reconstitution is the most under-discussed thing on this board
Thinking out loud about this: reconstitution is the most under-discussed thing on this board.
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.
The arithmetic in full: concentration is mass over volume, so 15mg into 1mL gives 15mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1.5mg is 1.5 divided by 15 millilitres, which is 10 units.
Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.
If somebody has the same thing measured a different way, post it next to mine and we will see whether they agree.
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.
do the arithmetic before you reconstitute, not while holding a syringe
The whole calculation, once, with real numbers.
You have a 5mg vial. You add 3mL of bacteriostatic water. Concentration is mass over volume: 1.67mg/mL. A U-100 insulin syringe is graduated at 100 units per millilitre, so one unit is 0.01mL.
To draw 1mg you need 1 divided by 1.67 millilitres, which is 60 units on the barrel. Write "1.67mg/mL" on the vial in marker before you put it away, and you never have to do this again for that vial.
The whole calculation, once, with real numbers.
ledger_mod has the units point exactly right. They are a volume on the barrel and nothing else.
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.
Are you accounting for the powder volume, or is that where the confusion is?