Semaglutide vs tirzepatide

The head-to-head, in full

Most comparisons in this category are assembled from separate trials that were never run against each other — different participants, different durations, different definitions. This one does not have to be. SURMOUNT-5 put both molecules in the same trial.

Two things about that trial deserve stating rather than burying. It was open-label — participants and investigators knew which drug was being given, which can influence reported outcomes. And it was funded by Eli Lilly, which makes tirzepatide. Neither fact makes the result wrong. Both are ordinary in drug trials, and both are the sort of thing a reader is entitled to weigh for themselves.

A six-point difference in a group average is a real difference. It is not a promise about what either drug will do for one person, and the trial was not designed to make one.

On the heart, there is no comparison — and the reason is the comparator

This is where most pages on this subject go wrong. Both molecules have a large cardiovascular outcomes trial, and it is tempting to line the two results up. They do not line up, because the trials asked different questions of different people.

Read the first row and the rest follows. Beating a placebo and matching a drug that already works are different achievements. A drug that matches dulaglutide may well be as good for the heart as one that beats placebo — or better, or not — but that trial was not run, and the populations were not the same either: SELECT enrolled people without diabetes, SURPASS-CVOT people with it.

What can be said plainly: semaglutide carries an FDA indication for reducing cardiovascular events in people with cardiovascular disease and overweight or obesity. Tirzepatide does not carry that indication for this use. That is a regulatory fact rather than a verdict on the molecules, and if cardiovascular risk is the reason you are considering treatment, it is the fact most worth raising with your prescriber.

How they actually differ

• One receptor versus two. Semaglutide activates the GLP-1 receptor. Tirzepatide activates GLP-1 and GIP, which is why it is called a dual agonist — see how these medications work.
• Formats. Both are weekly injections. Only semaglutide is also sold as a daily tablet — see the format comparison.
• Brand names. Semaglutide is sold as Ozempic, Wegovy and Rybelsus; tirzepatide as Mounjaro and Zepbound. Which brand you are offered depends on the approved use, not on the molecule — see class, molecule and brand.
• What they share. The same boxed warning about thyroid C-cell tumours observed in rodents, and the same contraindications. Neither is the safer option on that count.

The format difference in that second bullet is also the price difference, and it is larger than most comparisons of these two molecules admit. Because semaglutide is sold as a tablet and tirzepatide is not, the two have different price floors set by different things — which is why the cheapest semaglutide is not an injection while tirzepatide is priced from the pen down. Each of those pages lists every provider in our directory whose own wording names that molecule, with membership fees added to the medication.

Side effects: what can and cannot be compared

In the head-to-head, the most common adverse events in both groups were gastrointestinal, most were mild to moderate, and they occurred mainly during dose escalation. That is a genuine same-trial observation.

The labelled rates below are not a head-to-head. They come from each product’s own trials against placebo, with different participants and definitions, so treat the columns as two separate facts rather than a race:

What is common to both, and what is serious, is on the side-effects guide.

Questions people ask

Is tirzepatide better than semaglutide?

For weight loss, the only head-to-head trial says yes. SURMOUNT-5 randomised 751 adults with obesity and no diabetes to one or the other for 72 weeks: tirzepatide produced a 20.2% mean reduction in body weight against 13.7% for semaglutide. That is a real result from a real comparison rather than an inference across separate trials. It is not the whole picture, because weight is not the only thing either drug is prescribed for, and the trial was open-label and funded by the company that makes tirzepatide.

Which one is better for your heart?

Nobody knows, and the trials cannot tell you. Semaglutide was tested against placebo in SELECT and cut major adverse cardiovascular events by 20%, which earned it an FDA indication for cardiovascular risk reduction. Tirzepatide was tested in SURPASS-CVOT against dulaglutide — a drug already shown to reduce cardiovascular events — in people with type 2 diabetes, and was found noninferior but not superior. Beating a placebo and matching an active drug are different achievements in different populations. No cardiovascular trial has randomised anyone between these two molecules.

What is the actual difference between them?

Semaglutide acts at one receptor, GLP-1. Tirzepatide acts at two, GLP-1 and GIP, which is why it is called a dual agonist. Both are weekly injections; semaglutide is also available as a daily tablet. They carry the same boxed warning about thyroid C-cell tumours seen in rodents, and the same contraindications.

Which has worse side effects?

In their separate trials the most common effects were gastrointestinal for both. In the head-to-head, the most common adverse events in both groups were gastrointestinal and most were mild to moderate, occurring mainly during dose escalation. Our side-effects page gives the labelled rates for each product side by side, but those come from different trials and are not a head-to-head comparison of tolerability.

Can you switch from one to the other?

That is a prescriber decision, not a self-directed one. People do switch, for tolerability, cost, or supply reasons, and the dosing does not transfer across — the two molecules use different dose scales and both need titrating from a low starting dose. Ask the person who wrote your prescription.

This page is general education, not medical advice. Talk to your own healthcare provider about your situation before starting, stopping, or changing any medication.