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Comparison

Retatrutide vs Semaglutide vs Tirzepatide — comparison guide

How the three leading GLP-1 compounds compare on weight loss data, mechanism, availability and cost — and what the research shows about each.

Updated 5 Apr 2026
Reading time 10 min
🇦🇺 AU🇬🇧 UK🇨🇦 CA🇩🇪 DE🇺🇸 US
24.2%
Retatrutide Phase 2 weight loss (48 weeks)
21%
Tirzepatide Phase 3 weight loss (72 weeks)
15%
Semaglutide Phase 3 weight loss (68 weeks)

Three GLP-1 class compounds dominate the weight loss research landscape. Semaglutide (Ozempic/Wegovy) is the most widely prescribed. Tirzepatide (Mounjaro/Zepbound) added a second receptor target and improved on the data. Retatrutide goes further still — triple receptor agonism across GLP-1, GIP and glucagon.

💡 Plain English
In plain English — semaglutide targets one hunger hormone pathway. Tirzepatide targets two. Retatrutide targets three. More pathways means more levers being pulled simultaneously, which is why the weight loss data improves with each generation.

Mechanism comparison

Mechanism of action
CompoundReceptor targetsPhase weight lossApproval statusAvailability
Retatrutide strongest data GLP-1 + GIP + glucagon24.2% (Phase 2)Phase 3 trialsResearch only
Tirzepatide GLP-1 + GIP21% (Phase 3)TGA/FDA approvedPrescription
Semaglutide GLP-1 only15% (Phase 3)TGA/FDA approvedPrescription
🔬 Research finding
Retatrutide Phase 2 data (48 weeks at 12mg) showed 24.2% weight reduction. Phase 3 TRIUMPH trials are ongoing. Final Phase 3 data is expected by late 2025 / early 2026.

The compounds

Market availability

Availability differs significantly by compound and market. Semaglutide and tirzepatide are prescription medicines across all five markets. Retatrutide is unscheduled research compound available without a prescription for research purposes.

Market Legal status Avg price Vendors
🇦🇺Australia Legal for research A$89–120 / 5mg 4 verified View AU vendors →
🇬🇧United Kingdom Legal for research £64–89 / 5mg 3 verified View UK vendors →
🇨🇦Canada Legal for research CA$99–130 / 5mg 2 verified View CA vendors →
🇩🇪Deutschland Legal for research €74–99 / 5mg 2 verified View DE vendors →
🇺🇸United States Research only US$69–94 / 5mg 3 verified View US vendors →
Related stack
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References

1
Jastreboff AM et al. (2023). Triple hormone receptor agonist retatrutide for obesity. New England Journal of Medicine. Key finding: 24.2% mean weight reduction at 48 weeks, 12mg cohort
2
Jastreboff AM et al. (2022). Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine. Key finding: 20.9% mean weight reduction at 72 weeks
3
Wilding JPH et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine. Key finding: 14.9% mean weight reduction at 68 weeks