Peptides/Weight and appetite
Tirzepatide
Also sold as Mounjaro, Zepbound
The strongest weight loss medicine currently approved. It works on two gut hormones instead of one, and trial results reached about 20%.
At a glance
What people use it for
- Losing a large amount of weight
- Managing type 2 diabetes
- Obstructive sleep apnoea in people with obesity
How it is taken
A once-weekly injection using a pre-filled pen, starting at a low dose and increasing every four weeks.
Evidence
Strong human evidence
Best known for
- About 20% of body weight lost over 72 weeks in SURMOUNT-1
- Beat semaglutide directly on both weight and blood sugar
- Approved for sleep apnoea as well as weight and diabetes
- Acts on two gut hormone receptors rather than one
Tirzepatide does what semaglutide does, and then a bit more. It mimics two gut hormones rather than one: GLP-1, which reduces appetite, and GIP, which appears to improve how the body handles fat and sugar. In head-to-head results it produces more weight loss than any other approved medicine.
It is sold as Mounjaro for type 2 diabetes and as Zepbound for weight management, which are the same molecule licensed for two purposes.
Why people are talking about it
The number. About 20% of body weight over 72 weeks is close to territory that used to be reserved for bariatric surgery, and it arrived only a couple of years after semaglutide had already reset expectations.
The sleep apnoea approval is the part most likely to be underrated. For anyone who has been sleeping badly for years, that is a bigger day-to-day change than the figure on the scale.
What people take it for
The same reasons as semaglutide, often after semaglutide either stopped working well enough or was never quite enough to begin with. Appetite drops, meals get smaller without much effort, and the mental noise around food fades.
It is also approved for type 2 diabetes, and more recently for sleep apnoea in people carrying significant excess weight.
Why two hormones rather than one
GLP-1 is the appetite signal. GIP is the other main incretin, released from the gut after eating, and its role in appetite and fat handling was considered unhelpful for years before the tirzepatide results forced a rethink.
In practice the drug pulls two levers on the same system rather than pulling one harder. Whether the extra weight loss comes specifically from the GIP arm or from the combination is still argued about in the literature, and nobody has isolated it in people.
What the evidence shows
In the SURMOUNT-1 trial, adults without diabetes lost about 20% of their body weight on the highest dose over 72 weeks. In SURPASS-2, it beat semaglutide directly on both blood sugar and weight. These are large randomised trials, not observational data.
The sleep apnoea result is a measured clinical outcome rather than a weight proxy. In the SURMOUNT-OSA trials, apnoea events per hour fell substantially, and for a proportion of participants the condition improved enough to change how it was managed.
What is still missing is a completed cardiovascular outcome trial of the kind semaglutide has. That work is running rather than finished, so on heart outcomes specifically the older drug currently has the better evidence.
The muscle question applies here at least as much as with semaglutide, because the total weight loss is larger. Protein intake and resistance training are the levers anyone has to influence that, and both are worth taking seriously from the start rather than later.
How it is taken
The licensed products are once-weekly pen injections, starting at a low dose and increasing at roughly four-week intervals. The schedule exists to manage the digestive side effects rather than to slow anyone down. Nausea, loose stools and reflux are common early and after each step up, and most people find they settle.
Dose, escalation and stopping belong to the prescriber.
How it compares
Against semaglutide
For weight loss and blood sugar, the direct comparison in SURPASS-2 favoured tirzepatide. For cardiovascular outcomes, semaglutide has the completed trial and tirzepatide does not, so the better answer depends on what is being asked.
Against surgery
The average results now overlap with some bariatric procedures. The two have not been compared head to head over the long term, and surgery has decades of durability data that the medicine does not yet have.
Common questions
Is it better than semaglutide?
On weight and blood sugar, the trial says yes. On heart outcomes, semaglutide has the finished evidence.
Do I have to stay on it?
Trials that withdrew it saw substantial regain. It behaves like a treatment for an ongoing condition rather than a course with an end date.
Why are there two brand names?
One licence covers type 2 diabetes and the other covers weight management. The molecule is the same, and the separation is regulatory rather than pharmacological.
How long until it works?
Appetite usually shifts in the first week or two. The weight curve in the trials kept going for well over a year before flattening.
Last reviewed .