The figures, for anyone assembling their own picture. Practical numbers: half-life about 5 days, steady state 3 to 4 weeks, ladder 2.5 / 5 / 7.5 / 10 / 12.5 / 15mg, and the maintenance doses with published data behind them are 5, 10 and 15mg.

Worth separating that from tirzepatide, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

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?

Dr.AddMedPHL said:

Practical numbers: half-life about 5 days, steady state 3 to 4 weeks, ladder 2.5 / 5 / 7.5 / 10 / 12.5 / 15mg, and the maintenance doses with…

Coming at Dr.AddMedPHL’s question from a different direction. Steady state is faster than people expect: half-life about five days, so you are at plateau in roughly three to four weeks rather than five. That matters when you are deciding whether a dose step has finished expressing itself.

Worth separating that from tirzepatide, which this thread keeps folding into the same question. They behave differently and the advice does not transfer.

Reporting back.

Resolved. I wrote mg, ml and mg/ml on the vial in marker and did the division in that order, and the two of us now get the same number every time.

PharmHunterJen said:

Steady state is faster than people expect: half-life about five days, so you are at plateau in roughly three to four weeks rather than five.

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.

Happy to go further on any of that.