Retatrutide trials results show up to 28.7% weight loss in Phase 3. Compare Phase 2 NEJM data, TRIUMPH-1 findings, safety, and what's next for this drug.
Retatrutide trials results show that this investigational triple-hormone receptor agonist produces substantial weight loss and metabolic improvements in people with obesity and type 2 diabetes. In the Phase 2 trial published in the New England Journal of Medicine (NEJM), the highest dose led to an average 24.2% weight reduction at 48 weeks. The Phase 3 TRIUMPH-1 trial later reported up to 28.7% weight loss at 68 weeks. Retatrutide is not yet approved by the FDA for any use.
What Is Retatrutide and How Does It Work?
Retatrutide is an experimental once-weekly injectable medication developed by Eli Lilly. It activates three hormone receptors: GIP, GLP-1, and glucagon. This triple agonist approach is designed to reduce appetite, slow gastric emptying, and increase energy expenditure.
Unlike semaglutide (GLP-1 only) or tirzepatide (GIP/GLP-1), retatrutide adds glucagon receptor agonism, which may contribute to greater fat loss. Many researchers examine how this mechanism translates into clinical outcomes.
Phase 2 Trial Results: The NEJM Retatrutide Study
The Phase 2 trial enrolled 338 adults with obesity or overweight without diabetes. Participants received weekly injections of retatrutide (1 mg, 4 mg, 8 mg, or 12 mg) or placebo for 48 weeks. The results, published in NEJM in 2023, were striking:
- 12 mg dose: average weight loss of 24.2%
- 8 mg dose: average weight loss of 22.8%
- 4 mg dose: average weight loss of 17.0%
- Placebo: average weight loss of 2.1%
At 48 weeks, 100% of participants taking 12 mg lost at least 5% of their body weight, and 83% lost at least 20%. The trial also showed improvements in waist circumference, triglycerides, and HbA1c. These retatrutide results set high expectations for Phase 3.
Phase 3 TRIUMPH Program: TRIUMPH-1 and TRIUMPH-3 Updates
The Eli Lilly Phase 3 trial retatrutide program, known as TRIUMPH, includes several large trials. TRIUMPH-1 evaluates retatrutide in adults with obesity or overweight with weight-related conditions. In June 2025, Eli Lilly announced topline results from the TRIUMPH-1 trial of retatrutide: participants taking 12 mg achieved an average 28.7% weight loss at 68 weeks. This retatrutide new study also reported that 86% of participants lost at least 20% of their body weight and 50% lost at least 30%. Full data are pending peer review and presentation at medical conferences.
TRIUMPH-3 retatrutide trial is another Phase 3 study that focuses on a different population, such as people with obesity and obstructive sleep apnea. For those tracking clinical trials retatrutide, the full TRIUMPH data are expected to be published in the coming years.
How Retatrutide Results Compare to Other Weight Loss Medications
Comparing results across trials requires caution because study designs, populations, and durations differ. Still, the following table summarizes average weight loss from key trials.
| Medication | Mechanism | Average Weight Loss | Trial Duration |
|---|---|---|---|
| Semaglutide 2.4 mg (Wegovy) | GLP-1 | ~15% | 68 weeks |
| Tirzepatide 15 mg (Zepbound) | GIP/GLP-1 | ~21% | 72 weeks |
| Retatrutide 12 mg (Phase 2) | GIP/GLP-1/glucagon | 24.2% | 48 weeks |
| Retatrutide 12 mg (Phase 3 TRIUMPH-1) | GIP/GLP-1/glucagon | 28.7% | 68 weeks |
These numbers are averages; individual results vary. For a different investigational peptide, aod 9604 vs retatrutide comparisons often appear online, but the two have very different mechanisms and evidence levels. AOD 9604 is a fragment of human growth hormone and has far less clinical data for weight loss.
Safety and Side Effects Reported in Retatrutide Trials
Across Phase 2 and Phase 3 trials, the most common side effects were gastrointestinal. They included nausea, diarrhea, vomiting, and constipation. These effects were generally mild to moderate and often decreased over time.
Some participants experienced increases in heart rate and liver enzymes. A small number of participants discontinued treatment due to side effects. As with any investigational drug, long-term safety data are still being collected. Anyone considering retatrutide outside of a clinical trial should talk to a healthcare professional.
Many people share their experiences on reddit retatrutide results, but anecdotal reports are not a substitute for controlled trial data. When reading about retatrutide online, verify that the information comes from peer-reviewed studies or official trial announcements.
What Retatrutide Trial Results Mean for Future Availability
Retatrutide is not FDA-approved, and it is not legally available by prescription in the United States. If the Phase 3 program continues to meet its endpoints, Eli Lilly is expected to submit a New Drug Application to the FDA. That process could take years, and approval is not guaranteed.
Questions like how much bac water for 10 mg retatrutide are common among people handling the peptide outside of clinical settings. However, retatrutide is not approved for human use, and dosing information from trials does not translate to safe self-administration. A do-it-yourself approach carries significant risks, including infection and improper dosing.
Frequently Asked Questions
What did the TRIUMPH-1 trial find for retatrutide?
The TRIUMPH-1 Phase 3 trial reported that participants taking 12 mg of retatrutide lost an average of 28.7% of their body weight at 68 weeks. The company also stated that 86% of participants lost at least 20% and 50% lost at least 30%. These results are topline and have not yet been fully peer-reviewed. Retatrutide remains investigational.
Is retatrutide FDA-approved?
No, retatrutide is not approved by the FDA for any indication. It is an investigational drug available only through clinical trials. People should not purchase or use retatrutide outside of a supervised trial setting.
How does retatrutide compare to tirzepatide for weight loss?
In separate clinical trials, retatrutide 12 mg produced greater average weight loss than tirzepatide 15 mg (28.7% vs about 21% at similar time points). However, no head-to-head trial has directly compared the two drugs. Both can cause gastrointestinal side effects, and individual results vary.
This page provides educational research information and does not replace medical advice, diagnosis, or treatment.