[Math] 10mg vial + 2mL bac water, i want 2.5mg, how many units
10mg vial + 2mL bac water, i want 2.5mg, how many units, and I am aware this is a minority view on this board.
Hard numbers: 10mg, 2mL and 2.5mg. Anything softer than that is flagged as an impression.
Why "more water" keeps confusing people, including me for a month.
The vial contains a fixed amount of peptide. Water changes nothing about that amount. What it changes is concentration, and concentration is the divisor between the dose you want and the volume you draw.
So doubling the water halves the concentration and doubles the units for the same dose. Nothing is diluted in any sense that matters; you are simply reading a bigger number off the same barrel. Pick the water volume that puts your usual dose on a whole number of units and life gets easier.
The failure modes I have actually seen posted here, in order of frequency.
One: reconstituting at a different volume than intended and not writing it down, so the next draw is based on a remembered concentration. Two: treating units as a dose rather than a volume, which breaks the moment the concentration changes. Three: assuming a syringe is U-100 when it is not.
All three are solved by the same two habits — do the arithmetic before the water goes in, and write the result on the glass. Neither costs anything and between them they cover almost every question this board gets.
That is everything I have. The rest is opinion and I have tried to keep it out.
best — the order this archive was captured in
Aim the stream down the wall of the vial rather than into the cake. Reconstitution is a solubility problem, not a mixing problem, and mechanical shear does nothing helpful.
What concentration did you actually reconstitute at, rather than what did you intend to?
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
Show the arithmetic — where did the unit figure come from?
Small fix — a U-100 syringe is 100 units per mL. If yours is marked differently it is not U-100 and the whole calculation changes.
Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.
do the arithmetic before you reconstitute, not while holding a syringe
Same. I got this wrong once, caught it because the units looked absurd, and have written on every vial since.
The arithmetic in full: concentration is mass over volume, so 15mg into 3mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 0.25mg is 0.25 divided by 5 millilitres, which is 5 units.
the powder cake sits at the bottom, the volume you add is the volume that counts
Careful — that arithmetic is wrong. 10mg in 3mL is 3.33mg/mL, so 2.5mg draws to 75 units, not what you wrote.