Retatrutide
GLP-1 / GIP / glucagon agonist
- Injection
- Oral
- Nasal spray
- Suppository
- Gel or cream
Injection — once weekly, inside a trial.
No provider we've verified carries Retatrutide yet
Retatrutide is an investigational synthetic peptide from Eli Lilly, coded LY3437943, and it activates three metabolic receptors at once: GLP-1, GIP, and glucagon. There is no brand name because there is no approved product.
The class it belongs to is defined by how many receptors a molecule reaches. Semaglutide hits one. Tirzepatide hits two. Retatrutide hits three, and the third one is the interesting part. GLP-1 activation does the heavy lifting for the whole class — glucose-dependent insulin secretion, slowed gastric emptying, and the satiety signaling that makes people eat less. GIP adds insulin secretion and changes how fat tissue handles energy. Glucagon-receptor agonism sounds like the wrong idea in a metabolic drug, because glucagon raises blood sugar — but chronic low-grade activation also pushes resting energy expenditure up and strips fat out of the liver, and in this molecule the hyperglycaemic effect is more than offset by the other two receptors.
Output up, intake down — that combination is what predicted an effect size no obesity drug had reported before, and it is why the trial curves had not flattened when the study ended.
The numbers are the reason anyone has heard of it. In the Phase 2 obesity trial, 338 adults over 48 weeks, the 12 mg arm reached about 24.2% mean body-weight reduction against 2.1% on placebo, and a substantial share of that group crossed 30% — territory that used to belong to bariatric surgery. Lilly’s Phase 3 obesity topline reports more, with a trial extension reaching roughly 30% at two years on the top maintained dose. For the trial-by-trial record, the receptor pharmacology and every citation behind those figures, read the deep-dive on PeptideWellness.
Who it's for (or who should avoid)
What it's aimed at
Nobody is prescribed retatrutide, so the honest version of this section is who the trials enrolled:
- Adults with obesity — BMI 30 or above, or 27 to 30 with at least one weight-related condition; mean baseline BMI in Phase 2 sat around 37, and TRIUMPH-1 went heavier still
- Adults with type 2 diabetes — a separate program, TRANSCEND, whose first readout took medication-naive patients with a mean diabetes duration of about two and a half years
- Obesity with knee osteoarthritis — TRIUMPH-4 studied 445 adults and reported knee-pain reduction alongside weight loss
- Obesity with obstructive sleep apnoea — covered by basket sub-studies within the TRIUMPH program
Recruitment for the largest studies is now substantially closed, though extensions and sub-studies continue. ClinicalTrials.gov is the place to check, and it is the only place where access is a real question rather than a marketing one.
Who should avoid it
- Anyone with a personal or family history of medullary thyroid carcinoma or MEN type 2 — a class contraindication, not a caution
- People with a history of pancreatitis, or with low eGFR
- Anyone pregnant, breastfeeding or planning a pregnancy — no controlled human data
- Adolescents — not enrolled, so not known
- Anyone considering a vial bought online, which is the group this page is really for: what is sold as retatrutide has no verified potency, no sterility certification and no identity assurance, and the trial figures above were produced by a supervised protocol with monitoring, not by a syringe and a forum thread
Route, dose and course
In trials, retatrutide is a once-weekly subcutaneous injection. The fatty-diacid tail that stretches its half-life to roughly six days is the same pharmacokinetic trick that bought semaglutide and tirzepatide their weekly schedules.
The protocol the trials used:
- Doses studied: 1, 4, 8 and 12 mg once weekly in Phase 2, with stepwise titration into the higher arms
- Titration: upward in steps, which is where the GI symptoms concentrate — starting at a therapeutic dose is not how any of these trials were run
- Monitoring: supervised, with dropout and adverse events tracked; heart rate and glycaemic markers followed throughout
- Where: an active Lilly trial site, because there is no pharmacy route — it is not approved, so it cannot be dispensed, and it is not on the shortage list, so it cannot be compounded
There is nothing to reconstitute at home and no prescriber who can write for it. A clinician’s role here is the conversation about what you are actually considering, and about the drugs that are available now.
The usual arc
Read this first. These are trial figures, not a prescription plan — every one of them comes from a supervised study with titration, monitoring and dropout tracking. Nobody outside a trial is on this schedule, and the numbers should not be read as what a gray-market vial would do.
Retatrutide’s arc is a trial arc, and that is the only honest way to read it: titration first, the largest changes at the higher maintained doses months in, and a curve that had not finished falling when the study stopped.
- WEEK 1–4Titration, and the GI taxTrials start low and step up. Nausea, vomiting, diarrhoea and constipation cluster here, are dose-dependent, and are mostly mild to moderate. Heart rate rises a few beats per minute over the following months before settling.
- WEEK 24About 17.5% on the top doseThe Phase 2 midpoint on 12 mg weekly. HbA1c, systolic blood pressure, triglycerides and liver fat all moved in the expected direction alongside the weight.
- WEEK 48About 24.2%, still fallingThe Phase 2 endpoint — and the line that mattered to the field was not the number but its slope: the curve had not plateaued, so 48 weeks was a floor rather than a ceiling. Phase 3 has since reported further loss into a second year.
No provider we've verified carries Retatrutide yet
That is the honest answer, and it is not the same as "you can't have it". None of the licensed telehealth providers we track publishes Retatrutide, so there is no price to quote and no intake to send you to. Whether that changes depends on federal action rather than on us — which is why the next box exists rather than a button that goes nowhere.
Tell me when someone carries it
Questions we get about Retatrutide
Is retatrutide FDA-approved?
No. It has no FDA approval and no approved label, and it is not approved by the EMA or the MHRA either. It is investigational, in Phase 3, and as of mid-2026 no New Drug Application has been publicly confirmed as submitted. Analyst timelines pointing at 2027 or 2028 are projections — there is no PDUFA date because there is no application on the public record.
Can I buy retatrutide legally?
No. Enrolling in an Eli Lilly trial is the only lawful route in the US. It cannot be compounded: the 503A and 503B pathways cover approved drugs and substances on specific FDA lists, and an unapproved investigational molecule is neither. Anything sold as retatrutide by a peptide vendor or a compounding pharmacy is outside that framework, and the practical problem is not only legal — potency, sterility and identity are all unverified in that market.
See what licensed providers actually carry →How does it compare to semaglutide and tirzepatide?
Across separate trials — not head-to-head — retatrutide's Phase 2 produced about 24% mean weight loss at 48 weeks, tirzepatide about 20.9% at 72 weeks in SURMOUNT-1, and semaglutide about 14.9% at 68 weeks in STEP-1. The populations overlap but are not identical, so the comparison is suggestive rather than settled. The mechanistic difference is real: the third receptor adds a push on energy expenditure that the other two do not have.
What is the safety signal people mention?
Dysesthesia — tingling or altered skin sensation. It was not prominent in Phase 2 and appeared at Phase 3 scale: 20.9% of participants on 12 mg and 8.8% on 9 mg in the TRIUMPH-4 topline, against 0.7% on placebo, described by the sponsor as generally mild and rarely a reason to stop. Those are company-reported figures awaiting peer review. Pharmacovigilance data show similar signals across the GLP-1 class, so it is not unique to this molecule — what looks distinctive is the dose-dependence and the size of the gap over placebo.
Will the weight come back if I stop?
There is no published retatrutide discontinuation data, which makes this the biggest open practical question about it. What the class shows is substantial regain after stopping, and whether the glucagon component changes that is an empirical question nobody has answered yet. The longest published exposure runs to about two years.
We publish no medical reviewer by design. Every claim on this page traces to a source we hold on file, and the reviewed write-up with those citations lives on our hub. Read the full research on PeptideWellness ↗
Fuel your protocol with
the latest research + reviews
Independent updates on peptide therapy, breaking news from compounding pharmacies, and exclusive guides — straight to your inbox.
