Retatrutide is a once-weekly injection being developed for weight loss and type 2 diabetes. It builds on the hormone-based approach behind Ozempic and Mounjaro, with three targets instead of one or two. The interest comes from substantial weight loss in trials and the possibility of another treatment option for people with obesity.
It’s still experimental. You can’t get an approved retatrutide prescription yet, even if you’ve seen the name on a clinic’s website or in an online shop. Lilly, the company developing it, says it remains available through its clinical trials.
What’s different from Ozempic and Mounjaro?
These drugs work by activating receptors, the receiving points for hormone signals in your body. The difference is which signals they act on:
- Ozempic contains semaglutide, which activates the GLP-1 receptor.
- Mounjaro contains tirzepatide, which activates GLP-1 and GIP receptors.
- Retatrutide adds the glucagon receptor, making three targets in one molecule.
The MHRA’s guide to GLP-1 medicines explains how these treatments can help people feel fuller by mimicking a signal released after eating. Mounjaro also acts on a second signal involved in appetite and blood sugar. Retatrutide’s three-target design is why you’ll hear it called a “triple agonist.”
Those extra targets belong to one molecule, so retatrutide isn’t a blend of existing medicines. Our semaglutide and tirzepatide comparison explains those two medicines in more detail.
How much weight could it help people lose?
In the large TRIUMPH-1 trial, the highest-dose retatrutide group lost an estimated 25% of their starting weight over 80 weeks, compared with 3.9% for placebo. That’s around a quarter of starting body weight, which explains why the results drew attention. The participants had obesity or overweight with related health problems, without diabetes. Lilly’s trial report gives the results.
That average isn’t a target everyone should expect to reach. It also doesn’t tell someone already taking Ozempic or Mounjaro how much more they would lose by switching: this trial compared retatrutide with placebo. The question for a future prescription will be whether the benefits and side effects suit the person taking it.
If you’re using a prescribed GLP-1 medicine now, PepNote lets you log your weight and zoom out to see how it’s changed over weeks or months. You can also check your dose history in the same app, without trying to remember what you took and when.
What about side effects?
The weight-loss results come with familiar digestive side effects: nausea, diarrhea, constipation, and vomiting were among the most common problems in TRIUMPH-1. The trial also reported altered skin sensations, and some participants stopped treatment because of side effects.
When will it be available?
Lilly says it plans to apply for U.S. approval in early 2027. An application isn’t a launch date, so there’s no confirmed date when you’ll be able to collect it from a pharmacy.
Online listings don’t change that. The FDA warns against research-labeled products sold for people to use, whose quality is unknown. The approval decision, and then an actual launch announcement, are the milestones to watch.