✓ Medically reviewed by · Last reviewed: May 2026
Pharmacy Researcher · 8 years experience
Pharmacy researcher with 8 years reviewing clinical drug information, generic formulation equivalence, and international pharmaceutical standards. Focuses on patient-facing accuracy in medication education.
Key Takeaways — How to Get Retatrutide
- Retatrutide is a triple agonist (GIP + GLP-1 + glucagon receptors) — the most powerful weight-loss peptide in current clinical development, showing up to 24% body weight reduction at 48 weeks in Phase 2 trials (vs ~15% for tirzepatide, ~12% for semaglutide).
- Not yet FDA-approved — Eli Lilly’s Phase 3 trials (TRIUMPH program) are underway. No approved therapeutic use as of 2026.
- Available as research-grade peptide from MedsBase for laboratory and investigational use — supplied as lyophilised peptide with ≥98% purity, requiring reconstitution with bacteriostatic water.
- Reconstitution and handling requires sterile technique — review the BAC Water guide before use.
- Order Retatrutide from MedsBase — from $310 (research grade, lyophilised, worldwide shipping).
What Is Retatrutide?
Retatrutide (LY3437943) is a once-weekly injectable peptide developed by Eli Lilly that simultaneously activates three incretin and metabolic receptors:
- GIP receptor (GIPR) — glucose-dependent insulinotropic polypeptide; augments insulin secretion and reduces glucagon
- GLP-1 receptor (GLP-1R) — glucagon-like peptide-1; slows gastric emptying, reduces appetite, augments insulin, reduces glucagon
- Glucagon receptor (GCGR) — increases energy expenditure and hepatic fat oxidation; direct thermogenic and lipolytic effect
This triple mechanism is what separates retatrutide from its predecessors. Semaglutide (Ozempic/Wegovy) is a GLP-1 monoagonist. Tirzepatide (Mounjaro/Zepbound) is a dual GIP/GLP-1 agonist. Retatrutide adds glucagon receptor agonism — recruiting a third pathway that directly stimulates fat burning and energy expenditure beyond the appetite suppression seen with GLP-1 agonists alone.
Retatrutide Clinical Trial Results
The landmark Phase 2 trial (N=338, 48 weeks, published NEJM June 2023) showed retatrutide produced dose-dependent weight loss:
- 4 mg dose: average 8.7% body weight reduction
- 8 mg dose: average 17.5% body weight reduction
- 12 mg dose: average 24.2% body weight reduction at 48 weeks
At the 12 mg dose, 100% of participants achieved at least 5% weight loss, 83% achieved ≥10%, and 26% achieved ≥25% — results not seen with any other agent in clinical development. No weight plateau was apparent at 48 weeks, suggesting the curve was still descending.
Retatrutide vs Other Weight Loss Agents
| Drug | Mechanism | Average Weight Loss | Status |
|---|---|---|---|
| Retatrutide 12 mg | GIP + GLP-1 + Glucagon | ~24% at 48 weeks | Phase 3 (TRIUMPH program) |
| Tirzepatide 15 mg (Mounjaro) | GIP + GLP-1 | ~22% at 72 weeks (SURMOUNT-1) | FDA-approved (obesity) |
| Semaglutide 2.4 mg (Wegovy) | GLP-1 | ~15% at 68 weeks (STEP-1) | FDA-approved (obesity) |
| Orlistat 120 mg (Xenical) | Pancreatic lipase inhibitor | ~3–5% at 12 months | FDA-approved |
Retatrutide Dosing Protocol (Research Use)
Based on the Eli Lilly Phase 2 trial, the escalation protocol used was:
| Weeks | Dose | Purpose |
|---|---|---|
| Weeks 1–4 | 2 mg once weekly | Initial tolerability establishment |
| Weeks 5–8 | 4 mg once weekly | Dose escalation |
| Weeks 9–12 | 8 mg once weekly | Higher-dose range |
| Week 13+ | 12 mg once weekly | Maximum dose (trial highest group) |
Slow dose escalation is critical — retatrutide’s GLP-1 component causes nausea/vomiting proportional to rate of uptitration. The trial’s gradual 12-week ramp produced manageable GI side effects in most participants.
Reconstitution Guide
Retatrutide from MedsBase is supplied as lyophilised (freeze-dried) powder requiring reconstitution before subcutaneous injection. The full protocol is detailed in our BAC Water guide. Key points:
- Use bacteriostatic water (BAC water) for reconstitution — contains 0.9% benzyl alcohol as preservative, allowing multi-dose use over 28 days when stored at 4°C
- Inject BAC water slowly down the side of the vial — do not inject directly onto the lyophilised cake
- Swirl gently — do not shake (causes aggregation)
- Use 1 mL insulin syringes (31G) for subcutaneous injection
- Inject into abdomen, outer thigh, or upper arm — rotate sites each week
- Store reconstituted solution at 2–8°C for up to 28 days; protect from light
Retatrutide Side Effects (From Phase 2 Data)
- Nausea — most common (48% at 12 mg); typically peaks at dose escalation and reduces at maintenance
- Vomiting — 25% at 12 mg; manageable with slow escalation
- Diarrhoea — 16%; usually transient
- Constipation — 9%; GLP-1 class effect (slowed gastric motility)
- Injection site reactions — mild; erythema, bruising
- Increased heart rate — mild (3–5 bpm); GLP-1 class effect; resolve at stable dose
No pancreatitis, thyroid tumours, or cardiovascular events were observed at higher rates than placebo in the Phase 2 trial, though these must be evaluated in the larger Phase 3 program.
Where to Get Retatrutide
Retatrutide is available at MedsBase as a research-grade lyophilised peptide from $310. Sourced from WHO-GMP certified manufacturers, shipped worldwide in discreet packaging. All orders are covered by our Reshipment Assurance Policy.
Also browse our full peptides range including BPC-157, TB-500, CJC-1295/Ipamorelin stacks, and more.
Frequently Asked Questions
Is retatrutide FDA-approved?
No. As of 2026, retatrutide (LY3437943) is not FDA-approved for any indication. It is in Phase 3 clinical trials (Eli Lilly’s TRIUMPH program) for obesity and type 2 diabetes. The Phase 3 data readout is expected in 2026–2027. It is available as a research-grade peptide for laboratory and investigational use.
How does retatrutide differ from tirzepatide (Mounjaro)?
Tirzepatide is a dual GIP/GLP-1 agonist. Retatrutide adds glucagon receptor agonism as a third mechanism — glucagon receptor activation directly increases energy expenditure and hepatic fat oxidation (thermogenesis + lipolysis), which may explain retatrutide’s superior weight loss in Phase 2 vs tirzepatide at comparable durations.
What is the expected Phase 3 / approval timeline?
Based on Eli Lilly’s public statements, Phase 3 trials are actively enrolling as of 2025. Full data readout is expected around 2026–2027, with potential FDA submission and approval by 2027–2028 if trials succeed. This would make retatrutide potentially the most effective pharmaceutical weight-loss agent ever approved.
Can retatrutide help with type 2 diabetes, not just obesity?
The Phase 2 program included a diabetes cohort (non-insulin T2DM). Results showed significant HbA1c reduction alongside weight loss — consistent with its GLP-1 and GIP mechanisms. Eli Lilly is pursuing both obesity and T2DM indications in Phase 3.
What does it mean that retatrutide is “research grade”?
Research-grade peptides are produced to high purity standards (≥98% by HPLC) and are suitable for in-vitro and in-vivo laboratory research. They are not manufactured under clinical-grade GMP conditions and are not intended for therapeutic use in humans under the current regulatory framework. Purchasers are responsible for ensuring their use complies with applicable local regulations.
How is retatrutide administered?
Subcutaneous injection, once weekly. The lyophilised research-grade form requires reconstitution with bacteriostatic water before injection. Administer into the abdomen, outer thigh, or upper arm using a 31G insulin syringe. Rotate injection sites weekly.
Research Use Disclaimer: Retatrutide is supplied as a research-grade peptide for laboratory and investigational purposes only. It is not approved for human therapeutic use. This information is for educational and research reference only. Individuals considering off-label use should consult qualified medical professionals and be aware of applicable local regulations.
Written by
Sophie ChenPharmaceutical Content Researcher · 8 years experience
Sophie Chen is a pharmaceutical content researcher with 8 years covering generic medication access and clinical pharmacology. She specialises in international regulatory frameworks, bioequivalence standards, and patient-facing education on therapeutic drug classes. She is not a clinician.