Reconstitution 101: Turning a Powder Vial Into a Working Dose

Every peptide ships as a lyophilized (freeze-dried) powder in a small vial. Before you can inject or even measure a dose, you need to dissolve it in sterile liquid. That process is reconstitution.

This guide covers everything from picking the right volume of water to the arithmetic that tells you how many units to pull into the syringe.

What you need

• The peptide vial — usually 2mg, 5mg, or 10mg per vial
• Bacteriostatic water (bac water) — sterile water with 0.9% benzyl alcohol as a preservative. Lets you pull multiple doses from the same vial over days/weeks
• An alcohol swab — for both vial stoppers
• A mixing syringe — a 1mL or 3mL slip-tip with a drawing needle (usually 21g) works well
• Your dosing syringe — a 0.3mL or 0.5mL insulin syringe (BD Ultra-Fine 31g is the community favorite)

The one decision that matters: how much bac water

The volume of bac water you add determines your concentration, which determines how many syringe units equal a given dose. There's no "correct" answer — just trade-offs:

• More water (e.g. 5mL in a 5mg vial): easier math, more accurate small doses, larger injection volume
• Less water (e.g. 1mL in a 5mg vial): more concentrated, smaller injection volume, harder to measure tiny doses accurately

Community rule of thumb: aim for a concentration where your typical dose is 10–50 units on a standard 100u insulin syringe. Below 10 units, rounding error gets annoying. Above 50, the injection volume starts feeling big.

The math (once, then never again)

Insulin syringes are marked in "units" where 100 units = 1.0 mL.

Concentration (mcg per unit) = (peptide in vial in mcg) / (bac water in mL × 100)

Example: 5mg (5000 mcg) vial + 2mL bac water = 5000 / (2 × 100) = 25 mcg per unit.

So a 250 mcg dose = 250 / 25 = 10 units on the syringe.

Pick your bac water volume so typical doses fall in that comfortable 10–50 unit range. If you hate math, use the Peppercalc dose calculator — punch in your vial size and desired dose and it spits out the unit count.

Step-by-step

1. Alcohol-swab both vial stoppers (peptide + bac water) and let them dry.
2. Draw bac water into the mixing syringe. Use the amount you decided on above.
3. Slowly inject bac water into the peptide vial — tilt the syringe so the stream runs down the inside wall of the vial, not directly onto the powder. Fast streams aimed at the powder cause foaming, which can damage peptide.
4. Do not shake. Let it sit 30–60 seconds, then swirl gently until the powder fully dissolves. If it doesn't clear in a minute or two, return it to the fridge for 5–10 minutes and swirl again.
5. Label the vial — compound name, concentration (mcg/unit), reconstitution date. Sharpie on the stopper or a small sticker both work.
6. Refrigerate between doses. Most reconstituted peptides are stable 2–4 weeks refrigerated, some up to 8.

Common mistakes

• Shaking the vial. Peptides are sensitive. Swirl, don't shake.
• Injecting water directly onto the powder cake at high speed. Causes foam that can denature the peptide at the water-air interface.
• Forgetting to label. Two weeks in, you will not remember which vial is which concentration. Guessing is how you end up under- or over-dosing.
• Using sterile (not bacteriostatic) water for multi-dose vials. Sterile water has no preservative — it's fine for single-use but a contamination risk for multi-day vials.
• Reconstituting everything at once. Most peptides store longer as powder than in solution. Reconstitute a vial when you're ready to use it, not before.

Storage, quickly

• Powder (unreconstituted): fridge is ideal, but most peptides tolerate room-temp shipping for short periods. Freezer long-term (weeks to months) if you need it.
• Reconstituted: fridge only. Don't freeze — freeze-thaw cycles degrade peptides.
• Stability windows vary by peptide. BPC-157 and TB-500 are relatively hardy (3–4 weeks reconstituted). Growth hormone secretagogues (Sermorelin, Ipamorelin, CJC-1295 no-DAC) degrade faster — treat those as 7–14 day windows.

Where to go next

• For a deeper reference on any specific peptide's stability, check its Pepperpedia entry.
• The math-heavy explanation of dose calculation lives at Peppercalc.
• Post questions about a specific compound's reconstitution in the Beginner Questions forum.