Retatrutide: The Complete Guide to the Triple Agonist
Retatrutide is the most potent weight loss peptide ever tested in clinical trials. The world's first triple hormone receptor agonist, targeting GLP-1, GIP, and glucagon simultaneously, delivered an average of 28.3% body weight lost (70.3 lbs) at 80 weeks in TRIUMPH-1, the pivotal Phase 3 obesity trial. It is not yet FDA-approved and cannot be prescribed. ADA 2026 data also showed 65.3% of 12 mg participants reached BMI below 30, 33.3% reached BMI below 25, and a nested obstructive sleep apnea trial showed up to a 60.6% reduction in apnea-hypopnea events.
Retatrutide is not FDA-approved and cannot be prescribed.
It is only available through clinical trial enrollment. The information on this page is for educational purposes only. Consult a healthcare provider for treatment options.
Key Facts at a Glance
- Drug class
- Triple GIP/GLP-1/Glucagon receptor agonist
- Administration
- Once-weekly subcutaneous injection
- FDA approval
- Not yet approved, Phase 3 trials
- Average loss
- 28.3% body weight (80 wks, TRIUMPH-1)
- OSA signal
- 60.6% AHI reduction in nested TRIUMPH-1 basket trial
- Manufacturer
- Eli Lilly
- Expected filing
- Potentially 2027 (pending remaining trials)
- Trial doses
- 1 mg, 4 mg, 8 mg, 9 mg, 12 mg
- Brand name
- None yet (investigational)
Table of Contents
What Is Retatrutide?
Retatrutide (LY3437943) is an investigational synthetic peptide developed by Eli Lilly. It activates three incretin and metabolic hormone receptors simultaneously:
- GLP-1Appetite suppression, gastric slowing (shared with semaglutide and tirzepatide)
- GIPEnhanced insulin response, metabolic regulation (shared with tirzepatide)
- GlucagonPromotes fat burning, increases energy expenditure (unique to retatrutide)
No other approved or late-stage medication targets all three pathways. This triple mechanism is why retatrutide has produced more weight loss than semaglutide or tirzepatide in their respective trials. For a deeper look at currently available options, see our tirzepatide vs. semaglutide comparison.
How Does Retatrutide Work?
Retatrutide combines and extends the mechanisms of its predecessors, adding a third dimension that prior GLP-1 drugs can't match:
GLP-1 Receptor Activation
Suppresses appetite via the hypothalamus, delays gastric emptying, enhances glucose-dependent insulin secretion, and reduces glucagon when blood sugar is high. The same pathways semaglutide and tirzepatide use.
GIP Receptor Activation
Enhances GLP-1's appetite-suppressing effects, improves insulin sensitivity, and contributes additional metabolic regulation. Tirzepatide also uses this pathway, which is why it outperforms semaglutide.
Glucagon Receptor Activation: The Third Dimension
This is what sets retatrutide apart from everything else:
- Increases energy expenditure: glucagon signals the body to burn more energy, even at rest
- Promotes fat oxidation: signals the liver to break down stored fat for fuel
- Reduces liver fat: Phase 2 showed dramatic liver fat reduction (relevant for MASLD/NAFLD)
- Thermogenic effects: may increase basal metabolic rate
Why Three Is Better Than Two
Semaglutide (GLP-1) primarily reduces how much you eat. Tirzepatide (GLP-1 + GIP) does that better. Retatrutide attacks obesity from both sides. It reduces intake AND increases energy expenditure. This dual mechanism is why weight loss curves in retatrutide trials showed no plateau at 48 weeks, unlike semaglutide and tirzepatide where loss typically plateaus around 6–9 months.
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Clinical Trial Evidence
Phase 2 Trial (2023)
Published in the New England Journal of Medicine (2023). 338 adults with obesity (no diabetes), randomized across multiple dose arms, 48 weeks.
Results at 24 weeks:
| Dose | Weight Loss at 24 weeks |
|---|---|
| 1 mg | −7.2% |
| 4 mg | −12.9% |
| 8 mg | −17.3% |
| 12 mg | −17.5% |
| Placebo | −1.6% |
Results at 48 weeks (secondary endpoint):
| Dose | Weight Loss at 48 weeks |
|---|---|
| 8 mg | −22.8% |
| 12 mg | −24.2%(best dose) |
| Placebo | −2.1% |
TRIUMPH-4: First Phase 3 Results (December 2025)
The TRIUMPH clinical program enrolled approximately 5,800 participants across 8 Phase 3 trials. TRIUMPH-4 was the first to report results.
Design: Adults with obesity/overweight AND knee osteoarthritis. Duration: 68 weeks. Doses: 9 mg and 12 mg.
| Metric | 9 mg Dose | 12 mg Dose | Placebo |
|---|---|---|---|
| Avg. weight loss | ~22% | 28.7% | ~2% |
| Avg. pounds lost | Not reported | 71.2 lbs | Not reported |
| Placebo-adjusted loss | Not reported | 26.6% | Not reported |
| OA pain reduction | Significant | 75% | Not reported |
These are strong Phase 3 results, but TRIUMPH-4 studied a specific osteoarthritis population rather than the primary obesity trial population.
TRIUMPH-1: Pivotal Phase 3 Obesity Results (May 2026)
TRIUMPH-1 is the pivotal obesity trial investors and clinicians were waiting for. Lilly reported topline results in May 2026 from adults with obesity or overweight and at least one weight-related comorbidity, without diabetes. ClinicalTrials.gov lists TRIUMPH-1 as NCT05929066, a randomized, double-blind, placebo-controlled Phase 3 study. Lilly reported 2,339 randomized participants in the master trial.
| Group | Mean weight loss at 80 weeks | Pounds / kg lost | Lost at least 30% |
|---|---|---|---|
| Retatrutide 4 mg | 19.0% | 47.2 lb / 21.4 kg | 15.3% |
| Retatrutide 9 mg | 25.9% | 64.4 lb / 29.2 kg | 37.9% |
| Retatrutide 12 mg | 28.3% | 70.3 lb / 31.9 kg | 45.3% |
| Placebo | 2.2% | 5.5 lb / 2.5 kg | 0.5% |
ADA 2026: BMI Normalization, OSA, and Knee Pain Basket Data
At the American Diabetes Association 86th Scientific Sessions in June 2026, Lilly presented additional TRIUMPH-1 data beyond the topline weight-loss table. The most clinically important update is that retatrutide did not just lower average weight. Many participants crossed BMI thresholds used to define obesity and healthy-range weight.
| ADA 2026 endpoint | Result | Why it matters |
|---|---|---|
| BMI below 30 on 12 mg | 65.3% | No longer met BMI criteria for obesity at 80 weeks |
| BMI below 25 on 12 mg | 33.3% | Reached the conventional healthy BMI range |
| AHI change in moderate-to-severe OSA | -36.1 events/hr, 60.6% | Large reduction in obstructive sleep apnea severity from a 58.6 events/hr baseline |
| WOMAC knee pain change | -4.3 points, 73.1% | Large osteoarthritis pain reduction from a 6.0-point baseline |
The OSA and knee pain findings came from nested TRIUMPH-1 basket trials, not from an FDA-approved indication. They strengthen the obesity-complication signal, but retatrutide remains investigational.
Upcoming TRIUMPH Trial Readouts
More Phase 3 data are still expected by end of 2026:
| Trial | Population |
|---|---|
| TRIUMPH-2 | Obesity with type 2 diabetes |
| TRIUMPH-3 | Obesity maintenance |
| TRIUMPH-5 | Obstructive sleep apnea follow-up program data |
| TRIUMPH-6/7/8 | Additional indications and populations |
TRANSCEND-T2D-1: Type 2 Diabetes Results (ADA 2026)
Eli Lilly announced top-line TRANSCEND-T2D-1 results in March 2026, then presented additional data at ADA 2026 with simultaneous publication in The Lancet. This was the first Phase 3 trial of retatrutide specifically in adults with type 2 diabetes (T2D). It is distinct from the TRIUMPH program, which focused on obesity without T2D as its primary criterion.
Trial Design
Phase 3, 40-week, randomized, double-blind, placebo-controlled. 537 participants randomized 1:1:1:1 to retatrutide 4 mg, 9 mg, 12 mg, or placebo. Baseline A1C: 7.9%; baseline BMI: 35.8 kg/m².
A1C Reduction at 40 Weeks (Primary Endpoint)
| Dose | A1C Reduction | Weight Loss | Pounds Lost |
|---|---|---|---|
| Retatrutide 4 mg | -1.7% | -11.5% | -24.5 lbs |
| Retatrutide 9 mg | -2.0% | -15.5% | -33.3 lbs |
| Retatrutide 12 mg | -1.9% | -16.8% | -36.6 lbs |
| Placebo | -0.8% | -2.5% | -6.2 lbs |
A1C Target and Normalization Rates
ADA 2026 added the clinically useful responder data. These figures matter because they show how many participants crossed treatment targets, not just the average A1C change.
| A1C threshold | Retatrutide result | Interpretation |
|---|---|---|
| Below 7.0% | Up to 90% | Met the ADA general glycemic target for many adults with T2D |
| 6.5% or below | Up to 85% | Reached a stricter target often considered for earlier disease when safe |
| Below 5.7% | Up to 46% | Reached normoglycemia, the conventional non-diabetes A1C range |
Cardiovascular Risk Factor Improvements
Eli Lilly reported clinically meaningful improvements across key cardiovascular risk factors:
- Non-HDL cholesterol: reduced significantly vs. placebo
- Triglycerides: reduced significantly vs. placebo
- Systolic blood pressure: improved vs. baseline
ADA 2026 data reported reductions up to 39.6% in triglycerides, 19.8% in non-HDL cholesterol, 6.4 mmHg in systolic blood pressure, and 4.9 inches in waist circumference at 40 weeks.
Safety Profile in T2D Population
| Side Effect | Rate (retatrutide) | Rate (placebo) |
|---|---|---|
| Nausea | 16.4–26.5% | 3.7% |
| Diarrhea | 18.7–26.3% | 4.5% |
| Vomiting | 15.7–17.6% | 2.2% |
| Dysesthesia | 2.3–4.5% | 0.0% |
| Treatment discontinuation | 2.2–5.1% | 0% |
Notably, dysesthesia rates in the T2D population (2.3-4.5%) were substantially lower than in the obesity-only TRIUMPH-4 trial (8.8-20.9%). Discontinuation rates were also much lower (2.2-5.1% vs 12.2-18.2%). The T2D population may tolerate retatrutide better, or the shorter 40-week duration may account for some of the difference.
What this means for T2D patients
For people with type 2 diabetes who also have obesity, retatrutide offers a meaningful advantage over existing options: A1C reductions of 1.7-2.0% combined with 11.5-16.8% body weight loss in 40 weeks. Current best-in-class agents (tirzepatide, semaglutide) achieve roughly 1.5-2.0% A1C reduction and 8-15% weight loss in T2D populations. Retatrutide's weight loss ceiling appears higher, though it remains unapproved and patient-specific prescribing guidance does not exist yet.
Current Status: Where Does Retatrutide Stand?
As of June 2026:
- ❌NOT FDA-approved, still in Phase 3 trials
- ✅Phase 3 TRIUMPH-4 showed positive results (December 2025)
- ✅TRANSCEND-T2D-1 Phase 3 showed positive A1C and weight loss results in T2D patients (March 2026)
- ✅ADA 2026 data showed nested OSA and knee osteoarthritis improvements, plus detailed A1C target results
- 🔄Additional Phase 3 trials reporting through end of 2026
- 📋FDA filing likely in 2027 at the earliest
How to access retatrutide today
You cannot get a prescription for retatrutide. It's only available through clinical trial enrollment. Research peptide vendors sell it labeled “for research use only” but this carries significant risk: no quality assurance, no medical oversight, and uncertain purity. We strongly recommend waiting for an approved product.
Availability and Safety FAQ: What We Know vs. What We Do Not
The short answer: retatrutide is promising, but it is still investigational. Phase 2 and early Phase 3 data are not the same thing as approved prescribing guidance, real-world safety monitoring, or a legal consumer market.
Evidence we can cite
- Phase 2 obesity trial: 338 adults, up to 17.5% mean weight loss at 24 weeks and 24.2% at 48 weeks.
- TRIUMPH-1: 2,339 adults without diabetes, 28.3% mean weight loss at 80 weeks on 12 mg, 65.3% reaching BMI below 30, and 33.3% reaching BMI below 25.
- TRIUMPH-1 basket trials: 60.6% reduction in moderate-to-severe OSA severity and 73.1% reduction in knee osteoarthritis pain.
- TRIUMPH-4: 445 adults with obesity or overweight and knee osteoarthritis, 28.7% mean weight loss at 68 weeks on 12 mg.
- TRANSCEND-T2D-1: 537 adults with type 2 diabetes, A1C reductions of 1.7% to 2.0%, weight loss up to 16.8% at 40 weeks, and up to 46% achieving A1C below 5.7%.
Evidence we do not have yet
- No FDA-approved label, no approved dose schedule, and no prescribing information.
- No peer-reviewed Phase 3 obesity publication yet for TRIUMPH-1 or TRIUMPH-4, only company-presented data and press releases.
- No real-world safety database comparable to approved GLP-1 medications.
- No proven maintenance, reset, or discontinuation strategy after large weight loss.
Can you get retatrutide outside a trial?
Not as a legitimate prescription medication. FDA materials on unapproved GLP-1 drugs state that retatrutide and cagrilintide cannot be used in compounding under federal law. FDA warning letters in 2025 and 2026 also described marketed retatrutide products as unapproved new drugs or misbranded products when sold for human use. Clinical trial enrollment remains the legitimate access route before approval.
Do Reddit or progress-photo reports count as real-world evidence?
No. They can show demand and surface safety questions, but they cannot prove efficacy or safety. Forum posts usually do not verify the compound, concentration, dosing, medical history, adverse events, or whether the person used other drugs at the same time.
Treat anecdotes as anecdotes. The best current evidence is still Jastreboff et al. in NEJM, Lilly's Phase 3 topline releases, ClinicalTrials.gov records, and the TRIUMPH program design paper by Giblin et al. in Diabetes, Obesity and Metabolism.
What about thyroid conditions?
This is an uncertainty zone. Retatrutide has not completed FDA review, and condition-specific guidance for thyroid nodules, thyroid cancer history, elevated calcitonin, MEN2, or active thyroid disease is not established. Because approved GLP-1 class labels carry thyroid C-cell tumor warnings based on rodent findings, anyone with a thyroid condition should involve an endocrinologist and should not use non-prescribed research products.
Can retatrutide reset metabolism, then be stopped?
There is no clinical evidence for a retatrutide reset strategy. Approved GLP-1 data show that weight commonly returns after stopping treatment, and retatrutide does not yet have published discontinuation data. Until maintenance and withdrawal results are available, the safer assumption is that retatrutide would be a chronic obesity medication if approved, not a short cycle.
Side Effects & Safety
New Safety Signal: Dysesthesia
Phase 3 trials confirmed a side effect not seen prominently in Phase 2: dysesthesia, abnormal sensation including tingling, burning, or unusual perception of touch.
- • TRIUMPH-1: 5.1% on 4 mg, 12.3% on 9 mg, 12.5% on 12 mg, vs. 0.9% placebo
- • TRIUMPH-4: 8.8% on 9 mg and 20.9% on 12 mg, vs. 0.7% placebo
- • TRANSCEND-T2D-1: 2.3% to 4.5% across retatrutide doses, vs. 0.0% placebo
Lilly reported that most dysesthesia events were mild to moderate, the majority resolved during treatment, and most participants continued taking retatrutide. The signal still matters because it appears dose-related and is not typical for approved GLP-1 drugs.
TRIUMPH-1 GI Side Effects and Discontinuation
In the pivotal TRIUMPH-1 obesity trial, GI side effects increased with dose and were generally consistent with other incretin-based therapies, but the 12 mg arm had a higher discontinuation rate than placebo:
| Side Effect | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Nausea | 28.6% | 38.4% | 42.4% | 14.8% |
| Diarrhea | 25.2% | 34.1% | 32.0% | 13.5% |
| Constipation | 23.8% | 25.9% | 26.1% | 10.9% |
| Vomiting | 10.6% | 22.8% | 25.3% | 4.8% |
| Dysesthesia | 5.1% | 12.3% | 12.5% | 0.9% |
| Discontinuation due to adverse events | 4.1% | 6.9% | 11.3% | 4.9% |
TRIUMPH-4 had higher 12 mg discontinuation in the knee osteoarthritis population, 18.2%, and a higher dysesthesia rate, 20.9%. TRANSCEND-T2D-1 had lower discontinuation rates, 2.2% to 5.1%, over 40 weeks in adults with type 2 diabetes.
The practical read is mixed. Retatrutide produced the strongest weight-loss and complication signals in the class, but tolerability is not a footnote. The 4 mg arm in TRIUMPH-1 still produced 19.0% mean weight loss with a discontinuation rate below placebo, while the 12 mg arm produced the largest efficacy signal with more GI burden and more discontinuation.
Heart Rate & Cardiovascular Safety
Retatrutide causes a dose-dependent increase in resting heart rate. This is a known consequence of glucagon receptor agonism, the same mechanism that makes retatrutide uniquely powerful for fat burning also has direct effects on cardiac function. Understanding this signal is important for clinical decision-making.
Heart Rate Increase by Dose
| Dose | Avg. HR Increase at Peak (Week 24) |
|---|---|
| 4 mg (low) | +2 to +4 bpm |
| 12 mg (highest) | +~6.7 bpm |
| Semaglutide (reference) | +2 to +3 bpm |
| Tirzepatide (reference) | +2 to +4 bpm |
Why the Increase Happens
Glucagon receptor activation on cardiac cells triggers a cAMP-mediated pathway (via adenylyl cyclase and protein kinase A) that produces both chronotropic effects (faster rate) and inotropic effects (stronger contractions). This pathway is distinct from the sympathetic nervous system, which means beta blockers are likely less effective at controlling retatrutide-induced heart rate elevation than they would be for other causes of tachycardia.
Temporal Pattern: Peak and Partial Recovery
Heart rate elevation is not static during treatment. Available Phase 2 data shows:
- Week 24: Peak heart rate elevation across all dose groups
- Weeks 36-48: Partial decline despite continued dosing, consistent with physiological adaptation
- The increase does not appear to be permanent; it diminishes over time even without dose reduction
Serious Cardiovascular Events
Important caveat: Phase 2 trials excluded participants with significant pre-existing cardiovascular disease. This limits the applicability of these reassuring figures to higher-risk populations. The dedicated cardiovascular outcomes trial, TRIUMPH-Outcomes, is designed to answer whether retatrutide reduces MACE (major adverse cardiovascular events). Results are not expected until 2027-2028.
Net Cardiovascular Picture
The modest heart rate elevation needs to be weighed against substantial cardiovascular risk factor improvements seen across trials:
- Systolic blood pressure: down ~14 mmHg at the 12 mg dose (TRIUMPH-4)
- Non-HDL cholesterol: significantly reduced (TRANSCEND-T2D-1 and Phase 2)
- Triglycerides: significantly reduced across trials
- High-sensitivity CRP: decreased (anti-inflammatory signal)
- Dramatic reduction in liver fat (relevant for cardiometabolic risk)
For most patients without pre-existing cardiac disease, the net cardiometabolic effect of retatrutide appears favorable. A +5-7 bpm heart rate increase is within the range of normal daily variation (standing from sitting raises HR by 10-20 bpm) and is substantially offset by the blood pressure and lipid improvements.
Retatrutide vs. Tirzepatide vs. Semaglutide
Note: comparisons are across separate trials, not head-to-head studies. Individual results will vary.
| Retatrutide | Tirzepatide | Semaglutide | |
|---|---|---|---|
| Mechanism | GLP-1 + GIP + Glucagon | GLP-1 + GIP | GLP-1 only |
| Avg. Weight Loss | 28.7% (Phase 3) | 22.5% | 15% |
| Avg. Pounds Lost | 71.2 lbs | ~56 lbs | ~37 lbs |
| FDA Approved | ❌ Phase 3 | ✅ Yes | ✅ Yes |
| Brand Names | None yet | Mounjaro, Zepbound | Ozempic, Wegovy |
| Unique Benefit | Fat burning + energy expenditure | Dual pathway | Longest track record |
| Weight Plateau | Not observed at 48 wks | ~6–9 months | ~6 months |
| Liver Fat Reduction | Dramatic | Moderate | Some |
| Manufacturer | Eli Lilly | Eli Lilly | Novo Nordisk |
Frequently Asked Questions
When will retatrutide be available?
The earliest realistic timeline for FDA approval is late 2027 or 2028, assuming the remaining Phase 3 trials are positive and Eli Lilly files promptly. Seven more TRIUMPH trials are expected to report by end of 2026.
Is retatrutide better than tirzepatide?
Based on cross-trial comparisons, retatrutide has produced larger topline weight loss, 28.3% in TRIUMPH-1 vs. 22.5% for tirzepatide in SURMOUNT-1. However, there is no direct head-to-head comparison yet. Retatrutide also has a less established safety profile and a dysesthesia signal.
What is dysesthesia?
Dysesthesia is an abnormal sensation, including tingling, burning, or unusual perception of touch. It was reported in 5.1% to 12.5% of retatrutide-treated participants in TRIUMPH-1, compared with 0.9% on placebo. TRIUMPH-4 reported a higher 20.9% rate on 12 mg in the knee osteoarthritis population.
Can I buy retatrutide now?
Retatrutide is not FDA-approved and cannot be prescribed. Research peptide vendors sell it labeled 'for research use only,' but this carries significant risk: no quality assurance, no medical oversight, uncertain purity, and no lawful human-use product. We strongly advise against this and recommend waiting for an approved version.
Are real-world retatrutide reports reliable?
Not yet. Social posts, Reddit updates, and progress photos are anecdotes, not real-world evidence. They rarely verify the compound, dose, concentration, adverse events, medical history, or whether other medications were involved.
Should I wait for retatrutide instead of starting treatment now?
Usually not if you have a clear medical indication today. Semaglutide and tirzepatide are FDA-approved now, while retatrutide is still years away from routine prescribing. A clinician can help weigh current approved options against the uncertainty of waiting.
Will retatrutide replace tirzepatide?
Possibly for some patients. Eli Lilly makes both drugs and will likely position retatrutide for patients who need more aggressive weight loss than tirzepatide provides. The two may serve different market segments.
What about the higher side effect rates?
Retatrutide's GI side effects increase with dose. In TRIUMPH-1, nausea reached 42.4%, vomiting 25.3%, and discontinuation due to adverse events 11.3% on 12 mg, compared with 14.8%, 4.8%, and 4.9% on placebo. TRIUMPH-4 showed higher discontinuation in a knee osteoarthritis population.
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The Bottom Line
Retatrutide is the most powerful weight loss compound ever tested in large-scale clinical trials. The Phase 3 numbers are remarkable: 28.7% average weight loss, 71.2 lbs lost, with ongoing weight reduction at 68 weeks and no plateau in sight.
But it comes with important caveats. The safety profile needs more scrutiny. The dysesthesia signal is new and concerning at 20.9% incidence, and GI side effect rates are meaningfully higher than its predecessors. It remains years away from FDA approval, and the long-term consequences of such dramatic, rapid weight loss are still being studied.
For now, retatrutide represents the frontier of what's possible with obesity pharmacotherapy. If you need a treatment option today, semaglutide and tirzepatide are your FDA-approved options. If the TRIUMPH program continues to deliver, retatrutide may rewrite the playbook entirely. That conversation is for 2027 at the earliest.
Maintenance Dosing: After the Escalation Phase
A distinctive feature of retatrutide in Phase 3 data is that weight loss did not plateau during the 68-week escalation period, unlike semaglutide and tirzepatide, which typically plateau around 6–9 months. This raises important questions about long-term maintenance dosing that won't be fully answered until post-approval studies are completed.
Based on Phase 2 and the TRIUMPH-4 data available, the anticipated maintenance framework looks like this: after reaching the target dose (9 mg or 12 mg), patients are expected to remain on that dose indefinitely to maintain weight loss, consistent with the chronic treatment model established by semaglutide. Early discontinuation studies (analogous to STEP 4 for semaglutide) are part of the TRIUMPH program to characterize weight regain patterns after stopping.
One unresolved question is whether patients who achieve very high weight loss (30%+ body weight) can step down to a lower maintenance dose. This is being studied, but no data is available yet. Given that weight loss curves in TRIUMPH-4 had not plateaued at 68 weeks, some researchers have speculated that longer treatment durations may be required to reach a true maintenance equilibrium, and that the eventual maintenance dose may differ from the escalation endpoint.
Key open question
Unlike semaglutide and tirzepatide, which have well-characterized discontinuation data, retatrutide's maintenance and discontinuation profile is still being established through ongoing TRIUMPH trials. Expect more clarity as TRIUMPH-3 (maintenance population) reports in 2026.
Testosterone & Hormonal Effects
Emerging data from retatrutide trials suggests it may have a different hormonal impact profile compared to semaglutide and tirzepatide, driven specifically by its glucagon receptor activity, which the other approved drugs lack.
In men with obesity, significant weight loss from any cause tends to increase testosterone, because adipose tissue converts testosterone to estrogen, and losing fat reduces that conversion. Both semaglutide and tirzepatide show this effect. However, preliminary observations from retatrutide trials suggest the magnitude of testosterone recovery may be larger than weight loss alone would predict, possibly because glucagon receptor activation has independent effects on the hypothalamic-pituitary-gonadal (HPG) axis.
This is still emerging and preliminary. The hormonal data from TRIUMPH trials has not yet been fully published. Glucagon receptor signaling is known to interact with hepatic metabolism and adrenal function, and some researchers hypothesize that the glucagon component of retatrutide may have downstream effects on cortisol and sex hormone binding globulin (SHBG) that differ from pure GLP-1 agonists. For women, the implications for sex hormone levels, including in the context of PCOS, which is frequently comorbid with obesity, are also under investigation.
Availability
Retatrutide is currently in Phase 3 clinical trials and is not yet available through telehealth providers. We will update this guide when it becomes commercially available.
Sources
- 1.Jastreboff AM, et al. “Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial.” N Engl J Med. 2023;389(6):514–526.
- 2.Sanyal AJ, et al. “Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease.” Nat Med. 2024;30:2024–2033.
- 3.Eli Lilly. “Lilly's triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial.” Press release, December 11, 2025.
- 4.Eli Lilly. “Lilly's triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial.” Press release, May 21, 2026. (TRIUMPH-1 top-line results.)
- 5.ClinicalTrials.gov. NCT05929066: TRIUMPH-1 (A Study of Retatrutide in Participants Who Have Obesity or Overweight).
- 6.Rosenstock J, et al. “Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-comparator-controlled, parallel-group, phase 2 trial.” Lancet. 2023;402(10401):529–544.
- 7.ClinicalTrials.gov. NCT05931367: TRIUMPH-4.
- 8.“Retatrutide for the treatment of obesity, obstructive sleep apnea and knee osteoarthritis: Rationale and design of the TRIUMPH registrational clinical trials.” Diabetes Obes Metab. 2025.
- 9.Eli Lilly. “Lilly's triple agonist, retatrutide, demonstrated significant reductions in A1C and weight in first Phase 3 trial for treatment of type 2 diabetes.” Press release, March 19, 2026. (TRANSCEND-T2D-1 top-line results.)
- 10.ClinicalTrials.gov. NCT05929079: TRANSCEND-T2D-1 (A Study of Retatrutide in Participants With Type 2 Diabetes Mellitus).
- 11.Eli Lilly. “Lilly's triple agonist, retatrutide, drove substantial improvements in weight, A1C, knee osteoarthritis pain, and obstructive sleep apnea, demonstrating its remarkable potential to treat obesity and its complications.” Press release, June 6, 2026. (ADA 2026 TRIUMPH-1 and TRANSCEND-T2D-1 additional results.)
- 12.Bajaj HS, et al. “Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial.” Lancet. Published online June 6, 2026.
- 13.Jastreboff AM, et al. Retatrutide Phase 2 cardiovascular and heart rate data. N Engl J Med. 2023. (Heart rate subsection: peak +6.7 bpm at week 24, partial decline at weeks 36-48; arrhythmia signals 4-14% vs 2-3% placebo.)
- 14.FDA. “FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss.” FDA.gov. Updated 2026. Includes FDA position on retatrutide and cagrilintide compounding.
- 15.FDA warning letters to GLP-1 Solution, GenLabMeds, Amazing Meds, and Gram Peptides, 2025-2026. FDA enforcement examples for unapproved GLP-1 and retatrutide products.