Second pass at: Choosing a concentration on purpose rather than by accident

Arithmetic step by step: a 5 mg vial with 2 mL of diluent gives (5 mg) / (2 mL) = 2.5 mg/mL. On a U-100 syringe at that concentration, 100 units = 1 mL = 2.5 mg, so each unit = 0.025 mg. A 0.25 mg dose = 0.25 / 0.025 = 10 units. Different concentration: different arithmetic, same principle.

Written quickly, so the reasoning may be tighter than the wording.

Over-dilution: if your target dose is 0.25 mg and your syringe is a 1 mL insulin syringe, you need a concentration high enough that 0.25 mg fits on the scale. A 0.25 mg/mL solution requires drawing the entire 1 mL syringe — not readable. A 5 mg/mL solution requires drawing 50 μL — also not practical on an insulin syringe.

I would want the raw data before agreeing with my own summary of it.

Picking up post #18: that is the part I would want checked first.

Write the reconstitution date and the concentration on the vial. Not on a note, on the vial. Every account here of a dosing error involving the wrong concentration involves a vial with nothing written on it.

On Choosing a concentration the community has more anecdote than the confidence in this thread implies, and I include my own contribution in that.

Right, and stated more narrowly than I would have dared to state it.

Following this. I have the same question and no better information than the first post.

That reframing is the whole thing. The facts I already had.

Arithmetic step by step: a 5 mg vial with 2 mL of diluent gives (5 mg) / (2 mL) = 2.5 mg/mL. On a U-100 syringe at that concentration, 100 units = 1 mL = 2.5 mg, so each unit = 0.025 mg. A 0.25 mg dose = 0.25 / 0.025 = 10 units. Different concentration: different arithmetic, same principle.

Adding it in case it saves somebody the afternoon it cost me.