¹Clinical Trial: Retatrutide (LY3437943) in Adults with Obesity or Overweight (TRIUMPH-1).” Eli Lilly Clinical Trials Registry, https://trials.lilly.com/en-US/trial/405675. Accessed 27 Oct. 2025.
Retatrutide is being called the “next generation” weight loss injection. But what do the real results show so far?
Retatrutide is still in clinical testing, so no one can prescribe it yet. The early data has caught attention because participants in trials lost more weight than those on other medications like Wegovy or Mounjaro.
Below, we look at the verified trial results, what to expect in the first month, and why online “before and after” posts aren’t reliable evidence.
Key Takeaways
- Retatrutide achieved up to 28.7% average weight loss in phase 3 trials, higher than currently available treatments
- Weight loss begins early, with measurable changes within the first month
- The medication is still in clinical trials and not approved for prescription use anywhere
- Online sellers and influencer claims are unreliable. Buying retatrutide outside trials is illegal and dangerous
- Mounjaro, Wegovy, and orlistat are approved options available through licensed providers
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Retatrutide weight loss results: Phase 3 trials
The most up-to-date retatrutide weight loss results come from the first phase 3 clinical trial, TRIUMPH-4.
The trial included 445 adults with obesity (or overweight) and knee osteoarthritis. Participants received weekly injections for 68 weeks, with different dose groups compared to a placebo.
Average weight change at 68 weeks
Group
Average weight loss results
Retatrutide 9 mg
26.4%
Retatrutide 12 mg
28.7%
Placebo
2.1%
People on the highest dose lost nearly 29% of their body weight after 68 weeks. That's more than one-quarter of total body weight on average, the highest seen in any obesity treatment trial to date.
For comparison, the new 7.2mg dose of Wegovy (semaglutide) led to an average loss of 20.7% after 72 weeks, while Mounjaro (tirzepatide) trials reported around 22.5%.
Earlier Phase 2 results
Before the Phase 3 data, a Phase 2 trial with 338 adults showed promising results at 48 weeks. The trial included adults who had a body mass index (BMI) of 30 or higher, or 27 or higher with at least one weight-related condition.
Group
Average weight loss results
Retatrutide 1 mg
8.7%
Retatrutide 4 mg
17.1%
Retatrutide 8 mg
22.8%
Retatrutide 12 mg
24.2%
Placebo
2.1%
The Phase 3 results confirm and exceed these earlier findings, demonstrating consistent and substantial weight loss across trials.
Retatrutide 1-month results: What to expect early on
Early weight loss with retatrutide begins quickly. In the phase 2 study, participants started to see measurable changes within four weeks of treatment.
By week four, the average weight loss ranged from 2% to 5%, depending on the dose. This early change was similar to what’s seen in the first month of other weight loss injections like Wegovy.
Retatrutide helps with weight loss by mimicking three natural hormones (GLP-1, GIP and glucagon). These hormones work together to reduce hunger, slow digestion and increase the body’s use of stored fat.
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Other health effects seen in trials
Besides weight loss, trial participants saw improvements in:
- Blood sugar control (lower HbA1c levels)
- Blood pressure and cholesterol
- Liver fat reduction, which may help prevent fatty liver disease
These benefits were seen across doses but were strongest in higher-dose groups.
The early signals are encouraging, but we still need more evidence. Phase 3 clinical trials will help confirm the longer-term benefits and safety.
The risks of buying retatrutide online
Retatrutide is not yet approved for use in the UK. Clinical trials are ongoing, and the medication is only available to people taking part in those studies. Anyone claiming to use retatrutide outside a clinical trial cannot know for certain what they are taking.
On social media platforms like TikTok, you may see bodybuilders or gym-goers claiming to use retatrutide to “cut” or speed up results after a bulking phase (we cover this in more detail in our guide on retatrutide and bodybuilding).
These claims are unlikely to be true. People in those groups would not qualify for current clinical trials.
So if they are using something labelled as retatrutide, it has almost certainly been bought from illegal or unregulated sellers. It is illegal in the UK to sell retatrutide for human use as the drug has not yet been approved.
When you see “retatrutide results” online, keep these signs of hype in mind:
- Links to sellers or product pages claiming to offer retatrutide, even if labelled “for research only.” These are not authorised for human use.
- Payments through WhatsApp, Telegram or cryptocurrency, which are common signs of unregulated sales.
- Discount codes or promotional offers used to encourage purchase or use of an unapproved product.
- Videos or posts suggesting retatrutide sales are legal in the UK. The medicine is still unapproved and cannot be prescribed.
- Extreme diet advice or rapid-weight-loss claims that make progress look faster than it really is.
- Before-and-after photos that look exaggerated, often using lighting or filters.
- Influencers discussing combinations with other drugs, such as tirzepatide or steroids, which makes any results unreliable.
If you come across claims to sell “research peptides” or “retatrutide vials”, avoid them as they could be dangerous.
For verified information on safe and legal access, see our guide on where to buy retatrutide.
Retatrutide phase 3 results: What’s next?
Retatrutide is being studied in large phase 3 clinical trials known as the TRIUMPH studies, led by Eli Lilly. The first results are in. In December 2025, the TRIUMPH-4 trial showed retatrutide delivered 28.7% average weight loss at 68 weeks, along with significant improvements in knee pain.
Seven more TRIUMPH trials are expected to complete throughout 2026. These are testing retatrutide for weight management and related health conditions like type 2 diabetes and sleep apnoea.
If the remaining results confirm safety and effectiveness, retatrutide will then be reviewed by regulators such as the MHRA in the UK before it can be approved for prescription use. Approval would not be expected before mid-2026 at the earliest. Until that happens, it remains unavailable in the UK.
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Is retatrutide available in the UK? Safer options now
No, retatrutide is not available or licensed in the UK yet.
If you’re considering weight-loss medication, safe and approved alternatives include:
You can see how these options compare and review real Voy weight loss results.
