Is Retatrutide the same as Mounjaro?

No. Mounjaro is Eli Lilly's brand name for Tirzepatide, a dual GLP-1 + GIP agonist. Retatrutide is a separate Lilly compound and is a triple agonist (GLP-1 + GIP + Glucagon).

Is Retatrutide stronger than Mounjaro?

In published trials, Retatrutide's Phase 2 top-dose weight-loss numbers exceed Tirzepatide's Phase 3 top-dose numbers, but head-to-head trials have not yet been published.

Can I get Retatrutide on the NHS like Mounjaro?

No. Retatrutide is not licensed by the MHRA and is not prescribable on the NHS. It is only available as a research chemical.

Is Retatrutide legal in the UK?

Yes, for laboratory research use only. It is not licensed for human use.

Retatrutide vs Mounjaro — Is Retatrutide Better? (UK 2026)

Retatrutide vs Mounjaro (Tirzepatide) — a UK 2026 comparison of receptor targets, published trial weight-loss data, availability, price and how researchers choose between them.

For laboratory research and in vitro use only. Not for human or veterinary use. Mounjaro is a registered trademark of Eli Lilly; this article compares the underlying compounds, not brand marketing.

"Mounjaro" is Eli Lilly's brand name for Tirzepatide — a licensed UK medicine. Retatrutide is Lilly's next-generation compound, still in Phase 3 trials and not licensed for human use in the UK. Both come out of the same pipeline; they are not the same molecule. Here's how they actually differ.

Mechanism — dual vs triple agonist

Mounjaro / Tirzepatide — dual agonist: GLP-1 + GIP.
Retatrutide — triple agonist: GLP-1 + GIP + Glucagon.

The added glucagon receptor activity is the whole point of Reta. Glucagon receptor agonism increases energy expenditure — where Tirzepatide primarily reduces energy intake, Retatrutide affects both sides of the equation.

Published trial data

In Retatrutide's Phase 2 obesity trial (NEJM, 2023), the top dose (12mg weekly) produced a mean body-weight reduction of around ~24% at 48 weeks. Tirzepatide's SURMOUNT-1 trial (NEJM, 2022) reported around ~20.9% at 72 weeks at 15mg. Direct head-to-head trials have not yet been published — but Reta's shorter-horizon numbers already exceed Tirz's longer-horizon numbers.

UK availability

Mounjaro — licensed by the MHRA, available on prescription. Can be reached through UK pharmacies and some NHS pathways under NICE guidance.
Retatrutide — not licensed, not on the NHS, not in pharmacies. UK researchers currently access it as a lab-grade research peptide from specialist suppliers such as Peptides UK 4U.

Price

Mounjaro pharmacy pricing in the UK typically runs £150–£220 per pen. Retatrutide as a lab-grade research compound is priced per vial size (20mg / 30mg / 40mg) — see live pricing on the Retatrutide product page. £/mg is broadly favourable to Reta, but the two are not interchangeable products.

Format

Mounjaro ships as a pre-filled disposable pen. Retatrutide ships as a lyophilised vial for reconstitution — or, at Peptides UK 4U, optionally as a pre-filled UK-prepared Retatrutide Quick Pen in 20mg / 30mg / 40mg.

"Is Retatrutide better than Mounjaro?"

On the trial numbers so far, Retatrutide's efficacy is stronger — but Mounjaro is licensed, prescribable and quality-controlled through the pharmaceutical supply chain. The two answer different questions. If your work needs a research compound with the most current mechanism of action, Reta is the answer. If your endpoint is a licensed UK medicine, that is Mounjaro / Tirzepatide.