Guide
Bacteriostatic water, from the box to the syringe
Every compounded peptide starts as a powder, and bacteriostatic water is what turns it into something you can draw and inject. This guide explains what the water actually is, what reconstitution means, the one piece of math that decides your syringe units, and how to store both the bottle and the mixed vial.
What bacteriostatic water is
Bacteriostatic water is sterile water with 0.9 percent benzyl alcohol added as a preservative. The preservative is the entire point: it suppresses bacterial growth inside the bottle, which is what makes it safe to puncture the same stopper again and again over several weeks. Plain sterile water has no preservative, which is why it is meant for one use and done.
What reconstitution is
Peptides are fragile molecules, so pharmacies ship them freeze-dried: a small white puck or powder in a sealed vial, stable at room temperature during transit. Reconstitution is the step where you add bacteriostatic water to that powder and it becomes a clear solution you can measure with a syringe. Nothing about the peptide changes; it simply goes from a form that ships well to a form you can draw.
The one piece of math that matters
The water you add sets the concentration. The dose is set by your prescriber. Those are two different numbers, and the syringe units you draw are just the bridge between them. Same vial, two different mixes:
| Vial | Water added | Concentration | Prescribed dose | Draw |
|---|---|---|---|---|
| 5 mg | 2 mL | 2.5 mg per mL | 0.25 mg | 10 units |
| 5 mg | 1 mL | 5 mg per mL | 0.25 mg | 5 units |
Both rows deliver exactly the same dose. The only difference is how much of the syringe it occupies, and a bigger draw is simply easier to read against the markings. This is the arithmetic Steady’s reconstitution calculator does for you: enter the vial strength and the dose your prescriber wrote, and it suggests the water, draws the fill line on a picture of your syringe, and saves the mix. The reverse check always works: units times concentration, divided by 100, must land back on the prescribed dose, and the doses in a vial must add up, a 10 mg vial at 2 mg per dose is exactly five. It computes; it never chooses the dose.
Mixing, as it is commonly done
- Wipe both stoppers
An alcohol swab across the water bottle and the peptide vial before any needle touches them.
- Add the water slowly, against the glass
Draw the chosen amount of bacteriostatic water and ease it down the inside wall of the vial rather than jetting it straight into the powder. The stream matters because force creates foam.
- Swirl, never shake
A gentle swirl and patience. Most peptides dissolve clear within a few minutes on their own.
- Check it, then log it
The solution should be clear, no particles, no cloudiness. Log the mix in Steady and the vial starts its 28-day countdown with the doses-remaining math attached.
Storing it
| What | Where | How long |
|---|---|---|
| Bacteriostatic water, unopened | Room temperature, away from light | The printed expiration date |
| Bacteriostatic water, opened | Room temperature, away from light | 28 days after first puncture, by convention |
| Peptide vial, still powder | Cool, dark, or refrigerated per the label | The pharmacy’s date |
| Peptide vial, mixed | Refrigerator, 36 to 46°F | About 28 days, most protocols |
Two rules carry most of the weight: once mixed, it lives in the refrigerator, and it never goes in the freezer, because freezing wrecks the peptide. Steady’s supply screen keeps the clock for you, days since mixing and doses left, and PEPAI answers storage questions on the spot.
Common questions
- How much bacteriostatic water do I add to a vial?
- Steady answers this for you. Enter the vial strength and your prescribed dose, and the calculator suggests a water amount that lands the dose on a clean, easy-to-read number of syringe units; you can override it. There is no single fixed answer because water sets the concentration, not the dose: more water simply spreads the same dose across more units.
- How do I know the draw is actually my dose?
- Two checks close the loop. Units times concentration, divided by 100, must equal the dose: 10 mg mixed with 2 mL is 5 mg per mL, so a 40-unit draw is 0.4 mL, which is 2 mg. And the vial must add up: a 10 mg vial at 2 mg per dose is exactly 5 doses, so a vial emptying faster or slower than that means an input is wrong. Steady runs both and shows doses remaining per vial.
- Can I use plain sterile water instead?
- Plain sterile water has no preservative, so it is made for single use, not for a vial you will puncture repeatedly over weeks. Which diluent your prescription expects is a pharmacy question, and worth asking them directly.
- How long does a mixed vial last?
- Most protocols treat 28 days in the refrigerator as the working shelf life, which is the same window Steady’s supply screen counts down. After that, the preservative is no longer trusted to keep up with repeated punctures.
- Does the bacteriostatic water bottle itself expire?
- It carries a printed expiration date unopened, and once the stopper has been punctured the same 28-day convention applies to the bottle too.
- Why should the vial never be shaken?
- Peptides are fragile chains. Shaking whips air through the solution and can damage them; a foamy or cloudy vial is a bad sign. Swirl gently and let it dissolve on its own time.
- What if the mixed solution looks cloudy or has particles?
- A properly dissolved peptide solution is clear. Cloudiness, visible particles or discoloration are a stop sign: do not use it, and take the question to the pharmacy that dispensed it.
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Get Steady on the App StoreSteady is a record-keeping and education tool. This page explains supply mechanics in general terms; it is not medical advice, and doses, diluents and schedules belong with your prescriber and pharmacy.