Semaglutide vs tirzepatide: how to actually choose

The mechanical difference

Semaglutide is a GLP-1 receptor agonist. It mimics a hormone your gut already produces, slowing gastric emptying, increasing satiety signalling and stimulating glucose-dependent insulin secretion. The appetite effect, not the glycemic one, is what drives weight change.

Tirzepatide agonises two receptors — GIP as well as GLP-1. The accepted explanation for its efficacy advantage is that dual action, though how much the GIP component contributes is still genuinely debated among researchers.

Both are weekly injections. Both carry the same class boxed warning regarding thyroid C-cell tumours observed in rodents, and both share a broadly similar gastrointestinal side-effect profile concentrated during dose escalation.

What the trials show

In registrational trials, semaglutide produced average body-weight reduction in the mid-teens as a percentage at roughly 68 weeks. Tirzepatide produced roughly a fifth of starting body weight at about 72 weeks at higher doses — the largest figures recorded in this class.

Those are averages among people who stayed in the trials. Real-world results run materially lower, and the reason is almost entirely discontinuation rather than non-response. If you stop at month four, the trial average tells you nothing about your outcome.

The practical implication: the difference between these two molecules matters far less than whether you stay on either one. Choose the one you can tolerate and afford for a year, not the one with the better headline number.

The titration difference nobody mentions

Tirzepatide's ladder to its highest maintenance dose runs longer than semaglutide's. Both escalate roughly every four weeks, but tirzepatide has more rungs.

That has a direct financial consequence. You spend more months on drug — paying full price — before reaching the dose where the effect plateaus. If you are self-paying, model the whole ladder rather than the first month's promotional rate.

It also has a clinical one. A longer escalation means a longer window in the period where side effects concentrate, which is where most people who quit, quit.

Cost, as actually published

Among providers we verified, compounded pricing for the two molecules is close. Mochi publishes compounded semaglutide at $60 and compounded tirzepatide at $90. Lemonaid publishes both at $299/month standard, dropping with multi-month commitments.

Branded is where the gap widens and gets strange. Mochi publishes Wegovy and Zepbound both at $299 but Mounjaro at $499 and Ozempic at $199 — the same molecules at very different prices depending on which brand and indication you are buying.

Novo Nordisk's own pharmacy publishes Wegovy self-pay from $149/month for tablets up to $399/month for the 7.2 mg injection. That is the reference price for branded semaglutide; treat any quote well above it as carrying somebody's margin.

How to decide

If you are self-paying and price-sensitive: the compounded versions of both are close enough that tolerability should decide, not cost.

If you have insurance: whichever your plan covers wins, almost regardless of the trial data. A covered semaglutide beats an uncovered tirzepatide by a wide margin in every real budget.

If you have tried one and it did not work: that is a genuine clinical reason to try the other, and worth discussing with a prescriber rather than switching providers on your own.

If you are older or have lower baseline muscle: the larger reductions tirzepatide produces mean larger absolute lean-mass loss. Protein intake and resistance training matter more, not less, at higher efficacy.