bacteriostatic water is the most under-discussed thing on this board
bacteriostatic water is the most under-discussed thing on this board. Not a hot take, just something I have not seen said plainly here. Wrote the date on the vial as well as the concentration after losing track of which one was opened first. Shook the first vial because nobody told me not to. It was fine, but I have…
swirl, never shake
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
write the concentration on the vial in marker, that is the whole post
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
I would not round that figure. At 5mg/mL a rounding error of two units is a real fraction of the intended amount.
The whole calculation, once, with real numbers.
You have a 20mg vial. You add 3mL of bacteriostatic water. Concentration is mass over volume: 6.67mg/mL. A U-100 insulin syringe is graduated at 100 units per millilitre, so one unit is 0.01mL.
To draw 5mg you need 5 divided by 6.67 millilitres, which is 75 units on the barrel. Write "6.67mg/mL" on the vial in marker before you put it away, and you never have to do this again for that vial.