PurityPaulOR said:

Do it in two steps and it stops being confusing.

I am going to disagree with reconstituting low as a general rule. More diluent, more punctures, more in-use days at room temperature, and the stability trade-off is real. Precision is not the only variable being optimised.

TirzTom 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…

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.

kate.chem said:

I am going to disagree with reconstituting low as a general rule.

Reconstitution tip for anyone mixing dosing arithmetic from lyophilized powder: use bacteriostatic water, NOT sterile water. The benzyl alcohol in BAC water preserves multi-dose vials for up to 28 days.

Inject the water slowly down the side of the vial. NEVER shake — gentle swirling only until fully dissolved. Should be crystal clear with no particles.

A narrower follow-up, since the general answer is now clear:

How much material I am losing to dead space, and whether that explains why a 10mg vial gives me nine usable draws rather than ten?

Closing the loop on my own question.

Follow-up: it was dead space. Switching to a low-dead-space fixed-needle syringe gave me the tenth dose back.