Peptide Reconstitution & Dosage Calculator

What this calculator checks

A reconstitution answer can be arithmetically correct and still impossible to carry out — a draw that does not fit the barrel, a water volume no vial holds, a figure that falls between the marks on a syringe. These are the cases this tool catches and explains instead of handing back a number.

A dose larger than the vial holds

If your dose is bigger than the entire vial contains, you get a plain explanation rather than a number. This is nearly always a microgram/milligram mix-up, and 1 mg = 1000 mcg, so the two are easy to transpose. It is the single most consequential error in reconstitution, because every dose that follows inherits it.

A draw that will not fit your syringe

A 0.3 mL barrel holds 30 units, a 0.5 mL holds 50, a 1 mL holds 100. If your dose needs more than that, the calculator says so and tells you what to change — less bacteriostatic water for a stronger concentration, or a larger syringe — rather than printing a figure you physically cannot draw.

A draw that lands between the marks

Insulin syringes are marked in fixed steps, and the step depends on the barrel: 0.3 mL and 0.5 mL barrels are usually marked in single units, 1 mL barrels every two. When your dose lands between two marks, the calculator says so and shows the nearest mark you can actually draw, instead of implying a precision the syringe does not have. If your 0.3 mL barrel is one of the half-unit versions, switch on “½-unit marks” and every figure adjusts to it.

A water volume you could not measure

Solving for water usually produces a figure like 1.371 mL, and since you add water with a syringe, that is not an instruction anyone can follow. The reconstitution calculator rounds to the nearest 0.05 mL — roughly the finest volume you can measure reliably — and then tells you the draw you genuinely get at that rounded volume, rather than quietly reporting the unreachable one.

A water volume larger than the vial

Arithmetic will happily tell you to add 60 mL of water to a 10 mL vial. When the volume needed to hit your target draw exceeds what a vial realistically holds, the calculator flags it instead of handing back a physically impossible instruction.

The arithmetic itself, shown

Every result can be expanded to show its three steps — concentration, dose volume, then syringe units — worked through with the numbers you entered. You should not have to take a number on faith when the whole point is that it is verifiable.

What the numbers are based on

The arithmetic here needs no authority behind it — concentration is mass divided by volume, and every result expands to show its three steps using the numbers you entered, so you can check it rather than trust it. What does rest on outside standards is the U-100 syringe convention and the diluent. Those are the primary sources for both.

• Giving an insulin injection — MedlinePlus ↗

  NIH National Library of Medicine guidance on insulin syringes and injection technique. The U-100 standard this calculator assumes is the one used there: 100 units of fluid per millilitre, so 1 unit = 0.01 mL.

• Bacteriostatic Water for Injection labelling — DailyMed ↗

  Official FDA labelling for the diluent, including its 0.9% benzyl alcohol preservative and why that allows a multi-dose vial to be used over time.

Syringe gradations vary by brand and size: 0.3 mL and 0.5 mL barrels are usually marked in single units and 1 mL barrels every two. Half-unit 0.3 mL barrels are also sold — if that is what you have, switch on “½-unit marks” beside the syringe selector and every figure adjusts to it. Read the barrel in your hand before drawing; the setting records what you tell us, it is not something we can detect.