If you've been following the weight-loss medicine revolution, you already know the big names: Ozempic and Wegovy (semaglutide), and Mounjaro and Zepbound (tirzepatide). Now a third contender is generating headlines that make even those look modest — Retatrutide, Eli Lilly's investigational "triple-G" agonist.
So how does Retatrutide actually stack up against the medications Australians already know? The short version: it works on more of the body's metabolic machinery at once, and in trials that has translated into the largest weight reductions ever recorded for a drug. Here's the detailed comparison.
One receptor, two, or three?
The single biggest difference between these medications is how many of the body's metabolic hormone receptors they activate.
| Medication | Active ingredient | Receptors targeted | Class |
|---|---|---|---|
| Ozempic / Wegovy | Semaglutide | 1 — GLP-1 | GLP-1 agonist |
| Mounjaro / Zepbound | Tirzepatide | 2 — GLP-1 + GIP | Dual agonist |
| Retatrutide | Retatrutide | 3 — GLP-1 + GIP + glucagon | Triple agonist |
- GLP-1 curbs appetite and slows how quickly your stomach empties, so you feel full for longer.
- GIP improves how your body handles insulin and metabolises fat.
- Glucagon — the receptor unique to Retatrutide — increases energy expenditure, so your body burns more, not just eats less.
That third pathway is why researchers describe Retatrutide as fundamentally different rather than simply "stronger." You can read how the triple mechanism works here.
Weight loss: the headline numbers
This is where the gap becomes obvious. Comparing across each drug's pivotal trials (different studies, so treat these as indicative rather than head-to-head):
| Medication | Average body weight lost | Trial |
|---|---|---|
| Semaglutide (Wegovy) | ~15% | STEP program |
| Tirzepatide (Mounjaro) | ~21% | SURMOUNT program |
| Retatrutide 12 mg | up to 28.3% | TRIUMPH-1 (80 weeks) |
In Retatrutide's landmark TRIUMPH-1 trial, 45.3% of participants on the highest dose lost 30% or more of their body weight — a level of loss previously seen only with bariatric surgery. And 65.3% of them dropped below a BMI of 30, meaning they no longer met the clinical definition of obesity. The full clinical trial results are broken down here.
More than a number on the scale
All three drugs do more than reduce weight, but Retatrutide's trial program has reported an unusually broad set of benefits in a single medication:
- Blood sugar — 90% of type 2 diabetes participants reached the ADA's target A1C
- Sleep apnoea — up to a 60.6% reduction in severity
- Knee osteoarthritis — pain scores reduced by up to 75.8%
- Cardiovascular markers — improvements in triglycerides, cholesterol and blood pressure
Semaglutide still holds the deepest cardiovascular outcomes evidence to date (its SELECT trial showed a 20% reduction in major cardiac events), which matters enormously for real-world prescribing. Retatrutide's cardiovascular outcomes data is still maturing.
Side effects: broadly similar
All three are based on gut-hormone biology, so the side-effect profiles rhyme: nausea, diarrhoea, constipation and vomiting, usually worst when starting or increasing the dose. In Retatrutide's trials these were generally manageable, though some analysts have noted adverse events were reported somewhat more often than with tirzepatide — not surprising for a more potent, three-pathway drug. Our safety overview covers this in detail.
The catch: availability
Here's the crucial difference for Australians right now.
- Ozempic, Wegovy and Mounjaro are TGA-approved and available (Wegovy was added to the PBS in January 2026 for severe obesity or cardiovascular history).
- Retatrutide is still investigational. It is not approved by the TGA or any regulator, and cannot be legally purchased. Eli Lilly plans to file for approval from 2027.
Momentum is building fast, though — Lilly announced positive topline results from two further pivotal trials, TRIUMPH-2 and TRIUMPH-3, in late July 2026. What that regulatory timeline means for Australia specifically is covered on our Australia page.
The bottom line
Ozempic proved the concept. Mounjaro raised the bar. Retatrutide, by adding a third receptor, appears to raise it again — delivering surgery-level weight loss alongside benefits across diabetes, sleep, joints and heart-health markers. The trade-off is timing: it's the most powerful option on paper, and the only one you can't get yet.
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Frequently asked questions
Is Retatrutide better than Mounjaro or Ozempic? In trials it has produced greater average weight loss, but it is not yet approved and hasn't been tested head-to-head against them in the same study. "Better" also depends on your goals and health profile — a conversation for a qualified doctor.
Can I get Retatrutide in Australia now? No. It is investigational and not approved by the TGA. Ozempic, Wegovy and Mounjaro are the approved options currently available.
When will Retatrutide be available? Eli Lilly plans to begin filing for regulatory approval from 2027. TGA review timing for Australia has not been announced.
This site is independent and not affiliated with Eli Lilly. Content is for general information only and is not medical advice. Always consult a qualified healthcare professional before making any decisions about your health or treatment.
