Bacteriostatic water sourcing guide — my results so far

Short answer first, then the reasoning. 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.

sarah.morrison 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.

MASHdoc_SA 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…

Can confirm the pattern MASHdoc_SA describes. 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.

Sharing my dosing arithmetic titration experience with compounded semaglutide — I have been tracking injection volumes meticulously:

Using 5mg/2mL concentration with 1cc insulin syringes:

• Month 1: 10 units (0.25mg) — mild appetite reduction
• Month 2: 20 units (0.5mg) — significant appetite suppression
• Month 3: 30 units (0.75mg) — custom intermediate dose
• Month 4: 40 units (1.0mg) — optimal for me, staying here

The beauty of compounded vials is you can do custom intermediate doses. My provider was great about tailoring to my response.