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Reconstitution · Syringe units

Peptide Reconstitution Calculator

This tool only does arithmetic with the numbers you enter. It does not suggest a dose, a product or a schedule. Many peptides are prescription-only or not approved for human use. Follow the label and the instructions from your prescriber or pharmacist, and check every result yourself.

The amount printed on the vial, in milligrams. For 5000 mcg enter 5.

The volume of liquid you add to the vial.

Enter the dose you were told to use. Check whether it is in mcg or mg, because mixing them up gives a result 1000 times too large or too small.

U-100 insulin syringes have 100 units per mL. Read the scale printed on your syringe.

Draw to
10.0units
Volume to draw
0.1 mL
Concentration
2.5 mg/mL
Peptide in one syringe unit
25 mcg
Whole doses in the vial
20
How it was worked out
  1. Concentration = 5 mg / 2 mL = 2.5 mg per mL.
  2. Dose = 250 (entered), which is 0.25 mg.
  3. Volume to draw = 0.25 mg / 2.5 mg per mL = 0.1 mL.
  4. Syringe units = 0.1 mL x 100 units per mL = 10.0 units.

Check the result: the volume and units above must match your syringe markings, and the numbers must match the vial label. If anything looks very different from what you expected, stop and ask your pharmacist or prescriber.

Arithmetic helper, not medical advice. Results are only as correct as the numbers you enter.

Concentration, volume to draw and syringe units from vial size, water added and your dose. Arithmetic only. · U-100 syringe scale checked against an FDA drug label

Reviewed by Abdul Rafay (arithmetic and unit scale source-checked, November 2026; not a medical review) · Published November 2026 · Unit scale checked November 2026

This calculator is an arithmetic helper, not medical advice. It does not suggest a dose, a product or a schedule. Many peptides are prescription-only or not approved for human use. Follow the label and your prescriber's or pharmacist's instructions. A wrong input, such as the wrong unit or a misplaced decimal point, gives a wrong and possibly dangerous result, so check every number against the vial label and your syringe.

Worked example

A 5 mg vial with 2 mL of water added, and a dose of 250 mcg drawn with a U-100 syringe:

Example: 5 mg vial, 2 mL water, 250 mcg dose, U-100 syringe
StepResult
Concentration: 5 mg / 2 mL2.5 mg per mL
Dose in mg: 250 mcg / 10000.25 mg
Volume: 0.25 mg / 2.5 mg per mL0.1 mL
Units: 0.1 mL x 100 units per mL10 units
Doses in the vial: 5 mg / 0.25 mg20

How the calculator works

The formulas

  1. 01

    Concentration

    Concentration is the amount of peptide per mL of liquid: vial amount in mg divided by the water added in mL. Adding more water makes the mixture weaker per mL.

  2. 02

    Volume to draw

    Volume is the dose in mg divided by the concentration in mg per mL. A dose in mcg is divided by 1000 first to get mg.

  3. 03

    Syringe units

    Units are the volume in mL times the units per mL on your syringe scale. A U-100 insulin syringe has 100 units per mL, so 0.1 mL is 10 units (the U-100 scale is stated on FDA insulin labels).

  4. 04

    Doses in the vial

    The vial amount divided by the dose, rounded down to a whole number. It ignores any loss when drawing.

  5. 05

    Why the checks appear

    A warning shows when the draw is more than the syringe can hold, when it is under 1 unit and hard to measure, or when the dose is larger than the whole vial. These usually mean a number was entered in the wrong unit.

  6. 06

    What the tool does not do

    It does not recommend doses, products or schedules, does not check whether a substance is safe or legal, and does not know how a particular vial should be prepared. Use the instructions that come with it.

Common questions

Questions about reconstitution math

How do I convert a dose in mcg to syringe units?

Divide the dose by 1000 to get mg, divide that by the concentration in mg per mL to get mL, then multiply by the units per mL on your syringe. The result shows every step.

How much water should I add to the vial?

This tool does not tell you. Follow the instructions that came with your vial or ask your pharmacist or prescriber. You enter the amount you used, and the calculator shows what that means for each dose.

How many units is 0.1 mL?

On a U-100 syringe, 0.1 mL is 10 units, because the scale has 100 units per mL. On a U-40 syringe the same 0.1 mL is 4 units, so always read the scale printed on your syringe.

Why does adding more water not change the amount of peptide?

The total peptide in the vial stays the same. More water lowers the concentration, so a given dose takes a larger volume to draw, which is easier to measure.

Does this work for any substance in a vial?

The arithmetic works for any powder dissolved in a liquid, but the tool knows nothing about the substance. It cannot tell you whether a dose is safe or appropriate.

Is my data saved?

Nothing is sent or stored on a server. The numbers stay in your browser and in the page address, so you can bookmark or share the filled-in form.