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Peptide Reconstitution: How the Math Works

The arithmetic behind the peptide reconstitution calculator: how vial mass, bacteriostatic water volume, and target dose resolve into a concentration, an insulin-syringe unit count, and a doses-per-vial figure, with the assumptions and limits made explicit.

The formula

Reconstitution math is one division and one unit conversion. The vial holds a known mass of lyophilized peptide. Bacteriostatic water dissolves it to a known volume. Concentration is mass divided by volume.

Concentration (mg/mL)  =  vial mass (mg)        ÷  BAC water (mL)
Dose volume (mL)       =  desired dose (mcg)    ÷  1000  ÷  concentration
Syringe units          =  dose volume (mL)      ×  100
Doses per vial         =  floor( vial mass (mg) ×  1000  ÷  dose (mcg) )

The factor of 100 in the third line is the U-100 insulin syringe convention: one millilitre of solution maps to 100 markings on the barrel. A 0.10 mL injection therefore reads as 10 units. The factor of 1000 in the second line converts the dose from micrograms (the unit users think in) to milligrams (the unit the concentration is in). No other arithmetic is happening on the page.

What goes into the calculator

Three numeric inputs:

  • Vial size (mg): the labelled mass of lyophilized peptide. Common sizes are listed per compound in src/data/compounds/peptides.json (e.g. BPC-157 ships in 5 mg or 10 mg vials; TB-500 in 2 / 5 / 10 mg).
  • Bacteriostatic water (mL): the diluent volume. The calculator does not constrain this; users pick a number that makes the resulting concentration legible on an insulin syringe.
  • Desired dose (mcg): the per-injection dose target.

Four outputs:

  • Concentration in mg/mL: useful for cross-checking against monograph stability ranges.
  • Concentration in mcg per syringe unit: the working number for drawing a dose without doing arithmetic at the bench.
  • Syringe units per dose, rounded to one decimal place because U-100 markings cap there.
  • Doses per vial: floor of total micrograms divided by dose, so partial doses do not count.

Assumptions and limits

The calculator assumes the labelled vial mass is the actual mass of peptide. For research-grade material from a compounding pharmacy with a batch certificate of analysis, this is reasonable. For gray-market lyophilized vials with no third-party HPLC, it is a guess. Independent purity testing of consumer peptide vials has repeatedly found mass deviations and contamination. The math has no way to detect that, and neither does the user.

It assumes the diluent is bacteriostatic water (sterile water containing 0.9% benzyl alcohol), used at standard pharmaceutical concentration. Plain sterile water and saline are physically possible diluents but offer no preservation, so a multi-dose vial reconstituted with either should be treated as single-use. The calculator does not check what the user actually has on hand.

It assumes the reconstituted vial is stored refrigerated at 2–8 °C and consumed within the stability window stated in the compound monograph. For BPC-157, the IdeaVerse-sourced reconstitution note (in peptides.json) is "stable for up to 4 weeks refrigerated." This is a literature-aligned working figure, not a manufacturer guarantee.

It assumes no overage. Real lyophilized vials sometimes contain 5–10% above the labelled mass to compensate for transfer losses; the calculator ignores this and treats the label as exact.

What the calculator deliberately does not do:

  • It does not recommend a dose. The "desired dose" field is an input, not a suggestion.
  • It does not validate compound identity, purity, or potency.
  • It does not substitute for sterile compounding technique, vial-handling hygiene, or any clinical judgement about whether a given compound is appropriate for a given person.

Unit conventions

Three unit pairs cause most reconstitution errors:

  • Milligrams vs micrograms. 1 mg = 1000 mcg. Vials are labelled in mg; community dose discussions are usually in mcg. The calculator keeps the mg input on the vial side and the mcg input on the dose side to mirror that convention.
  • Subcutaneous vs intramuscular. Both routes use the same volume math. Insulin syringes (typically 0.3 mL or 0.5 mL, 29–31 G) are designed for SubQ. IM injection of peptides is uncommon outside specific protocols (e.g. some TB-500 schedules) and uses a larger syringe; the unit-count output still applies if the syringe is U-100 marked.
  • Insulin syringe units vs IU. A "unit" on a U-100 insulin syringe is a volume marking, 1/100 of a millilitre. An "International Unit" (IU) is a mass-equivalent for biologically standardised compounds (insulin, hCG, HGH) and is not interchangeable with syringe units. Conflating the two is one of the more common errors in peptide forums; the calculator only outputs syringe units.

A tuberculin syringe (1 mL, marked in 0.01 mL increments) reads volume directly. To convert syringe units to tuberculin millilitres, divide by 100.

Why this is documentary, not prescriptive

This page describes arithmetic. It does not describe what compound to take, at what dose, for what indication, or whether to take anything at all. The calculator returns a number for the inputs the user provides; the user remains responsible for the inputs.

Compound-specific evidence (what is actually known about efficacy, mechanism, safety, and regulatory status) lives in the research articles. For BPC-157, that is the BPC-157 FDA Category 1 review. For other compounds in the calculator, dosing-frequency and route metadata in peptides.json reflect the IdeaVerse monograph for that compound; the monograph and its citations are the source of truth, not the calculator output.