Short answer first, then the reasoning. 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.

kate.chem 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.

True, though the ladder is longer and that is not a neutral detail — six dose steps means six opportunities to stall on the way up, and plenty of people never reach the dose the headline number came from.

If somebody has the primary source to hand I would rather cite it than paraphrase it.

maria_elpaso said:

I moved from semaglutide to tirzepatide after a long stall and the first eight weeks looked like starting over — which I gather is the usual pattern…

Same position here, arrived at the long way round. SURMOUNT-1 landed around 20.9% mean weight loss at 15mg over 72 weeks, against roughly 15% for semaglutide 2.4mg in STEP 1. Different trials, different populations, so the comparison is indicative rather than decisive — but SURPASS-2 was a genuine head-to-head and it pointed the same way.

From the other side of the consultation, briefly.

Dose-response modeling for tirzepatide: Emax model fitting to the STEP/SURMOUNT dose-finding data shows:

Semaglutide: ED50 ≈ 0.6mg, Emax ≈ -18%, Hill coefficient ≈ 1.3
Tirzepatide: ED50 ≈ 6mg, Emax ≈ -25%, Hill coefficient ≈ 1.5

Clinical implication: most patients achieve >80% of maximal response by the mid-range dose (1.7mg sema, 10mg tirz). Going to the maximum dose provides diminishing returns — possibly not worth the additional side effect burden for some patients. Individualize dosing based on response vs tolerability.