How do you calculate peptide dosage?

Divide the peptide mass in the vial by the volume of bacteriostatic water added to get the concentration, then divide the amount you want to measure by that concentration to get the volume to draw. A 10 mg vial reconstituted with 2 mL gives 5 mg/mL (5,000 mcg/mL). Measuring 250 mcg is 250 ÷ 5,000 = 0.05 mL, which is 5 units on a U-100 insulin syringe.

How much bacteriostatic water should I add to a 10mg vial?

There is no single correct volume — the water sets the concentration only, never the amount of peptide. Most laboratory work uses 1 mL to 3 mL for a 10 mg vial because those volumes land measurements on readable syringe graduations. With 2 mL the concentration is 5 mg/mL; with 1 mL it is 10 mg/mL and every measured volume halves.

How many units is 250mcg on an insulin syringe?

It depends entirely on concentration, because a syringe unit is a volume and not a mass. On a U-100 syringe one unit is 0.01 mL. At 5,000 mcg/mL (10 mg in 2 mL) 250 mcg is 0.05 mL, or 5 units. At 2,500 mcg/mL (5 mg in 2 mL) the same 250 mcg is 0.10 mL, or 10 units.

Does adding more bacteriostatic water make the dose weaker?

No. Adding more diluent spreads the same total peptide through a larger volume, so the solution is less concentrated and you draw a larger volume for the same measured amount. The amount of peptide per measurement is unchanged, and the total peptide in the vial is unchanged.

How should a peptide be stored after reconstitution?

Once in solution a peptide is far less stable than the dry lyophilised powder. Reconstituted vials are typically kept refrigerated at 2–8 °C, protected from light, and labelled with the date and calculated concentration. Bacteriostatic water contains 0.9% benzyl alcohol, which suppresses microbial growth and is why it is preferred over plain sterile water for vials that are entered more than once.

Can this calculator be used for blends such as GLOW or KLOW?

Calculate each compound in a blend separately using its own mass in the vial. A blend shares one diluent volume across several compounds, so each has its own concentration and a single combined figure would be misleading.

Peptide Reconstitution Calculator

Q: How do I read units on a U-100 insulin syringe?

A U-100 syringe is graduated so 100 units equals 1 mL, making one unit 0.01 mL. A 0.3 mL barrel therefore tops out at 30 units, a 0.5 mL barrel at 50 units, and a 1.0 mL barrel at 100 units. Smaller barrels spread the same scale over a longer distance, so they are easier to read for small volumes.

Enter the peptide mass in the vial, the volume of bacteriostatic water being added, and the amount to be measured. The calculator returns the concentration in mg/mL and mcg/mL, the volume per measurement, the exact units to draw on a U-100 insulin syringe, and how many measurements the vial yields. Free, no sign-up, for laboratory research planning only.

Worked example — BPC-157 10 mg, 2 mL bacteriostatic water, 250 mcg

Concentration: 10 mg ÷ 2 mL = 5 mg/mL, which is 5,000 mcg/mL.
Volume per measurement: 250 mcg ÷ 5,000 mcg/mL = 0.05 mL.
Units to draw: 0.05 mL × 100 = 5 units on a U-100 insulin syringe — the 5 tick mark on a 0.5 mL (50 unit) barrel.
Measurements per vial: 10 mg ÷ 0.25 mg = 40.

The tool loads with these numbers already applied. Change any input and every figure recalculates.

How peptide reconstitution works

Research peptides ship as a lyophilised (freeze-dried) powder because the dry state is far more stable than a solution. Reconstitution is the step of dissolving that powder in a sterile diluent — almost always bacteriostatic water — so the material can be measured accurately in small, repeatable volumes.

Three numbers drive everything: the mass in the vial, the diluent volume, and the amount to be measured. Concentration is mass ÷ volume. The volume to draw is amount ÷ concentration. Everything the calculator shows is a rearrangement of those two lines of arithmetic.

How to read units on a U-100 insulin syringe

Insulin syringes are marked in "units", not millilitres. On a U-100 scale, 100 units = 1 mL, so one unit is 0.01 mL. The three common barrels all use that same scale and differ only in capacity: a 0.3 mL barrel ends at 30 units, a 0.5 mL barrel at 50 units, and a 1.0 mL barrel at 100 units. Because a smaller barrel spreads the same graduation over a longer distance, a 0.3 mL syringe is markedly easier to read for very small volumes.

A unit is a volume, not a mass. Ten units of a 2,500 mcg/mL solution is 250 mcg; ten units of a 10,000 mcg/mL solution is 1,000 mcg — four times as much material for the identical tick mark. Never carry a unit figure across from one reconstitution to another. Recalculate whenever the vial mass or the diluent volume changes, and cross-check the millilitre figure the calculator shows alongside the unit count.

Why water volume changes concentration but never the total peptide

A 10 mg vial contains 10 mg whether 1 mL or 5 mL of bacteriostatic water is added. What the diluent changes is how densely that mass is distributed. At 1 mL the solution is 10 mg/mL and a 0.5 mg measurement is 5 units; at 5 mL the same vial is 2 mg/mL and the same 0.5 mg measurement is 25 units. The measured amount is identical in both cases — only the liquid volume carrying it differs.

This is why "more water makes it weaker" is a misreading. More water makes the solution less concentrated, which means a larger draw for the same amount. Choosing a diluent volume is really about landing measurements on clean, readable tick marks: 0.037 mL cannot be drawn accurately, 0.05 mL can.

Storage after reconstitution

Dry lyophilised material is typically held frozen and is stable for long periods. Once in solution the picture changes: reconstituted vials are generally refrigerated at 2–8 °C, kept away from light, and treated as short-lived. Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which is why it is the standard diluent for a vial that will be entered several times; plain sterile water has no preservative and is normally reserved for single-draw work.

Label the vial with the date and the concentration the calculator gives you. Concentration is the one number that cannot be recovered later by looking at the vial. See the storage and handling guide and the COA library for compound-specific reference material.

Common reconstitution mistakes

Confusing mcg and mg. One milligram is 1,000 micrograms. Vials are labelled in mg while protocols are often written in mcg, and a decimal slip here is a 1,000× error. The unit toggle above converts either way and shows both.
Reusing a unit count after changing the diluent volume. A unit is a volume. Change the water and every unit figure changes with it.
Assuming every syringe is U-100. U-40 barrels are graduated at 40 units per mL, so the same 0.10 mL reads as 4 units instead of 10 — a 2.5× discrepancy in the number, for identical liquid.
Adding diluent straight onto the powder cake, or shaking. Run the water down the vial wall and swirl gently. Peptides are long chains that mechanical agitation can damage.
Picking an awkward diluent volume. If the result lands between graduations, adjust the water volume until measurements sit on a whole tick mark.
Treating a blend as one compound. Each compound in a GLOW or KLOW style blend has its own mass and therefore its own concentration in the shared diluent.

Presets from our catalog

Each preset above fills the calculator with a common laboratory setup for that compound. The product pages carry full specifications, purity data, and batch certificates.

Frequently asked questions

Research use only

All products and tools referenced on this page are supplied strictly for laboratory and research use only. Nothing here is medical advice, a dosing recommendation, or an instruction for administration. Products are not for human or veterinary consumption, diagnosis, treatment, or prevention of any disease. This calculator performs arithmetic on the values entered and makes no judgement about whether those values are appropriate.

Reconstitution calculator

Catalog presets — one click fills the form; the product link opens the compound page.

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Peptide amount in vial (mg)

Bacteriostatic water to add (mL)

Desired dose

Syringe type

Units to draw

units on a U-100 0.5 mL syringe · 0.05 mL

U-100 0.5 mL barrel · marked at 5.0 units

Concentration: 5 mg/mL; 5,000 mcg/mL
Volume per dose: 0.05 mL; 5 units
Dose entered: 0.25 mg; 250 mcg
Doses per vial: 40; whole and partial draws

This calculator performs arithmetic on the values you enter. It is not medical, dosing, or administration guidance. For laboratory and research use only — not for human or veterinary use.