In the Peptra app
Peptide reconstitution, done for you
Reconstitution is two divisions and a multiply: vial strength and the water you add give a concentration, and your amount gives the syringe volume. Peptra does that math for you — then saves the vial and counts down what's left. Here's exactly how it works, and where to get it.
Example · in the app
5 mg vial · 2 mL water · 250 mcg → 2500 mcg/mL · 0.1 mL · 20 doses per vial
The interactive tool lives in Peptra, where it saves straight to your vial inventory and tracks doses and days remaining — arithmetic on your numbers, never a recommendation.
How the maths works
Reconstitution is two divisions and one multiplication. Once you have seen it done, the calculator above is only saving you the arithmetic.
1. Work out the concentration
The vial holds a fixed amount of peptide. Adding bacteriostatic water does not change that amount — it only spreads it through a volume. Concentration is total amount divided by water volume.
5 mg = 5000 mcg ÷ 2 mL = 2500 mcg per mL
2. Work out the volume for your dose
Divide the dose you want by that concentration.
250 mcg ÷ 2500 mcg/mL = 0.1 mL
3. Convert millilitres to syringe units
Insulin syringes are marked in units, where 1 mL is 100 units. So multiply the volume by 100.
0.1 mL × 100 = 10 units
U-100 and U-50 read the same
This trips people up constantly. A U-100 syringe holds 1 mL across 100 unit marks. A U-50 holds 0.5 mL across 50 marks. Both work out to 100 units per millilitre, so the same volume draws to the same number on either barrel. The difference between them is how much they hold, not how they are graduated.
That is why the calculator above uses your syringe choice to warn you when a draw will not fit — never to change the number of units.
More water does not mean more peptide
Adding more bacteriostatic water makes the solution weaker, not your dose smaller. The same 250 mcg is still 250 mcg; it just arrives in a bigger, easier-to-measure volume. People often reconstitute with more water precisely so that small doses land on a readable part of the barrel.
The same 250 mcg dose, three dilutions
| Vial | Water | Concentration | Draw to |
|---|---|---|---|
| 5 mg | 1 mL | 5000 mcg/mL | 5 units |
| 5 mg | 2 mL | 2500 mcg/mL | 10 units |
| 5 mg | 3 mL | 1667 mcg/mL | 15 units |
Every row delivers exactly the same amount of peptide. The third is simply easier to measure accurately, because 15 marks are easier to hit than 5.
Why a draw under two units is a problem
On a standard barrel, the space between unit marks is small. A dose that works out to one or two units leaves very little room for error — a slight misread is a large percentage of the dose. If your draw lands there, reconstituting with more water moves the same dose onto a part of the scale you can actually read. The calculator flags this when it happens.
Peptra does this on your phone, and remembers it. Save the vial once and the app tracks the concentration, how many doses are left, and how many days that gives you at your schedule — then warns you before it runs out or expires. Get the app →