Comparison Guide
Retatrutide vs Semaglutide (Ozempic & Wegovy)triple agonist meets the original GLP-1.
Semaglutide acts on one receptor (GLP-1); Retatrutide acts on three (GLP-1, GIP and glucagon). In separate trials, Retatrutide reached ≈24% mean weight loss at 48 weeks versus ≈15% for Semaglutide at 68 weeks. Retatrutide is investigational and research-use-only; Semaglutide is MHRA-approved.
This page traces the jump from a single-receptor GLP-1 to a triple agonist: what the two added receptors (GIP and glucagon) actually do on top of the appetite and gastric-emptying effects that made Semaglutide — sold as Ozempic and Wegovy — the category benchmark, and how Retatrutide (LY3437943) builds on it.
At a glance
Retatrutide vs Semaglutide: key differences.
Receptor targets
Retatrutide
GLP-1 + GIP + Glucagon (triple)
Semaglutide
GLP-1 only
Peak weight loss
Retatrutide
≈24.2% at 48 wks · 12mg
Semaglutide
≈14.9% at 68 wks · 2.4mg
Regulatory status (UK)
Retatrutide
Investigational — research only
Semaglutide
MHRA approved (Wegovy, Ozempic)
Full comparison
Retatrutide vs Semaglutide: full spec sheet.
| Attribute | Retatrutide | Semaglutide |
|---|---|---|
| Drug class | GLP-1/GIP/Glucagon triple agonist | GLP-1 receptor agonist |
| Developer | Eli Lilly (LY3437943) | Novo Nordisk |
| UK brands | None — investigational | Ozempic, Wegovy, Rybelsus |
| Administration | Weekly subcutaneous pen | Weekly subcutaneous (or daily oral) |
| Max dose (studied) | 12 mg weekly | 2.4 mg weekly (Wegovy) |
| Weight loss (peak) | ≈24% (Phase 2, 48 wks) | ≈14.9% (STEP-1, 68 wks) |
| HbA1c reduction | ≈2.0% at 12 mg | ≈1.8% at 1 mg |
| Year of approval | Not yet (Phase 3 ongoing) | 2017 (Ozempic) · 2021 (Wegovy) |
| Mechanism advantage | Energy expenditure + appetite + hepatic fat | Appetite suppression + gastric emptying |
| Trial program | TRIUMPH | STEP / SUSTAIN |
Clinical evidence
Retatrutide vs Semaglutide trial weight-loss results.
Semaglutide (STEP-1, NEJM 2021) set the modern benchmark at ≈15% mean weight loss. Retatrutide Phase 2 (NEJM 2023) extended the headline number significantly — albeit at a shorter 48-week endpoint.
Retatrutide · NEJM 2023
−24.2%
mean body weight at 48 weeks · 12mg dose
- • 100% of high-dose participants lost ≥5%
- • 83% lost ≥15%
- • 26% lost ≥30%
Semaglutide · STEP-1
−14.9%
mean body weight at 68 weeks · 2.4mg dose
- • 86% lost ≥5%
- • 50% lost ≥15%
- • 32% lost ≥20%
Titration
Different molecules, similar 16-week ramp.
Retatrutide titration
- Weeks 1–4: 2 mg weekly
- Weeks 5–8: 4 mg weekly
- Weeks 9–12: 6 mg weekly
- Weeks 13–16: 8 mg weekly
- Weeks 17+: 10–12 mg weekly
Semaglutide (Wegovy) titration
- Weeks 1–4: 0.25 mg weekly
- Weeks 5–8: 0.5 mg weekly
- Weeks 9–12: 1.0 mg weekly
- Weeks 13–16: 1.7 mg weekly
- Weeks 17+: 2.4 mg weekly
Tolerability
Side-effect profile.
Both molecules carry the GLP-1 GI signature. Retatrutide adds glucagon-mediated effects (transient heart-rate rise) absent from Semaglutide. Semaglutide carries the longest real-world safety record of any GLP-1 to date.
Nausea
Most common · diminishes after weeks 4–8 in both
Diarrhoea / constipation
Dose-dependent · pronounced in titration
Decreased appetite
Expected pharmacological effect
Heart-rate (Retatrutide)
Modest transient increase observed in Phase 2
Long-term safety data
Semaglutide has 8+ years post-approval real-world data
Cautions & contraindications
Limitations & who this isn't for.
Semaglutide is an established, MHRA-approved GLP-1 with years of real-world data. Retatrutide is the opposite end of the maturity curve: an investigational triple agonist supplied for laboratory research only, not approved by the MHRA. Nothing here is medical advice, and the two added receptors bring cautions Semaglutide does not.
Not for human use
Retatrutide is not MHRA-approved. Research-grade pens are supplied for in-vitro laboratory use only, not for self-administration or treatment. Semaglutide (Wegovy, Ozempic) is the approved option.
Less safety data than Semaglutide
Semaglutide has years of post-approval real-world data; Retatrutide's evidence is limited to trials, with no long-term safety record. The newer molecule is the less-characterised one.
Added glucagon-driven effects
Unlike single-receptor Semaglutide, Retatrutide's glucagon agonism produced a transient heart-rate increase in Phase 2 — a class effect absent from the GLP-1-only comparator.
Dose-dependent GI effects
Nausea, vomiting, diarrhoea and constipation rise with dose and rapid titration across the GLP-1/GIP/glucagon class. Both molecules share this signature.
Who it would be inappropriate for
In any clinical context, GLP-1-class agonists are generally avoided with a personal/family history of medullary thyroid carcinoma or MEN 2, pancreatitis, or during pregnancy — decisions for a qualified clinician, not this page.
The verdict
Semaglutide proved the category. Retatrutide is the next chapter.
Body Pharm Retatrutide pens are supplied in the UK for laboratory research — 32mg and 64mg multi-dose pens, cold-chain shipped, with batch COA on request.
Common Questions
Retatrutide vs Semaglutide FAQ.
Is Retatrutide more effective than Semaglutide?
Phase 2 Retatrutide data reported ≈24% mean body weight reduction at 48 weeks at 12mg, vs ≈15% for Semaglutide at 2.4mg in STEP-1 over 68 weeks. These are cross-trial comparisons, not head-to-head.
Is Retatrutide the same as Ozempic?
No. Ozempic and Wegovy are brand names for Semaglutide, a single GLP-1 agonist made by Novo Nordisk. Retatrutide is a separate Eli Lilly molecule acting on three receptors (GLP-1, GIP and glucagon).
Why does Retatrutide work harder on weight loss?
The added glucagon receptor agonism is hypothesised to increase basal energy expenditure and accelerate hepatic fat reduction, on top of the appetite and gastric-emptying effects shared with Semaglutide.
Is Retatrutide approved in the UK?
Not yet. Retatrutide is investigational and supplied for in-vitro research only. Semaglutide (Wegovy, Ozempic) is MHRA approved.