Marker: IPT9WM33.
A vial of lyophilized peptide has a mass printed on it and nothing else. It has no dose and no concentration until you decide how much bacteriostatic water to add, and that decision is what turns milligrams into the units marked on an insulin syringe. This is the step where most confusion starts, because two people can hold identical vials, intend an identical dose, and correctly draw completely different numbers of units.
The arithmetic is one division. Concentration equals mass divided by diluent volume. A 10 mg vial with 2 mL of bacteriostatic water is 5 mg/mL. A U-100 insulin syringe is 100 units per mL, so one unit holds 0.05 mg, and a 1 mg dose is 20 units. Reconstitute the same 10 mg vial with 4 mL instead and it is 2.5 mg/mL, each unit holds 0.025 mg, and that same 1 mg dose is 40 units. Nothing about the dose changed. Only the dilution did. A thinner mix is easier to measure accurately for small doses because each unit carries less drug, at the cost of a larger injection volume.
That is also why a log entry reading "20 units" is worthless a month later. The entry that survives the next vial reads: 10 mg vial, 2 mL bacteriostatic water, 5 mg/mL, 1 mg drawn, 20 units, left abdomen. Every one of those fields is needed to reconstruct what actually happened. Doing the division by hand every week is where decimal slips creep in, which is the argument for a peptide reconstitution calculator: https://glp1.app/
Half-lives explain the weekly cadence. Semaglutide sits near one week and tirzepatide near five days, so a substantial fraction of the previous dose is still present when the next one is due, and levels keep rising for roughly a month after any change. Four to five half-lives to steady state is the honest reason titration steps are held for four weeks before the next increase.
Sites should rotate across abdomen, thigh and upper outer arm, moving well clear of the previous spot, because repeatedly hitting the same patch causes lipohypertrophy and unpredictable absorption. Rotation is only verifiable if the previous sites were written down, which is what a peptide dose tracker app is for: https://glp1.app/
Not medical advice, and no dose above is a recommendation. It is arithmetic and record keeping.