Reta is the nickname for retatrutide, an experimental weight loss drug developed by Eli Lilly. In the Phase 3 TRIUMPH-1 trial, people receiving the highest tested dose lost an average of 28.3% of their starting body weight over 80 weeks, equivalent to 70.3 pounds.
The figures come from the TRIUMPH-1 primary endpoint analysis, published in the New England Journal of Medicine. Researchers tested retatrutide in adults with obesity who did not have diabetes.
The comparison with Ozempic and Wegovy comes down to the drug mechanism. Semaglutide activates one hormone receptor, tirzepatide activates two, and retatrutide adds a third called glucagon. Researchers now have evidence of substantial weight reduction, although no direct trial has established that retatrutide produces better results than those established treatments.
Retatrutide is not FDA-approved. Eli Lilly is still developing the treatment, and the FDA has warned companies against marketing unapproved retatrutide products. Vials advertised online as Reta should not be confused with the investigational medication administered under medical supervision in clinical trials.
An average weight reduction of 28.3% would represent a major advance in medical obesity treatment if the results translate into an approved medication that patients can tolerate over the long term. The next challenge is establishing its safety and determining how patients maintain their weight loss after treatment.
How Effective Is Reta for Weight Loss?
Retatrutide is an experimental once-weekly injection that activates receptors for three hormones known as GLP-1, GIP and glucagon. The combination influences appetite, blood sugar regulation and energy metabolism.
Each hormone acts through a separate receptor, although their effects overlap.
- GLP-1 helps regulate appetite, food intake and insulin release.
- GIP contributes to insulin signaling and metabolic regulation.
- Glucagon influences glucose production and energy metabolism.
Semaglutide, the active ingredient in Ozempic and Wegovy, targets GLP-1 receptors. Tirzepatide, sold as Mounjaro and Zepbound, activates GLP-1 and GIP receptors.
Retatrutide adds glucagon receptor activation to those pathways. Researchers are studying the combined effect because glucagon signaling has a role in energy expenditure as well as glucose metabolism.
The Phase 3 results show substantial weight reduction, particularly at higher doses. The clinical benefit is considerable, but gastrointestinal side effects and treatment discontinuations remain an important part of evaluating the drug.
How Much Weight Can You Lose on Retatrutide?
Participants receiving 12 mg of retatrutide lost an average of 28.3% of their body weight over 80 weeks. TRIUMPH-1, a randomized, double-blind Phase 3 study of adults with obesity but without diabetes, produced the result.
Researchers compared weekly injections of 4 mg, 9 mg and 12 mg against placebo. Weight loss increased across the tested doses, with the highest-dose group recording the largest average reduction.
| TRIUMPH-1 Finding | Reported Result |
|---|---|
| Study duration | 80 weeks |
| Study population | Adults with obesity, without diabetes |
| Highest dose studied | 12 mg weekly |
| Average weight loss at 12 mg | 28.3% |
| Average weight loss in pounds | 70.3 pounds |
| Participants at 12 mg losing at least 30% | 45.3% |
Source: Eli Lilly TRIUMPH-1 results, May 21, 2026, efficacy table, primary endpoint and key secondary endpoints. The 28.3%, 70.3-pound and 45.3% figures refer to the 12 mg group in the reported efficacy analysis.
At a starting weight of 250 pounds, a 28.3% reduction equals about 70.8 pounds. At 300 pounds, it equals 84.9 pounds. These examples illustrate the scale of the average response, although individual outcomes varied in the trial.
Nearly half of participants receiving 12 mg lost at least 30% of their starting body weight. Specifically, 45.3% reached that threshold, compared with 0.5% in the placebo group.
Researchers then followed selected participants for another 24 weeks. Among those with a starting BMI of at least 35 who continued into the extension, the highest-dose group reached an average reduction of 30.3% at 104 weeks.
The June 6 Eli Lilly trial update reported an average loss of 85 pounds in that extension group. Participants had completed the initial treatment period and tolerated their assigned medication before continuing.
The 30.3% result is particularly encouraging for patients who remain on therapy. However, the extension included selected participants rather than the original full trial population, so the 80-week findings remain the stronger basis for estimating the overall treatment response.
Retatrutide Also Produced Major Weight Loss in People With Type 2 Diabetes
People with type 2 diabetes have generally recorded smaller average weight reductions in obesity medication trials than participants without diabetes. Retatrutide followed that trend, but the reductions remained substantial.
TRIUMPH-2 enrolled 1,152 adults with overweight or obesity and type 2 diabetes. Over 80 weeks, researchers measured changes in weight and blood sugar among participants assigned to retatrutide or placebo.
The TRIUMPH-2 study published in The Lancet reported the following weight-loss results using its treatment-regimen analysis.
| Weekly Treatment | Average Weight Loss at 80 Weeks |
|---|---|
| Retatrutide 4 mg | 11.9% |
| Retatrutide 9 mg | 16.8% |
| Retatrutide 12 mg | 18.8% |
| Placebo | 5.1% |
Source: TRIUMPH-2 published abstract, PubMed PMID 42810372, Findings section, primary body-weight endpoint and treatment-regimen estimates.
The highest dose produced an estimated weight reduction 13.8 percentage points greater than placebo. The reported 95% confidence interval for that treatment difference extended from 11.8 to 15.8 percentage points.
Among participants receiving 12 mg, 47% lost at least 20% of their starting weight and 31% lost at least 25%. The corresponding placebo figures were 6% and 3%.
Blood sugar results also favored retatrutide. At 12 mg, HbA1c fell by an average of 1.45 percentage points, compared with 0.45 percentage points on placebo. HbA1c measures average blood sugar over roughly the preceding two to three months.
By the end of the study, 72% of participants receiving the highest dose had reached an HbA1c of 6.5% or lower, compared with 29% in the placebo group.
The combination of weight reduction and improved blood sugar is clinically significant for people managing both obesity and type 2 diabetes. Retatrutide has demonstrated effects on both outcomes, although the FDA has yet to determine its approved uses.
The Exact Numbers Related to Eficacy Depends on the Analysis
Readers following the TRIUMPH-2 results may have seen two figures for weight loss at the highest dose. Eli Lilly reported 20.8% in its initial July announcement, but the later peer-reviewed publication reported 18.8%.
The figures come from separate statistical analyses of the same clinical trial. The July result used an efficacy analysis based on specified assumptions about treatment adherence and continuation.
The September publication reported the treatment-regimen analysis, which accounts for participants regardless of treatment discontinuation or use of other interventions under the study methodology.
Eli Lilly presented the earlier estimate in its July 23 trial announcement. The release also included findings from TRIUMPH-3, a separate study involving adults with severe obesity and established cardiovascular disease.
Both percentages are legitimate reported results, but they describe separate statistical approaches. For patients considering long-term treatment, the analysis that accounts for treatment discontinuation provides useful information alongside the efficacy estimate.
Differences Between Ozempic, Zepbound and Reta
The main difference among the medicines is their hormone receptor activity.
Ozempic and Wegovy contain semaglutide, which activates GLP-1 receptors. Mounjaro and Zepbound contain tirzepatide, which activates GLP-1 and GIP receptors.
Retatrutide adds glucagon receptor activity to both pathways.
| Medication | Active Ingredient | Hormone Receptors Targeted | U.S. Regulatory Position |
|---|---|---|---|
| Ozempic | Semaglutide | GLP-1 | FDA-approved |
| Wegovy | Semaglutide | GLP-1 | FDA-approved |
| Mounjaro | Tirzepatide | GLP-1 and GIP | FDA-approved |
| Zepbound | Tirzepatide | GLP-1 and GIP | FDA-approved |
| Retatrutide, or Reta | Retatrutide | GLP-1, GIP and glucagon | Investigational, not FDA-approved |
Ozempic and Mounjaro have approved indications for type 2 diabetes. Wegovy and Zepbound are approved for chronic weight management and certain additional indications. Retatrutide currently has no FDA-approved indication.
Existing treatments already have a substantial patient base. We previously reported that 15% of American women use GLP-1 medications, based on national survey estimates.
A third hormone receptor does not automatically establish a better treatment. TRIUMPH-1 and TRIUMPH-2 tested retatrutide against placebo, not directly against Ozempic or Zepbound.
For clinicians, the decisive comparison would involve patients randomized to retatrutide or an established obesity medication under the same study conditions. Until those results are available, the trial percentages alone cannot establish which drug offers the strongest balance of weight reduction and tolerability.
What Are the Side Effects of Retatrutide?
Between 27% and 34% of participants taking retatrutide in TRIUMPH-2 reported diarrhea, compared with 13% receiving placebo. Nausea affected 14% to 28% of the retatrutide groups, against 8% on placebo.
The study also recorded low blood pressure-related events and dysesthesia, a term for abnormal sensations such as tingling, burning or skin discomfort.
| Reported Adverse Event | Retatrutide Groups | Placebo Group |
|---|---|---|
| Diarrhea | 27% to 34% | 13% |
| Nausea | 14% to 28% | 8% |
| Low blood pressure-related events | 1% to 6% | Less than 1% |
| Dysesthesia | 4% to 7% | 1% |
| Permanent discontinuation due to adverse events or death | 4% to 12% | 5% |
Source: TRIUMPH-2, The Lancet, published safety findings and adverse-event analysis. Percentages are rounded from the reported treatment groups. Additional classifications appear in the study tables and supplementary materials.
Permanent treatment discontinuation due to adverse events or death affected 4% of participants assigned to 4 mg, 12% assigned to 9 mg and 8% assigned to 12 mg. The placebo figure was 5%.
Seven participants died during the trial, including six assigned to retatrutide and one assigned to placebo. Investigators assessed all seven deaths as unrelated to the intervention as they all died of natural causes. The number of events was too small to establish the long-term risk of rare outcomes.
Researchers also reported that 965 of the 1,152 randomized participants, or 84%, completed the study drug.
The weight-loss benefit is substantial enough to justify continued clinical development, despite the gastrointestinal side effects recorded in the trials. For a patient with severe obesity and related health complications, an average reduction approaching 28% could be clinically valuable. However, a treatment that causes persistent symptoms or forces discontinuation will not deliver the same benefit to everyone.
The 80-week trials provide a substantial safety record, but patients may eventually remain on obesity medication for many years. Cardiovascular outcomes, pancreatitis and other uncommon serious events still need continued evaluation. Researchers also have not established how much weight patients regain after stopping retatrutide.
Retatrutide Is Still Awaiting FDA Approval
Retatrutide remains an investigational drug without FDA approval. Eli Lilly has reported positive results from several Phase 3 studies and plans to submit a Biologics License Application in the first quarter of 2027, but regulators have not authorized the medicine for routine prescription use or announced a commercial release date.
FDA reviewers will assess effectiveness, safety, manufacturing and the proposed prescribing information. The agency can approve the treatment, request additional information or decline approval based on its evaluation.
Until that process is complete, there is no approved retail formulation, official prescribing label or confirmed commercial price for retatrutide.
Why Is Reta Already Being Sold Online If It Is Not Approved?
Online sellers have advertised products under names such as Reta, retatrutide peptide and research retatrutide. Some listings use coded descriptions resembling the hormone combinations found in obesity medications.
The FDA warning on unapproved GLP-1 drugs explicitly states that retatrutide cannot legally be used in compounding. The agency has not found retatrutide safe and effective for any condition through the drug approval process.
Do not inject a vial sold online as Reta. A seller using the retatrutide name cannot establish that its product has the identity, purity, strength or sterility of the investigational drug used in clinical trials. A label describing the vial as a research peptide does not make it safe for human injection.
The FDA has already identified specific businesses marketing unapproved retatrutide products. On March 31, 2026, the agency issued a warning letter to Gram Peptides, naming retatrutide among the products advertised through its website.
Five additional warning letters dated August 24, 2026, addressed sellers whose listings included retatrutide or coded versions of the compound. The recipients were:
- NuScience Peptides LLC
- Peptide Partners LLC
- TXP Innovations LLC, operating as Tex Peptides
- Royal Peptides LLC
- Peak Performance Peptides
Those six dated letters are documented examples, not a complete count of every FDA action involving retatrutide. The agency has also pursued other businesses advertising unapproved weight loss products.
Injectable products carry particular risks if they have not been manufactured and handled under appropriate quality controls. Contamination, incorrect concentrations or unidentified ingredients can expose consumers to harm that was not evaluated in clinical trials.
Regulatory concerns have affected other weight loss products as well. NCHStats previously covered how Hims & Hers withdrew its copycat Wegovy pill following legal pressure and FDA scrutiny. Retatrutide presents an additional concern because no product containing the active drug has received FDA approval.
When Will Retatrutide Be Available by Prescription?
Patients cannot currently obtain an FDA-approved retatrutide prescription through the standard U.S. pharmacy market. Eligible volunteers can instead receive the investigational medication through authorized clinical trials, where researchers control the drug supply and monitor participants.
Current studies and recruitment information are listed in the official ClinicalTrials.gov retatrutide records. Eligibility depends on each study protocol, and recruitment status changes as enrollment progresses.
Eli Lilly plans to submit its FDA application in the first quarter of 2027. Any commercial launch will depend on the regulatory review and final FDA decision.
No approved retail price or insurance coverage policy has been announced. Predictions about pharmacy availability and monthly treatment costs remain speculative until the company or regulators provide confirmed information.
For patients interested in experimental treatment, an authorized clinical trial offers medical supervision and a controlled drug supply. Buying an online peptide sold as Reta provides neither safeguard.
The Biggest Unanswered Question Is What Happens After Treatment Stops
The 28.3% average weight reduction reported in TRIUMPH-1 is a substantial result. TRIUMPH-2 also found meaningful weight loss and improved blood sugar among participants with type 2 diabetes. If the FDA approves retatrutide, the drug could become an important additional option for obesity treatment.
The potential patient population is large. Federal data in our U.S. weight and obesity statistics show that 40.3% of American adults had obesity during the August 2021 to August 2023 measurement period, including 9.4% with severe obesity.
Researchers are investigating retatrutide in additional obesity-related conditions, including obstructive sleep apnea and knee osteoarthritis. Those studies will help establish the clinical benefits associated with weight reduction.
One of the most consequential unanswered questions concerns weight regain after treatment ends. The 80-week results establish how much weight participants lost during treatment. They do not establish how much weight patients would retain after discontinuing the drug or how many would need ongoing medication to maintain the reduction.
The answer has financial consequences as well as medical ones. Insurers considering long-term coverage need evidence of sustained benefits and health outcomes, not only the percentage of weight lost during a trial. Patients also need reliable information about the consequences of stopping treatment because of cost, side effects or another medical condition.
The published studies also provide important safety information, but longer observation is needed to characterize uncommon adverse events and outcomes associated with extended treatment.
Both TRIUMPH-1 and TRIUMPH-2 were funded by Eli Lilly, and the papers disclose financial relationships involving company employees and shareholders. Independent analysis, regulatory scrutiny and additional research will help determine the role of retatrutide in clinical practice.
Retatrutide has demonstrated substantial weight loss in clinical trials, but maintaining those reductions after stopping treatment remains an unanswered question. Resolving that issue will be central to evaluating its long-term value for patients, clinicians and insurers. Until then, retatrutide remains a promising investigational drug rather than an approved treatment.
Editorial information: This article is based on peer-reviewed clinical research, manufacturer trial announcements and FDA enforcement records. Product website links are included for identification and comparison, not as purchase recommendations. No sponsorship or affiliate relationship is represented in this article.
