Peptide Reconstitution & Dose Calculator

What reconstitution actually means

Peptides ship as a dry powder. That powder has been freeze-dried — the word you will see is lyophilised — because peptides are far more stable dry than wet. Reconstitution is simply the step where you add liquid and turn that powder back into something you can measure.

The liquid is normally bacteriostatic water: sterile water with a small amount of benzyl alcohol in it, which stops bacteria growing so the vial survives being punctured more than once.

That is why there is no universal chart that says “draw to 10 units.” The number of units you draw depends on a choice you made a few minutes earlier. Get that relationship straight and the rest of this is just arithmetic.

The math, done once by hand

You do not need to do this yourself — that is what the tool is for. But seeing it once means you can sanity-check any answer, and catching a wrong answer matters more than getting a fast one.

There are only two facts to hold on to:

• 1 mg = 1,000 mcg. Vials are labelled in milligrams. Doses are usually discussed in micrograms. Almost every serious dosing error in this space lives in that gap.
• On a U-100 syringe, 100 units = 1 mL. So 1 unit is 0.01 mL. This is true of the 1 mL, 0.5 mL and 0.3 mL syringes alike — they just show a different number of lines.

Now change one thing. Same vial, same dose, but you added 1 mL of water instead of two. The concentration doubles to 10,000 mcg/mL, and the same 250 mcg dose becomes 2.5 units — half a line, on the most crowded part of the barrel.

Add 5 mL instead and it becomes 12.5 units. Still half a line, but on a much easier stretch of the syringe to read.

How much water should I add?

This is the most-asked question in reconstitution, and the honest answer surprises people: within reason, it is your choice, and there is no single right number.

The water does not change how much peptide you have. A 10 mg vial holds 10 mg whether you add 1 mL or 5 mL, and it will give you exactly the same number of doses either way. What the water changes is how easy your dose is to measure accurately.

Aim for a readable fill line

The practical target is a dose that lands somewhere around 5 to 30 units. Down at 2 or 3 units, a small wobble in the plunger is a large percentage error. Up near the top of the barrel you may not be able to fit the dose in one draw. In the middle, the lines are far enough apart to hit reliably.

Land on a whole line if you can

Whole numbers beat halves. In the worked example above, 2 mL of water put the dose on exactly 5 units. If a small change in your water volume moves you from 7.5 units to 8, take it — you will be drawing that line repeatedly, sometimes early in the morning, sometimes in poor light.

Respect the vial and the clock

Do not add more liquid than the vial comfortably holds. And remember that once a peptide is in solution its stable life is measured in weeks, not months — so there is no advantage in diluting a vial so far that you cannot finish it in time.

Six mistakes worth knowing about

• Confusing mg with mcg. One milligram is a thousand micrograms. This single slip is the source of most thousand-fold errors, and it is why the calculator asks for the vial in mg and the dose in mcg — the units are kept apart on purpose.
• Treating “units” as a dose. Units measure volume, not peptide. “I take 10 units” means nothing to anyone else, because their vial is a different strength to yours.
• Assuming the label gives you the concentration. It gives you the quantity. The concentration is created by you, when you choose the water.
• Shaking the vial. Swirl or roll. Foam means denatured peptide, and no amount of waiting fixes it.
• Not recalculating after a change. New vial size, new water volume, new syringe — any of these changes your fill line. Run the numbers again rather than reusing last month’s.
• Reusing needles. A needle is blunted by its first pass through a rubber stopper, and a blunt needle does more tissue damage than a sharp one.