This one has a reasonably settled answer, so here it is. 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.

Dr.SurgeonPGH 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.

Agreed on the mechanism, with the caveat that the head-to-head used semaglutide 1mg, not 2.4mg. It is still the best direct evidence available, but it is not the comparison most people think they are citing.

DoseLogDan said:

Fourteen months on tirzepatide, currently 10mg, and I stopped escalating because 10mg is doing the job and 15mg made me feel flat rather than full.

This matches mine closely enough to be worth saying so. 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.

Adding the clinical framing, because it changes how the question reads.

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.