May 22, 2026
BAC Water Storage, Expiry, and Safety: What Every Peptide User Should Know
Bacteriostatic water is not sterile forever. Learn how to store it, when to replace it, and what to do if you suspect contamination.
Bacteriostatic water (BAC water) is the standard diluent for peptide injections. It contains 0.9% benzyl alcohol, which inhibits bacterial growth — but it is not a magic bullet. Mismanagement of BAC water is one of the most common sources of injection-related infections.
How long does BAC water last?
| Container type | Shelf life after opening |
|---|---|
| 30 mL multi-dose vial | 28 days |
| 10 mL multi-dose vial | 28 days |
| Single-dose ampoule | Use immediately, discard remainder |
The 28-day rule comes from USP <797> standards for sterile compounding. After 28 days, the risk of microbial contamination increases even with benzyl alcohol preservative.
Storage tips
- Refrigerate — 2°C to 8°C (36°F to 46°F). Do not freeze.
- Keep in original vial — Do not transfer to another container.
- Wipe the stopper — Use a fresh alcohol swab before each draw.
- Use a new needle each time — Never reuse a needle to draw BAC water.
- Visual check — If the water looks cloudy or has floating particles, discard immediately.
Signs of contamination
- Cloudiness or turbidity
- Floating particulates
- Unusual odour
- Visible mould (rare but possible)
What if you used contaminated BAC water?
If you or someone you know injected peptide reconstituted with water past its 28-day mark or showing signs of contamination:
- Monitor the injection site for redness, swelling, warmth, or pain.
- Watch for systemic signs: fever, chills, malaise.
- Contact a healthcare provider immediately if any signs appear.
Track it in TrackPep
TrackPep's inventory module lets you log BAC water bottles with expiry dates, so you always know when it is time to replace. No more guessing.