mg/mL is the most under-discussed thing on this board
mg/mL is the most under-discussed thing on this board. Not a hot take, just something I have not seen said plainly here. Adding more water does not change how much peptide is in the vial. It changes the concentration, which changes the volume you draw for the same amount. That is the entire relationship. Why "more…
The whole calculation, once, with real numbers.
You have a 10mg vial. You add 3mL of bacteriostatic water. Concentration is mass over volume: 3.33mg/mL. A U-100 insulin syringe is graduated at 100 units per millilitre, so one unit is 0.01mL.
To draw 2mg you need 2 divided by 3.33 millilitres, which is 60 units on the barrel. Write "3.33mg/mL" on the vial in marker before you put it away, and you never have to do this again for that vial.
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.
Yes. Writing 10mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.
Bacteriostatic water contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable. Plain sterile water has no preservative.
This. Showing the working is the fastest way for somebody else to spot the mistake.
Left up and flaired Explainer — the numbers in this one check out.