Compound comparison
Retatrutide vs. Tirzepatide: What the Trials Actually Found
Retatrutide now has published phase 3 obesity results, but setting them beside tirzepatide’s results is not a head-to-head comparison. The studies enrolled different people, followed them for different periods and used their own analysis methods. Tirzepatide has approved prescription products; retatrutide remains investigational. The direct-comparison TRIUMPH-5 registry had no posted results when checked October 13, 2026.
Retatrutide
Research use onlyTriple agonist: GIP, GLP-1, and glucagon receptors.
Evidence strength: Randomized trials. Randomized controlled trials in humans, at scale.
Sold for laboratory use. Not a legal medicine for people.
Tirzepatide
FDA-approvedDual agonist: GIP and GLP-1 receptors.
Evidence strength: Randomized trials. Randomized controlled trials in humans, at scale.
Approved for this use and available by prescription.
This is not a head-to-head trial
These are separate trials with placebo controls, not a head-to-head result. Differences in participants, duration and analysis prevent their percentages from establishing which medicine works better in comparable patients.
What each trial reported
Every row is its own trial. Duration, sample size, and phase are shown next to every result on purpose — without them, a result is not a fact you can compare to anything.
| Compound | Trial | Population | Result | Duration | n | Phase | Status |
|---|---|---|---|---|---|---|---|
| Retatrutide | — | Adults with obesity, no diabetes | −24.2% at 12 mg · placebo −2.1% | 48 wks | 338 | phase 2 | Research use only |
| Retatrutide | TRANSCEND-T2D-1 | Adults with type 2 diabetes | −15.3% at 12 mg · placebo −2.6% | 40 wks | 537 | phase 3 | Research use only |
| Tirzepatide | SURMOUNT-1 | Adults with obesity, no diabetes | −20.9% at 15 mg · placebo −3.1% | 72 wks | 2,539 | phase 3 | FDA-approved |
| Retatrutide | TRIUMPH-1 | Adults with obesity, without diabetes; treatment-regimen analysis | −25.0% at 12 mg · placebo −3.9% | 80 wks | 2,339 | phase 3 | Research use only |
| Retatrutide | TRIUMPH-2 | Adults with overweight or obesity and type 2 diabetes; treatment-regimen analysis | −18.8% at 12 mg · placebo −5.1% | 80 wks | 1,152 | phase 3 | Research use only |
Why separate trial averages do not establish a winner
A trial result belongs to its study population, dose, follow-up period and statistical analysis. Placebo groups also differ. Subtracting one medicine’s headline percentage from another’s cannot reproduce a randomized comparison.
Retatrutide now has phase 3 obesity results
The earlier phase 2 obesity study randomized 338 adults and reported a 24.2% mean weight reduction in its 12 mg group at 48 weeks, versus 2.1% on placebo 1. That is a dose-group average, not an individual maximum.
TRANSCEND-T2D-1 subsequently reported 15.3% at 40 weeks on 12 mg versus 2.6% on placebo in 537 adults with type 2 diabetes. Its primary endpoint was blood-sugar control, with weight as a secondary endpoint 2. That shorter diabetes trial did not invalidate the earlier obesity result; it answered a different question.
The September 2026 publications add two larger studies. TRIUMPH-1 studied obesity without diabetes; TRIUMPH-2 studied overweight or obesity with type 2 diabetes. Both followed participants for 80 weeks. Their treatment-regimen results are shown above 45. Older descriptions of retatrutide as having only a phase 2 obesity result are therefore out of date.
Tirzepatide’s established obesity trial
SURMOUNT-1 randomized 2,539 adults with obesity or overweight and a weight-related complication, without diabetes. The 15 mg group had a 20.9% mean reduction at 72 weeks versus 3.1% on placebo 3. That result remains useful, but it should not be treated as a control group for a different retatrutide trial.
What the direct comparison can answer
[TRIUMPH-5](https://clinicaltrials.gov/study/NCT06662383) compares retatrutide with tirzepatide within one study. Its registry record, checked October 13, 2026, lists an estimated 800 participants, active-not-recruiting status and estimated December 2026 completion, with no posted results. A projected completion date is not a promised publication date.
Availability is a separate decision
Tirzepatide has FDA-approved prescription products. Retatrutide does not: FDA states that it is not a component of an approved drug and cannot be used in compounding under federal law 6. Clinical trials and narrowly defined physician-requested expanded access are different from ordinary commercial prescribing.
A newer trial publication can strengthen the evidence without establishing an approved product, routine dose, retail price or supply chain. For the fuller evidence and safety context, see our retatrutide guide and tirzepatide guide.
Frequently asked questions
Has retatrutide been tested head-to-head against tirzepatide?
TRIUMPH-5 is the registered direct comparison. Its registry had no posted results when checked October 13, 2026, so the separate trial averages on this page do not establish a winner.
Does retatrutide have phase 3 obesity results?
Yes. TRIUMPH-1 and TRIUMPH-2 were published in September 2026 and followed their different populations for 80 weeks. Neither compared retatrutide directly with tirzepatide.
Can you get an ordinary retatrutide prescription?
There is no FDA-approved retatrutide product, and FDA states it cannot be used in compounding under federal law. Clinical trials and physician-requested expanded access have separate rules and are not retail prescribing routes.
References
- Jastreboff AM, Kaplan LM, Frías JP, et al. (2023). Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/37366315/
- Bajaj HS, Welch M, Shah P, et al. (2026). 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. The Lancet. https://pubmed.ncbi.nlm.nih.gov/42250575/
- Jastreboff AM, Aronne LJ, Ahmad NN, et al. (2022). Tirzepatide Once Weekly for the Treatment of Obesity. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/35658024/
- Jastreboff AM, Kaplan LM, Davies MJ, et al. (2026). Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity. New England Journal of Medicine. https://pubmed.ncbi.nlm.nih.gov/42814954/
- Bellido V, le Roux CW, Ekinci EI, et al. (2026). Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. The Lancet. https://pubmed.ncbi.nlm.nih.gov/42810372/
- US Food and Drug Administration (2026). FDA’s Concerns with Unapproved GLP-1 Drugs Used for Weight Loss. FDA — accessed October 13, 2026. https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
Medical disclaimer: This content is for general educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a licensed healthcare professional before starting, stopping, or changing any treatment.