SURMOUNT-5: Tirzepatide vs semaglutide head-to-head — November 2025

Dr.Martinez said:

Start from the measurement rather than the conclusion.

There is a second half to this that has not been said yet. Albumin binding above 99% is the whole reason weekly dosing works, and it is also why the trough matters more than the peak. People who dose late are not losing a peak, they are letting the trough fall, and the appetite effect tracks the trough.

One concrete data point for the thread. For anyone assembling their own picture: Tmax is one to three days, terminal half-life about 165 to 170 hours, steady state at four to five weeks, and subcutaneous bioavailability near 89%. Those four numbers explain most of the questions people ask about timing.

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

One thing that is still open after Dr.Martinez’s answer:

What the dose-response curve actually looks like above 1.7mg, because the trial means hide how few people account for the extra loss?

Dr.RaviCardio said:

For anyone assembling their own picture: Tmax is one to three days, terminal half-life about 165 to 170 hours, steady state at four to five weeks, and…

Filing a mild objection. Mild because I might be wrong; an objection because nobody has addressed the case that does not fit. The trial means are being read too generously in this thread. STEP populations were selected, supported, and titrated by protocol, and the real-world curves are consistently a few points worse. That difference is not noise, it is what happens when you remove the study infrastructure.

I would rather be corrected than agreed with, if it comes to it.

Dr.RaviCardio said:

For anyone assembling their own picture: Tmax is one to three days, terminal half-life about 165 to 170 hours, steady state at four to five weeks, and…

That holds for the injectable. The oral formulation has different absorption behaviour and the dose numbers are not interchangeable, which is worth saying out loud because people quote them as if they were.