How to mix bacteriostatic water with a lyophilised peptide vial — the right ratio, the right technique, and the small mistakes that ruin a vial before you’ve drawn a single dose.
What “reconstitution” actually means
Research peptides arrive as a freeze-dried (lyophilised) powder sitting at the bottom of a glass vial. You can’t draw powder into a syringe. So before you can dose, you need to dissolve the powder back into a liquid by adding bacteriostatic water through the rubber stopper. That’s reconstitution.
The peptide’s weight in mg doesn’t change. You’re just choosing how much liquid to dilute it into — and that choice sets the concentration of every dose you’ll ever draw from the vial.
What you need before you start
- The peptide vial — sealed, label intact, stored as the supplier instructed.
- Bacteriostatic water — a multi-dose vial (usually 10 or 30 mL) containing water with 0.9% benzyl alcohol as a preservative.
- A drawing syringe — most researchers use an insulin syringe (U-100, 1 mL) or a small luer-lock for larger transfers.
- Alcohol swabs — for the rubber stopper of both vials.
- Sharps bin — used needles never go in household waste.
Choosing your BAC water volume
This is the single most important decision in reconstitution. There’s no universally “correct” volume — it’s a trade-off between three things: how easy doses are to measure, how concentrated each draw is, and how long the vial lasts before you exceed its shelf-life window.
| If you add this much BAC water to a 5 mg vial | Concentration | 250 µg dose draw |
|---|---|---|
| 1 mL | 5 mg / mL | 5 units on a U-100 insulin syringe |
| 2 mL | 2.5 mg / mL | 10 units |
| 3 mL | 1.67 mg / mL | 15 units |
| 5 mL | 1 mg / mL | 25 units |
Rule of thumb: aim for a draw between 10 and 30 units on a U-100 syringe. Too few units (under 5) and small measurement errors swing the dose dramatically; too many (over 50) and you may need to draw twice.
Step-by-step reconstitution
- Wash your hands and set up on a clean surface. A kitchen counter you’ve just wiped down is fine. You don’t need a sterile lab — but you do want to avoid loose hair, food crumbs, or pet dander near open vials.
- Swab both stoppers. Wipe the rubber stopper of the BAC water vial and the peptide vial with an alcohol pad. Let them air-dry for 10–15 seconds.
- Draw the calculated BAC water volume. Pull the syringe plunger to the volume mark, push the needle straight down through the BAC water stopper, invert, and draw the water. Push out any large air bubbles by tapping the barrel.
- Inject the BAC water down the side of the peptide vial. Angle the needle so the water runs down the glass wall, not directly onto the powder. The peptide is fragile — splashing it with a hard stream can denature some of it.
- Swirl, don’t shake. Gently roll or swirl the vial between your palms for 20–30 seconds until the powder fully dissolves. Shaking creates foam and may damage the peptide structure.
- Inspect. The liquid should be clear and colourless. Cloudiness, particles, or sediment that won’t dissolve are signs to stop and contact the supplier.
- Label the vial. Write the date of reconstitution and the concentration on the vial or its cap with a fine-point permanent marker. Future you will not remember.
Common mistakes
After reconstitution: storage & shelf life
Once mixed, store the vial in the refrigerator at 2–8°C. Most reconstituted peptides remain stable for 28 days when preserved with bacteriostatic water; some shorter, some longer — check the compound page for the specific peptide for its shelf-life guidance.
If you used sterile water rather than BAC water, your window drops to 24–48 hours. Discard at the end of that window and don’t try to extend it.
Never freeze a reconstituted vial. Freezing forms ice crystals that physically break peptide bonds. If you need to store long-term, leave the powder unmixed and freeze the dry vial instead.