Retatrutide vs Semaglutide
A neutral, side-by-side comparison of two glp-1 & metabolic peptides — their mechanisms, dosing ranges, administration routes, side effects, and research evidence. For research and educational purposes only.
Retatrutide
Retatrutide (LY3437943) is Eli Lilly's investigational once-weekly triple agonist of the GIP, GLP-1, and glucagon receptors. Phase 2 data showed 24.2% mean weight loss at 48 weeks; the Phase 3 TRIUMPH program has since reported topline weight loss approaching 28–30% — among the largest reductions recorded for any obesity pharmacotherapy. It is not yet FDA-approved.
Full profileSemaglutide
Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist originally developed for type 2 diabetes management. It is FDA-approved under the brand names Ozempic (diabetes) and Wegovy (weight loss) and has become one of the most widely discussed peptides in mainstream health conversations.
Full profile| Retatrutide | Semaglutide | |
|---|---|---|
| Category | GLP-1 & Metabolic | GLP-1 & Metabolic |
| Also known as | LY3437943, Triple G, GIP/GLP-1/Glucagon Receptor Agonist | Ozempic, Wegovy, Rybelsus, GLP-1 agonist |
| Evidence | Investigational (in trials) | FDA-approved |
| Dosing range | 2mg–12mg mg, once weekly | 0.25mg–2.4mg mg, once weekly (injectable); once daily (oral Rybelsus) |
| Administration | Subcutaneous injection (weekly) | Subcutaneous injection (weekly — Ozempic/Wegovy), Oral tablet (daily — Rybelsus) |
| Key side effects | Nausea (most common, dose-dependent), Vomiting, Diarrhea, Constipation | Nausea (very common, especially during dose escalation), Vomiting, Diarrhea or constipation, Reduced appetite (intended effect) |
| Cited sources | 6 references | 4 references |
Key differences
- Evidence level differs: Retatrutide is investigational (in trials), while Semaglutide is fda-approved.
- Administration: Retatrutide — Subcutaneous injection (weekly); Semaglutide — Subcutaneous injection (weekly — Ozempic/Wegovy), Oral tablet (daily — Rybelsus).
- Frequency: Retatrutide is typically once weekly; Semaglutide is once weekly (injectable); once daily (oral Rybelsus).
- Research depth: this profile cites 6 sources for Retatrutide vs 4 for Semaglutide.
Can you stack Retatrutide and Semaglutide?
avoid: Do not combine — same receptor class, overdose risk
Both are GLP-1 receptor agonists. Combining them stacks the same mechanism, significantly increasing the risk of severe GI side effects (nausea, vomiting, gastroparesis) and potential hypoglycemia. There is no research justification for combining GLP-1 agonists. Use one at a time.
See the full compatibility matrixHow each works
Retatrutide
Across the Phase 2 trial (NEJM 2023, Jastreboff et al.) and the Phase 3 TRIUMPH registrational program (TRIUMPH-1 through -4), retatrutide has produced dose-dependent weight loss reaching ~28.3% at 80 weeks (TRIUMPH-1, 12 mg) and ~28.7% at 68 weeks in a knee-osteoarthritis population (TRIUMPH-4, 12 mg), alongside improvements in glycemia, blood pressure, lipids, and liver fat. The glucagon component is thought to add energy expenditure on top of the appetite suppression driven by GLP-1 and GIP. As of mid-2026, Phase 3 efficacy figures are topline (press-release/conference level) and not yet published in full peer-reviewed form.
Semaglutide
Semaglutide has robust clinical trial data — including the STEP and SUSTAIN trial series — demonstrating significant weight loss (15–20% body weight), glycemic control, and cardiovascular risk reduction. It works by mimicking the GLP-1 hormone, slowing gastric emptying, increasing insulin secretion, and reducing appetite via central nervous system signaling.
This comparison aggregates public research and structured profile data for informational purposes only. It is not medical advice and does not recommend either compound for human use. Consult a qualified healthcare provider before considering any peptide.