Dr.BariatricHTX said:

Dead space is the answer to the missing dose.

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.

Dr.RenalNash 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…

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.

PeptideChemSF said:

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

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

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?

Reporting back.

My error was treating units as a mass. Once I wrote mg/ml on the vial in marker and worked in millilitres first, the two of us got the same answer.