the actual arithmetic for splitting a weekly mg total into two draws, worked example
Getting DMs asking to show the math instead of just saying "split it evenly" so here's a full worked example using round numbers. Say a vial is labelled 10mg and reconstituted with 2mL of bacteriostatic water. Concentration = 10mg ÷ 2mL = 5mg/mL. On a standard U-100 insulin syringe, 1mL = 100 units, so 5mg/mL means…
this is the cleanest worked version of this I've seen posted, and the closing point is the actual root cause of nearly every dosing math error in this community — reusing an old units number after changing either the vial strength or the reconstitution volume.
yeah I see that exact error pattern constantly, someone reconstitutes differently "because they ran low on bac water" and just keeps using the old unit count
and dead space compounds it, that 2-5 unit loss per draw becomes a bigger relative error once you're doing two smaller draws instead of one bigger one
which is an argument for reconstituting with a slightly higher concentration if you're going to split, fewer total units drawn means dead space eats a smaller fraction
good addition, higher concentration + splitting does pair better than low concentration + splitting for exactly that reason