Reconstitution calculator
A lyophilised vial is a mass of powder with no volume. Reconstituting it creates a solution, and every figure that follows — what concentration you have, how much to withdraw, where that lands on a syringe barrel, how many draws the vial holds — comes from two numbers you choose: the mass in the vial and the volume of diluent you add.
For research calculation purposes only
The four figures, and where each comes from
Concentration (mg/mL)
vial mass ÷ diluent volumeThe only figure that depends on nothing but your two inputs. A 10 mg vial with 2 mL of diluent gives 5 mg/mL. This number drives all three below it.
Volume to withdraw (mL)
dose ÷ concentrationTo withdraw 0.5 mg from a 5 mg/mL solution you need 0.1 mL, because 0.5 ÷ 5 = 0.1. Note that this is a volume of solution, not a mass of compound.
U-100 units
volume in mL × 100Insulin syringes are graduated in units, not millilitres, and on the U-100 scale 100 units is exactly 1 mL. So 0.1 mL reads as 10 units. This is a unit conversion and nothing more.
Draws per vial
vial mass ÷ dose, rounded downA 10 mg vial at 0.5 mg per draw holds 20 draws. Always rounded down: a partial draw at the end of a vial is not a draw.
Diluent volume changes the reading, not the amount
This is the part that most often causes confusion. Adding more bacteriostatic water does not dilute what you withdraw, provided you recompute the volume. The same 10 mg vial, targeting 0.5 mg per draw:
| Diluent | Concentration | Withdraw | Reads as | Contains |
|---|---|---|---|---|
| 1 mL | 10 mg/mL | 0.05 mL | 5 units | 0.5 mg |
| 2 mL | 5 mg/mL | 0.1 mL | 10 units | 0.5 mg |
| 3 mL | 3.333 mg/mL | 0.15 mL | 15 units | 0.5 mg |
The final column does not move. What changes is how easy the measurement is to read: 5 units on a barrel is a much finer judgement than 15 units, so a larger diluent volume buys precision at the cost of more solution to store. That trade is the whole reason the choice exists.
Handling the vial
- Direct the diluent slowly down the inner wall of the vial rather than onto the powder directly.
- Swirl gently; never shake or vortex. Agitation denatures peptides. Dissolution can take several minutes and that is normal.
- Bacteriostatic water contains 0.9% benzyl alcohol as a preservative, which is what permits repeated entry to the vial. Plain sterile water has no preservative and is single-entry.
- Store reconstituted solution at 2 to 8 °C and protect it from light. Lyophilised powder is best kept frozen before reconstitution.
- GHK-Cu produces a deep blue solution. That is the copper(II) complex, not contamination.
Common questions
How much bacteriostatic water should be added to a vial?
There is no single correct volume. The diluent volume sets the concentration, and concentration only changes how large the withdrawn volume is — not how much compound it contains. More diluent gives a larger, easier-to-read volume on the barrel; less diluent gives a smaller one. Most work uses between 1 mL and 3 mL per vial, chosen so the intended draw lands in a readable part of the syringe scale.
What does mg/mL mean on a reconstituted vial?
It is the concentration: the mass of compound dissolved in each millilitre of solution. A 10 mg vial reconstituted with 2 mL of diluent yields 5 mg/mL, because 10 divided by 2 is 5. Every other figure on this page derives from that one number.
What is a U-100 unit?
U-100 is the scale printed on standard insulin syringes, where 100 units equals 1 millilitre. So 10 units is 0.1 mL and 50 units is 0.5 mL. The unit mark is a volume, not a mass — the same 10 units contains a different amount of compound at every different concentration.
Why does the calculator show whole draws only?
A vial that yields 20.8 draws yields 20 usable ones. Rounding up would promise a draw the vial cannot fill, so the figure is always rounded down.
Does adding more diluent reduce the amount of compound withdrawn?
No. Diluent volume changes the concentration and therefore the volume you withdraw, but not the mass contained in it. Reconstituting 10 mg in 1 mL and withdrawing 0.05 mL, or in 2 mL and withdrawing 0.1 mL, both carry 0.5 mg of compound.
How should a reconstituted vial be stored?
Lyophilised powder is stable at room temperature in transit and is best kept frozen for long-term storage. Once reconstituted, vials are refrigerated at 2 to 8 degrees Celsius and protected from light. Bacteriostatic water contains 0.9 percent benzyl alcohol, which is what allows repeat entry to the vial; sterile water without a preservative does not.
Reconstitution supplies
Bacteriostatic water, graduated syringes, alcohol prep pads and sterile empty vials for aliquoting are all stocked alongside the research catalogue.
All products sold on this website are intended for research and identification purposes only. These products are not intended for human dosing, injection, or ingestion. This page describes laboratory dilution arithmetic and vial handling only. It does not provide dosing guidance, schedules, or administration instructions of any kind.