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.

Ask again with the specifics and you will get a better answer than this one.

Dr.LipidDallas said:

Concentration choice is a precision decision, not a preference.

That is correct as far as it goes, and here is where it stops going. The arithmetic is right and one caveat matters: a U-40 syringe changes the markings, not the volumes. If someone hands you U-40 and you read it as U-100 you will be 2.5 times out, and that error has a direction — it is always an overdose.

Correct me if the detail matters more than I have assumed.

denise_HTX said:

Two of us with identical vials and identical diluent arrived at different unit counts, which means one of us has a conceptual error rather than a…

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.

Clinical perspective, offered as context rather than as advice.

Just received my dosing arithmetic order — packaging review:

• Outer box: plain brown, no medication identifiers (discreet) ✅
• Inner insulation: Styrofoam with 2 gel ice packs ✅
• Temperature: vials were cold to touch on arrival ✅
• Labeling: lot number, BUD, compound name, concentration ✅
• Included: COA, reconstitution instructions, dosing card ✅

This is what professional compounding pharmacy shipping looks like. If your order arrives without these basics, reconsider your vendor.