Quick answer
Retatrutide is Eli Lilly's triple GLP-1/GIP/glucagon ('triple-G') weekly injection. As of June 2026 it is not MHRA-approved and not available from any GPhC-registered UK provider. Trial data show high weight loss at the top dose, but UK approval is not expected in the near term. Speak to your prescriber about approved options.
Retatrutide UK: what it is, what the trials show, and when it might arrive
Retatrutide is a triple-receptor agonist drug from Eli Lilly — the same company behind Mounjaro (tirzepatide). Where Mounjaro activates two receptors (GLP-1 and GIP), retatrutide activates three: GLP-1, GIP, and glucagon. This triple mechanism is why it is sometimes called a “triple G” agonist, and why early trial results attracted significant attention from obesity medicine researchers.
Status as of June 2026: Retatrutide has not received MHRA approval for use in the UK. It is not available from any GPhC-registered UK pharmacy or online clinic. Any UK website currently selling it is not operating as a legitimate regulated pharmacy.
How retatrutide works — the triple mechanism explained
Most GLP-1 drugs work by mimicking the hormone GLP-1, which is released after eating and signals fullness, slows gastric emptying and stimulates insulin release. Mounjaro added GIP (glucose-dependent insulinotropic polypeptide) activation, which appeared to significantly improve weight loss outcomes compared to GLP-1 alone — the SURMOUNT trials confirmed this.
Retatrutide adds a third receptor target: the glucagon receptor. Glucagon is a hormone that raises blood sugar and increases energy expenditure (calorie burning). At first this sounds counterproductive for weight management, but at the doses used in the retatrutide trials, the glucagon activation appeared to increase energy expenditure and drive additional fat loss, particularly visceral fat. The combination — reduce appetite (GLP-1/GIP) while increasing calorie burning (glucagon) — is the theoretical basis for retatrutide’s strong trial results.
What the TRIUMPH phase 3 trial programme shows
Eli Lilly’s phase 3 programme for retatrutide (in obesity) is called TRIUMPH. Phase 2 results, published in The New England Journal of Medicine in 2023, showed:
- Up to 24.2% body weight reduction at 48 weeks at the highest dose (12mg weekly injection)
- Significant reductions in waist circumference and cardiometabolic markers
- Side effect profile broadly consistent with other GLP-1 drugs: nausea, vomiting, diarrhoea — predominantly mild to moderate and occurring early in treatment
These are phase 2 results. Phase 3 data are required for regulatory approval. Phase 3 TRIUMPH trial results were reported in 2025. Full peer-reviewed phase 3 publications are the authoritative source — media summaries of trial results vary significantly in accuracy.
Important: retatrutide is an injection, not a tablet
This is a critical point for our audience. Retatrutide is a weekly subcutaneous injection — the same administration route as Wegovy injection and Mounjaro. It is not an oral tablet. If you are specifically looking for an oral weight loss tablet that does not require injections, retatrutide is not it.
For oral options, see our guides to the oral GLP-1 tablets currently available or in development in the UK.
How does retatrutide compare to the Wegovy tablet?
They are entirely different products serving different needs:
| Factor | Wegovy tablet | Retatrutide |
|---|---|---|
| Drug type | Oral peptide (semaglutide) | Weekly injection |
| Receptor targets | GLP-1 only | GLP-1, GIP, glucagon |
| Manufacturer | Novo Nordisk | Eli Lilly |
| UK approval status | Approved, pre-order live | Not yet MHRA-approved |
| Administration | Daily oral tablet | Weekly injection |
| Phase 2 weight loss | ~15% at 68 weeks (OASIS) | ~24% at 48 weeks (phase 2) |
See our full retatrutide vs Wegovy tablet comparison.
The “research peptide” gray market — a warning
A significant proportion of searches for retatrutide in the UK are from people looking to buy it as a “research peptide” or “research chemical” from grey-market online suppliers. We do not list, link to or endorse these sources. Retatrutide obtained outside of a licensed medical supply chain:
- Is not subject to pharmaceutical quality controls
- May be mislabelled, contaminated or dosed inaccurately
- Is not prescribed or supervised by a clinician
- Does not constitute legitimate medical treatment
If you are looking for a supervised, clinically appropriate weight management treatment now, the Wegovy tablet is available from regulated UK providers. See our live provider tracker.
When will retatrutide be approved in the UK?
See our dedicated retatrutide UK availability tracker for a full regulatory timeline breakdown. The short version: MHRA approval depends on Eli Lilly submitting a Marketing Authorisation Application. As of June 2026, no confirmed UK submission or approval date has been published.
Get notified when retatrutide reaches the UK
We track all pipeline weight loss drugs including retatrutide as part of our broader drug intelligence coverage. Subscribe below for an alert when retatrutide receives MHRA approval or a UK launch date is confirmed.
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Frequently asked questions
What is retatrutide?
Retatrutide (LY3437943) is a triple GLP-1/GIP/glucagon receptor agonist injectable drug from Eli Lilly. Phase 2 trials showed up to 24% body weight reduction at 48 weeks. It is not yet approved by the MHRA or FDA for clinical use.
Is retatrutide available in the UK?
No. As of June 2026, retatrutide has not received MHRA approval. It is not available from any GPhC-registered UK pharmacy or online clinic.
Is retatrutide a tablet or injection?
Retatrutide is a weekly subcutaneous injection — not an oral tablet. For oral options currently available in the UK, see the oral GLP-1 tablet tracker.
How does retatrutide compare to Mounjaro?
Both are from Eli Lilly and both are weekly injections. Mounjaro (tirzepatide) targets GLP-1 and GIP receptors and is approved and available in the UK. Retatrutide adds glucagon receptor activation and showed stronger phase 2 weight loss results, but is not yet approved.
Can I buy retatrutide in the UK?
Not from any legitimate, GPhC-registered source. Gray-market research peptide sources exist but we do not link to or endorse them. These are unregulated, unsupervised and potentially dangerous.
Frequently asked questions
Is retatrutide available in the UK?
No. As of June 2026 retatrutide has no MHRA approval and is not supplied by any GPhC-registered UK pharmacy. 'Research peptide' sources are unregulated and unsafe.
How much weight loss does retatrutide cause?
Trials report high weight loss at the highest dose, with results varying by individual. Figures should be read in context — no UK-approved label exists yet. We will publish verified data as it is confirmed.
Is retatrutide a tablet or injection?
Retatrutide is a weekly subcutaneous injection, not a tablet. For an oral option available now, the Wegovy tablet starts at £64/month.
When will retatrutide be approved in the UK?
No confirmed date. Eli Lilly has not published a UK submission timeline. We alert subscribers on MHRA approval.