Reconstitution Calculator

Reconstituting peptides means mixing a freeze-dried (lyophilized) powder with bacteriostatic water to create an injectable solution. Getting the right concentration is critical — too little water and each dose becomes difficult to measure accurately; too much water and you'll need to inject uncomfortably large volumes.

This calculator takes three inputs — your vial size (how many milligrams of peptide), how much bacteriostatic water you add, and your desired dose per injection — and tells you exactly how many units to draw on your syringe. It also shows how many doses you'll get from a single vial, helping you plan your supply.

For example, if you have a 5 mg vial of BPC-157 and add 2 mL of bacteriostatic water, your concentration is 2,500 mcg per mL. For a 250 mcg dose, you would draw 0.10 mL, which equals 10 units on a standard 1 mL (100-unit) insulin syringe, or 3 units on a 0.3 mL (30-unit) syringe.

Insulin syringes come in three standard sizes, and choosing the right one matters for accuracy. A 0.3 mL (30-unit) syringe is the most precise for small peptide doses — each tick mark represents just 0.5 units, making it easier to measure doses under 250 mcg accurately. A 0.5 mL (50-unit) syringe offers a good balance between precision and volume. A 1.0 mL (100-unit) syringe handles larger volumes but each tick mark represents a full unit, which can make very small doses harder to measure precisely.

As a general rule: if your draw volume is under 0.15 mL, use a 30-unit syringe. For 0.15–0.30 mL, a 50-unit syringe works well. For anything above 0.30 mL, a 100-unit syringe is appropriate. The most commonly used needle gauge for peptide injections is 29G or 31G — thin enough to be nearly painless for subcutaneous (under the skin) injection.

The amount of bacteriostatic water you add determines the concentration of your solution, and there's no single "correct" amount — it depends on your dose and syringe size. The goal is to create a concentration where your per-dose draw volume falls comfortably within your syringe's measurable range.

Common starting points: For a 5 mg vial, 1–2 mL of water is typical. For a 10 mg vial, 2–3 mL is common. Adding more water makes each dose easier to measure (larger draw volume = more precision), but means you'll be injecting more fluid per dose. Adding less water creates a more concentrated solution with smaller injection volumes, but requires more precise measurement.

Once reconstituted, store the vial in the refrigerator (not the freezer). Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which keeps the solution sterile for approximately 28 days after first puncture. Always use a fresh alcohol swab to clean the vial's rubber stopper before each draw.

Spraying water directly onto the powder. Always aim the stream of bacteriostatic water against the inside wall of the vial, letting it trickle down gently. Blasting the lyophilized cake directly can damage peptide bonds and reduce potency.

Shaking the vial. Never shake a reconstituted peptide — this creates foam, denatures the protein, and reduces effectiveness. Instead, gently swirl or roll the vial between your palms until the powder fully dissolves. Some peptides dissolve instantly; others can take 5–10 minutes.

Using the wrong water. Always use bacteriostatic water (BAC water) — not sterile water, saline, or tap water. Sterile water lacks preservative and must be used within 24 hours. BAC water's benzyl alcohol preservative allows multi-dose use over several weeks.

Confusing mg, mcg, and units. 1 mg = 1,000 mcg. Syringe "units" refer to the markings on insulin syringes (100 units = 1 mL). These are different measurement systems, and mixing them up is the most common dosing error. This calculator handles all the conversions for you.