This one has a reasonably settled answer, so here it is. Concentration choice is a precision decision, not a preference. Reconstitute high and every dose is a tiny volume where one unit of syringe error is a large fraction of the dose. Reconstitute low and you get more graduations per dose, so the same hand tremor costs proportionally less. Against that, more diluent means more benzyl alcohol and a shorter comfortable in-use window.

PharmD_Rodriguez said:

Concentration choice is a precision decision, not a preference.

Agreed, and it is worth saying that rounding to the nearest whole unit is usually acceptable at maintenance doses and is not acceptable at the bottom of a ladder, where one unit can be a fifth of the intended dose.

Dr.NephBHM_UK said:

I reconstituted a 10mg vial with 2ml of bacteriostatic water and I want someone to check my unit arithmetic before I draw anything, because I keep…

This matches mine closely enough to be worth saying so. Dead space is the answer to the missing dose. A fixed-needle insulin syringe holds a few microlitres in the hub and needle after the plunger bottoms out, and on small draws that is a measurable percentage of every dose. Across ten draws it adds up to most of an eleventh, which is exactly the "nine draws from a ten-dose vial" complaint. Luer-lock syringes are worse; low-dead-space fixed-needle designs are better.

From the other side of the consultation, briefly.

dosing arithmetic — critical reminder about tirzepatide dose equivalence across formulations:

Mounjaro KwikPen and compounded tirzepatide are the same molecule but:

• KwikPen is ready to inject, no mixing needed
• Compounded requires reconstitution and proper syringe technique
• Verify your compounded concentration before each injection
• Never assume 1 vial = 1 dose without checking the math