Reconstituting a peptide means mixing the freeze-dried powder in the vial with bacteriostatic water so it can be injected. Mixing it isn't the hard part — once it's mixed, every single dose depends on a calculation you have to get right every time. That's why we built the Reconstitution Calculator.
In short: Enter your vial's mg (or mcg), the bacteriostatic water you added, and the dose you want to give, and the calculator returns the exact units to draw on your insulin syringe (U30, U50, or U100), with a syringe drawing and a print/save-to-PDF button. The dose itself comes from your protocol or your doctor — the tool just does the arithmetic.
How it works
The calculator asks for three inputs and works out everything else from there:
- 1Vial amount. The mg or mcg of peptide the vial contains (it arrives freeze-dried, as a powder).
- 2Bacteriostatic water added. How many milliliters of water you added to the vial.
- 3Desired dose and syringe type. The dose you want to give, and whether your insulin syringe is U30, U50, or U100 (the most common one).
With those three numbers, the calculator tells you exactly which unit mark on the syringe to draw up to, with a visual drawing so you don't have to translate numbers into syringe lines yourself. If the dose you asked for exceeds the capacity of the syringe you picked, it warns you instead of giving you an impossible-to-draw result — and there are two ways out: a bigger syringe, or more bacteriostatic water (which lowers concentration and raises the volume per dose).
The math behind it, in plain terms
You don't need to memorize the formula, but understanding it helps you trust the result. First, the vial's mg divided by the mL of water you added gives you the concentration (mg per mL). Then, your dose divided by that concentration, times 100, gives you the units to draw on a U100 syringe — because on a U100 insulin syringe, 100 units equal 1 mL. Switching syringe type (U30, U50) only changes the scale of the lines, not the underlying math.
Reconstituting the same vial with more or less water doesn't change the total amount of peptide you have — it changes how many units you need to draw to reach the same dose. More water = more diluted = more units per dose (but also more room to measure precisely on smaller syringes).
How to get the most out of it
- Always use the same amount of water for the same vial. If you reconstitute today with 2 mL and next time with 3 mL "because you didn't remember," the concentration changes and the units you used before no longer match the same dose.
- Confirm the syringe type before reading the result. Units on a U30 and a U50 look different on the syringe itself — picking the right type in the calculator is what makes the drawing match what you're actually holding.
- Save or print the result the first time you reconstitute a new vial. The print/PDF button exists exactly so you don't have to redo the math every week for the same vial.
- If you switch vials or concentration, recalculate from scratch. Don't reuse the previous vial's units — a new vial with a different amount of peptide or different water added changes the concentration, even if it's the same peptide.
If you also want to keep a history of every vial you reconstitute, with dose reminders and a log that doesn't depend on memory, PeptiBrain lets you save each calculation alongside your actual injections.
