Most research peptides arrive as a freeze-dried powder that has to be dissolved before it can be measured and injected. This is called reconstitution, and it is simpler than it sounds. Here is exactly how to do it, the one piece of math that matters, and the mistakes that ruin a vial.
Short version: Add bacteriostatic water to the powder vial slowly, down the inside wall, then swirl gently until it dissolves. Never shake. The amount of water you add sets the concentration, which decides how far you draw the syringe. Our reconstitution calculator does that math for you.
What you need
- Bacteriostatic water (BAC water): sterile water with 0.9% benzyl alcohol that suppresses bacterial growth, so the vial stays usable across multiple draws. Not the same as sterile saline or plain sterile water.
- The peptide vial: the lyophilised powder, with its total amount printed on the label (commonly 5 mg or 10 mg).
- Insulin syringes: 1 mL / 100-unit (U-100) syringes are standard.
- Alcohol swabs for the vial tops.
Step by step
- Clean the tops. Wipe both the BAC water and peptide vial stoppers with an alcohol swab and let them dry.
- Draw your water. Decide how much BAC water to add (see the math below), and draw that volume into the syringe.
- Add it slowly. Insert the needle into the peptide vial and angle it so the stream runs down the inside wall of the glass, not directly onto the powder cake. Blasting the powder can damage it.
- Swirl, do not shake. Once all the water is in, roll or swirl the vial gently until the powder fully dissolves. Shaking or vortexing creates foam and can break the peptide apart.
- Label and store. Write the date on the vial and refrigerate it. That is your reconstitution date, and it tells you how long the solution has been in use.
The only math that matters
Concentration is just the amount of peptide divided by the water you added:
Concentration = peptide amount ÷ water volume. Example: a 10 mg vial with 2 mL of BAC water gives 5 mg/mL. The more water you add, the more dilute the solution, and the larger the volume you draw for the same dose.
Your dose is fixed by the protocol; the number of syringe units you draw depends entirely on this concentration. If mixing “mg” and “units” is confusing, read how peptide doses work, or just enter your numbers into the calculator and it will show the exact unit mark, with a syringe diagram.
Storage after mixing
A reconstituted vial is far more delicate than the dry powder. Keep it refrigerated at 2 to 8°C, away from light, and most peptides are used within about four weeks. Do not freeze a reconstituted vial unless the specific peptide’s guidance says to. The unmixed powder is much more stable and can often be kept frozen long-term.
Common mistakes
- Shaking the vial. The single most common error. Swirl gently instead.
- Using the wrong water. BAC water, not tap, saline, or plain sterile water, for a multi-use vial.
- Assuming “units” equals “dose.” They are different measurements. Always convert through your concentration.
- Not labelling the date. Without it you lose track of how old the solution is.
Next steps
Every peptide profile on this site lists a suggested dilution and links to the calculator preloaded for that compound. Start with the fundamentals in Peptides 101, or jump to a specific profile like BPC-157 or semaglutide.
This article is educational and reference-only. It is not medical advice. Research peptides are not approved for human use in most jurisdictions; follow all applicable laws and consult a qualified professional.
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