How long does BAC water and reconstituted peptide last?
Unopened bacteriostatic water lasts until its printed expiry. Once a multi-dose vial is opened, it is commonly dated and discarded within about 28 days. How long a reconstituted peptide lasts depends on the compound and its formulation, so follow the instructions that came with your product rather than a general figure. Many products say to keep mixed vials cold and out of light, and to set aside any solution that turns cloudy or develops particles, follow the instructions that came with yours.
Shelf life at a glance
| State | How long it keeps | Storage |
|---|---|---|
| Unopened bac water | Until printed expiry | Room temperature, out of light |
| Opened bac water vial | About 28 days once punctured | Refrigerate; date the vial |
| Reconstituted peptide | A few weeks (peptide dependent) | Refrigerate 2 to 8 C, out of light |
| Lyophilized powder | Months to years unopened | Per product label; often cold |
The 28-day window for an opened multi-dose vial reflects standard multi-dose vial guidance. Always defer to the discard date on your own product label.
Refrigeration: helpful, but not a substitute for clean technique
The standard advice is correct: refrigerate reconstituted peptides. Cold storage slows the chemical breakdown of the peptide itself, so a mixed vial stays potent longer in the fridge than at room temperature.
Here is a small thing to know. The preservative in BAC water is benzyl alcohol. It is what fights germs. Germ-fighting works a little slower when it is cold. That does not mean the fridge is bad. It means two things keep your vial safe, not one. The cold keeps the peptide strong. Clean habits keep germs out. You need both.
Clean habits means: wipe the rubber top before each poke, do not touch the needle, and pull the liquid out gently. Use a fresh needle each time, follow the storage instructions that came with your product, and respect the discard date. If the liquid ever looks cloudy, changes color, or has floating bits, throw it out, no matter the date.
Refrigerated shelf life by peptide
Common reconstituted shelf-life windows for popular peptides. These are general guides; confirm against your own product and label the vial with a discard date.
| Peptide | Refrigerated | Note |
|---|---|---|
| BPC-157 | 30 days | Keep in the fridge. Protect from light. |
| TB-500 | 30 days | Keep in the fridge. Larger doses typical. |
| Ipamorelin | 28 days | Keep in the fridge. Consider splitting into smaller batches. |
| Semaglutide | 56 days | Keep in the fridge, following your product's instructions. |
| Tirzepatide | 42 days | Keep in the fridge, following your product's instructions. |
| GHK-Cu | 30 days | Keep in the fridge. Blue tint is normal. |
| Melanotan II | 30 days | Keep in the fridge. Start with a very low test dose. |
| PT-141 | 30 days | Keep in the fridge. |
When to discard a vial
- The solution is cloudy, discolored, or has visible particles.
- It is past the discard date you wrote on the label.
- An opened bac water vial is more than about 28 days old.
- The vial was left unrefrigerated far longer than intended.
- The seal or stopper looks compromised.
Shelf life and storage FAQ
Keep reading
References
Primary sources for the facts on this page. We cite regulatory and peer-reviewed authorities rather than secondary blogs.
- Bacteriostatic Water for Injection, USP - prescribing information · U.S. FDA labeling via DailyMed (NIH / NLM)Defines bacteriostatic water as sterile water with 0.9% benzyl alcohol added as a bacteriostatic preservative, supplied in a multiple-dose container for diluting or dissolving drugs; contraindicated in neonates.
- Preventing Unsafe Injection Practices - multi-dose vials · U.S. Centers for Disease Control and PreventionOnce opened or first punctured, a multi-dose vial should be dated and discarded within 28 days unless the manufacturer specifies otherwise.
- Benzyl alcohol (Compound CID 244) · NIH PubChem, National Library of MedicineChemical identity, properties, and safety data for benzyl alcohol, the bacteriostatic preservative in BAC water.
The Plan Builder calculates your mix date and discard date and prints them on a vial label.