Math is hard - help me with reconstitution please

Taking the question as asked, rather than the general version of it. 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.

Happy to go further on any of that.

PeptideChemSF 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.

WendyG_ATL 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.

Adding the clinical framing, because it changes how the question reads.

Ongoing cost tracking for dosing arithmetic — transparency for the community:

Monthly medication cost: $143
Supplies (syringes, BAC water, alcohol swabs): ~$11/month
Janoshik testing: ~$13/month (amortized quarterly)
Lab work: ~$43/month (amortized quarterly)
Total: ~$193/month

Compare to brand Wegovy at $1383/month without insurance. Compounded is roughly 88% cheaper for what I have found to be clinically equivalent medication.