
- Refrigerate after reconstitution (2–8 °C). Don't freeze a mixed vial — ice crystals shear peptide chains.
- Keep it dark. Light degrades many compounds; the fridge door shelf in original packaging works.
- Swab the stopper before every draw. The preservative buys margin; it isn't an excuse for sloppy technique.
- Watch for cloudiness or floaters. A clear solution turning cloudy is a discard signal regardless of the calendar.
The math of not wasting vials
Vial waste usually isn't spoilage — it's arithmetic. A 5 mg vial at 250 mcg per day holds 20 doses: finished in 20 days, comfortably inside the window. The same vial at 100 mcg every other day is a 100-day supply in a 28-day container. Running the numbers before mixing (the calculator shows doses-per-vial) tells you whether to reconstitute the whole vial at all.
Track the date or lose the date
The failure mode is universal: a vial with a smudged label and a vague memory of “a couple weeks ago.” A tracker that stamps the reconstitution date, counts days automatically, and warns near the mark removes the entire category of doubt.
Every vial gets a day counter
PepShot starts counting the day you reconstitute, shows “Day 12” on the vial card, and flags anything approaching the 28-day mark.
Download PepShotRelated: how to reconstitute · reconstitution calculator