Research Guide · Updated July 2026

Retatrutide vs Tirzepatide: UK Research Comparison

Retatrutide and Tirzepatide are the two most discussed incretin research peptides in the UK laboratory community. Both target GLP-1 signalling, but their receptor profiles — and the trial data behind them — are meaningfully different. This guide compares the two side by side for research reference.

Receptor profile at a glance

Tirzepatide is a dual agonist: it activates GLP-1 and GIP receptors. It is the molecule marketed as Mounjaro / Zepbound and has an extensive Phase 3 dataset (SURPASS, SURMOUNT).

Retatrutide is a triple agonist: GLP-1, GIP and glucagon receptors. The added glucagon component increases energy expenditure in preclinical models. Phase 2 data (TRIUMPH-1, published NEJM 2023) reported ~24% mean body-weight reduction at 48 weeks in the highest-dose cohort — the largest effect size published for any incretin candidate to date.

Published research data (for reference)

Tirzepatide SURMOUNT-1 (NEJM 2022): 15–20.9% mean body-weight reduction at 72 weeks across doses 5–15 mg.

Retatrutide TRIUMPH-1 (NEJM 2023): 17.5% at 8 mg and 24.2% at 12 mg mean body-weight reduction at 48 weeks. Phase 3 (TRIUMPH-4) is ongoing.

Both molecules produced dose-dependent GI adverse events in trials; retatrutide additionally produced modest increases in resting heart rate consistent with glucagon-receptor activity.

Handling and reconstitution

Both peptides ship lyophilised and are reconstituted with bacteriostatic water. Typical research prep: 2 mL BAC water into a 10 mg vial gives 5 mg/mL. See our reconstitution calculator for exact volumes at any concentration.

Store lyophilised vials at 2–8 °C; reconstituted vials stable ~28 days refrigerated. Do not shake — swirl gently to dissolve.

Sourcing in the UK

Both Retatrutide and Tirzepatide are available from Professor Peptide in multiple vial sizes with a Certificate of Analysis for every batch. UK-based dispatch means no customs risk and next-day delivery on orders placed before 2 pm.

For a research comparison study, ordering matched vial sizes of each (e.g. 10 mg × 10 mg) with the same batch date allows cleaner methodology.

Frequently Asked Questions

Is retatrutide stronger than tirzepatide?+

In published Phase 2/3 data, retatrutide has produced a larger mean body-weight reduction than tirzepatide at comparable time points, but head-to-head trials have not yet been published.

Can I buy retatrutide and tirzepatide in the UK?+

Yes, both are legal to purchase in the UK for laboratory research use only. They are not licensed for human use unless prescribed as an approved medicine.

Do you provide a Certificate of Analysis?+

Yes — every batch of retatrutide and tirzepatide from Professor Peptide ships with a downloadable CoA showing purity (HPLC) and identity (mass spec).

Which vial size should I choose for a comparison study?+

Matching sizes (e.g. 10 mg vs 10 mg) simplifies dose calculations. For longer studies, 15 mg or 20 mg vials reduce the number of reconstitutions required.