For Research Purposes Only. This page summarizes published preclinical and clinical research. It does not constitute medical advice and is not a recommendation for human use.
Retatrutide
Tri-agonist targeting GLP-1, GIP, and glucagon receptors simultaneously. Phase II data reported the highest mean weight loss of any single compound studied to date.
- Class
- Triple GLP-1 / GIP / Glucagon Agonist
- Developer
- Eli Lilly (LY3437943)
- Trial Phase
- Phase III (ongoing)
- Phase II Weight Loss
- 24.2% at 48 wks (12mg dose)
01 · Overview
Retatrutide (LY3437943) is a 36-amino-acid synthetic peptide developed by Eli Lilly that simultaneously activates three receptors: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and the glucagon receptor. This tri-agonist profile represents the next incremental step in the incretin-based drug development trajectory that began with GLP-1 agonists and advanced to dual GIP/GLP-1 agonists with tirzepatide. The addition of glucagon receptor agonism is theorized to further increase energy expenditure through thermogenesis and enhanced fat oxidation, on top of the appetite suppression and insulin sensitization shared with GLP-1-class agents. Glucagon receptor agonism also has established lipid-lowering and hepatic fat-reducing effects, which may be particularly relevant for metabolic liver disease applications.
Phase II clinical trial results published in the New England Journal of Medicine (Jastreboff et al., 2023) generated significant scientific attention. The trial enrolled 338 adults with obesity and randomized participants to five doses of retatrutide (1mg, 4mg, 8mg, or 12mg weekly) or placebo. At 48 weeks, mean weight loss at the 12mg dose reached 24.2%, with a remarkable 26.2% reduction observed in the completer analysis. Simultaneously, significant reductions were observed in waist circumference, liver fat fraction (−81.7% in a subset), triglycerides, and blood pressure. These results exceeded the 68-week Phase III data from semaglutide and the 72-week Phase III data from tirzepatide, both of which had shorter treatment durations — direct comparison requires caution, but the scale of effect was notable.
Retatrutide entered Phase III clinical development in 2023 under multiple registered trials for obesity, type 2 diabetes, and metabolic dysfunction-associated steatohepatitis (MASH). As of early 2026, it has not received FDA approval and remains an investigational compound. Research-grade retatrutide sold by peptide vendors is distinct from the investigational pharmaceutical compound and is intended exclusively for laboratory research purposes.
Sizes currently sold by tracked vendors: 1000mg, 100mg, 10mg, 120mg, 12mg, 150mg, 15mg, 200mg, 20mg, 240mg, 24mg, 300mg, 30mg, 400mg, 40mg, 480mg, 48mg, 500mg, 50mg, 5mg, 600mg, 60mg, 65mg, 6mg.
02 · Research status
Jastreboff et al. (NEJM 2023): Phase II, 338 adults with obesity. 24.2% mean weight loss at 48 weeks (12mg/week); 81.7% reduction in liver fat in assessed subset. Multiple Phase III trials registered at clinicaltrials.gov (search: retatrutide). Ongoing MASH and T2D trials.
03 · Common research protocols
| Phase II dose range | 1mg, 4mg, 8mg, or 12mg/week |
| Phase II titration schedule | Escalated over ~24 weeks to target dose |
| Administration (investigational) | Once-weekly subcutaneous injection |
| Typical research vial sizes | 2mg, 5mg, 10mg |
| Reconstitution solvent | Bacteriostatic water; requires manual reconstitution unlike investigational drug product |
Dosing above is from the published Phase II clinical trial protocol. Retatrutide has not been approved and does not have established prescribing information. Research-grade vials require reconstitution and are not equivalent to the investigational pharmaceutical compound. This is for educational reference only.
Use the reconstitution calculator →04 · Storage & handling
Store lyophilized research retatrutide at −20°C. Once reconstituted, store at 4°C and use within 28 days. Avoid freeze-thaw cycles after reconstitution.
05 · What to look for when buying
- Retatrutide is the most structurally complex peptide in the GLP class currently tracked by PepVendors — a 36-amino-acid molecule with a tri-receptor profile. Synthesis complexity means purity and fill accuracy vary more than with simpler compounds. Third-party HPLC testing is essential.
- Finnrick Analytics has begun testing retatrutide from vendors. Given that it is newer to market, the number of independently tested batches per vendor may be limited — factor this into your confidence level when assessing quality.
- Because retatrutide is still investigational (no FDA approval), it is a newer and less-established market. The vendor landscape is earlier-stage than for semaglutide or tirzepatide. Exercise additional scrutiny on vendor history and COA documentation.
- Retatrutide's Phase II data involved escalating doses over 24 weeks to reach the maximum. The research vial sizes (2mg, 5mg) reflect the lower end of this titration range. Verify vial concentration matches the stated label before any research use.
- As with all GLP-1 class peptides, verify that the COA specifies HPLC purity (not just mass spec identity) and that it includes fill/quantity accuracy data.
06 · Price comparison
Prices last checked Oct 26, 2026| Vendor | Sizes | Price range | Best $/mg | Stock |
|---|---|---|---|---|
| HkRoids | 8 | $71.00 – $380.00 | $0.63 | In stock |
| SaiyanMed | 8 | $85.00 – $400.00 | $0.72 | In stock |
| Zen Peptides | 5 | $70.00 – $280.00 | $0.93 | In stock |
| UWA Elite Peptides | 6 | $125.00 – $560.00 | $0.93 | In stock |
| Royal Peptides | 16 | $36.00 – $1200.00 | $1.20 | In stock |
| Oupeptide | 5 | $115.00 – $380.00 | $1.27 | In stock |
| Reta-Peptide | 1 | $135.00 | $1.35 | In stock |
| Sunrise BioResearch | 3 | $52.48 – $472.32 | $2.36 | In stock |
| Go Alpha Labs | 12 | $38.49 – $1518.99 | $2.53 | In stock |
| NUPEPS | 5 | $68.50 – $250.00 | $3.14 | In stock |
| Peptide Partners | 6 | $124.00 – $1512.00 | $3.15 | In stock |
| Accelerate Labs | 2 | $60.99 – $119.99 | $4.00 | In stock |
| Nextwave Peptides | 9 | $69.00 – $429.00 | $4.29 | In stock |
| Prime Peptides | 3 | $110.00 – $325.00 | $5.42 | In stock |
| Steady Meds | 8 | $50.00 – $350.00 | $5.83 | In stock |
| Amino Amigos | 2 | $95.00 – $385.00 | $5.92 | In stock |
| Coastal Peptides | 2 | $79.00 – $179.00 | $5.97 | In stock |
| Hydro Research | 5 | $65.00 – $530.00 | $8.75 | In stock |
| Injectify | 2 | $98.99 – $186.99 | $9.35 | In stock |
| Simple Peptide | 4 | $75.00 – $449.00 | $9.35 | In stock |
| PeptiSlim | 5 | $150.00 – $390.00 | $13.00 | In stock |
| Peptides 4 Research | 1 | $143.00 | $14.30 | In stock |
| Mei Peptide | 3 | $120.00 – $230.00 | $15.33 | In stock |
| Alpha-Gen | 1 | $119.99 | $24.00 | In stock |
| Behemoth Labz | 1 | $377.32 | $37.73 | In stock |
25 vendors tracked · prices scraped weekly from vendor sites · open full comparison table →
07 · Third-party purity data
Full data at finnrick.com ↗Independent HPLC test results — averages across multiple samples.
08 · Frequently asked questions
What is Retatrutide?
Retatrutide (LY3437943) is a 36-amino-acid synthetic peptide developed by Eli Lilly that simultaneously activates three receptors: GLP-1 (glucagon-like peptide-1), GIP (glucose-dependent insulinotropic polypeptide), and the glucagon receptor.
Is retatrutide FDA approved?
No — retatrutide is an investigational compound in Phase III trials (obesity, type 2 diabetes, MASH) as of early 2026. No NDA has been approved, and research-grade vials are laboratory reagents only.
How much does Retatrutide cost?
Across 25 vendors tracked by PepVendors, Retatrutide currently runs $0.63–$37.73 per mg at each vendor's best price tier (25 showing in stock). Vial prices and size tiers vary — the live comparison table on this page lists current pricing.
Which vendors have third-party purity data for Retatrutide?
Independent labs (Finnrick Analytics, Janoshik) have published HPLC purity results for 33 samples of Retatrutide or its components: Nuscience Peptides (99.9%), Loti Labs (99.9%), Peptide Partners (99.8%), Coastal Peptides (99.8%), Sunrise BioResearch (99.8%), NextechLabs (99.8%), SaiyanMed (99.8%), PeptiSlim (99.8%), Reta-Peptide (99.7%), Biolongevity Labs (99.7%), UWA Elite Peptides (99.7%), Peptide Crafters (99.7%), HkRoids (99.7%), Oupeptide (99.6%), Alpha-Gen (99.6%), Mei Peptide (99.6%), Liberty Peptides (99.5%), Royal Peptides (99.5%), Polaris Peptides (99.5%), Zen Peptides (99.5%), Paramount Peptides (99.5%), NUPEPS (99.5%), Hydro Research (99.4%), Nexaph (99.4%), Simple Peptide (99.4%), Injectify (99.1%), Amino Amigos (98.9%), Pure Rawz (98.2%), Prime Peptides (98.0%), Oasis Labs (97.4%), Verified Peptides (97.3%), Eternal Peptides (97.1%), Peptide Sciences (75.2%). A grade A (≥98%) is the appropriate baseline for research use — check the linked lab reports for batch-level detail and fill-accuracy data.