What is Retatrutide? Triple Agonist Explained
Retatrutide is an investigational medication being studied for weight loss and type 2 diabetes. As a "triple agonist," it targets three hormone receptors that may produce greater weight loss than current medications. Here's what we know so far.
Important: Retatrutide is NOT Approved
Retatrutide is currently in Phase 3 clinical trials and is not approved for use in any country. It cannot be legally prescribed or purchased. This information is educational only. If you're interested in weight loss treatment, speak with your doctor about currently available options.
Retatrutide in Simple Terms
Retatrutide (pronounced reh-ta-TROO-tide) is an experimental weight loss medication being developed by pharmaceutical company Eli Lilly. Its development code is LY3437943.
What makes retatrutide unique is that it's a "triple agonist" - it activates three different hormone receptors in the body. This is one more than tirzepatide (Mounjaro), which activates two, and two more than semaglutide (Wegovy/Ozempic), which activates one.
Understanding Agonist Types
How Retatrutide Works
Retatrutide activates three hormone receptors, each contributing different effects on metabolism and appetite:
Effect: Reduces appetite, slows stomach emptying, improves blood sugar control. This is the same mechanism as Wegovy and Ozempic.
Effect: Enhances insulin release, may improve fat metabolism. Combined with GLP-1 in Mounjaro, thought to enhance weight loss effects.
Effect: May increase energy expenditure (calorie burning). This is the "new" component not found in current approved medications.
The theory is that combining all three pathways could lead to greater weight loss than targeting just one or two. The glucagon component may help the body burn more calories, while the GLP-1 and GIP components reduce appetite and improve metabolic health.
Note: This explanation is simplified. The actual pharmacology is complex, and researchers are still studying exactly how these pathways interact. The clinical benefit of adding glucagon receptor activation is being tested in ongoing trials.
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Why Researchers Are Interested
Retatrutide has generated significant interest due to preliminary trial results suggesting it may produce greater weight loss than currently available medications:
- ~24% average weight loss at highest dose (48 weeks)
- Significant HbA1c improvements in diabetes patients
- Dose-dependent response (higher dose = more effect)
Caveat: Phase 2 trials have smaller participant numbers. Results may differ in larger Phase 3 trials.
- Phase 2 data only - not yet confirmed in Phase 3
- Individual results vary significantly
- Long-term safety data not yet available
- Trial conditions differ from real-world use
Development Status
Developer
Eli Lilly and Company (same company that makes Mounjaro/tirzepatide)
Development Code
LY3437943 (no brand name yet as not approved)
Trial Programme
TRIUMPH (Phase 3 trials for obesity and type 2 diabetes)
Current Phase
Phase 3 clinical trials (ongoing as of December 2025)
UK Availability Status: NOT AVAILABLE
- • Not approved by MHRA
- • Not available on NHS
- • Not available through private prescription
- • No legitimate UK source exists
Alternatives Available Now
If you're interested in weight loss treatment, these medications are currently approved and available in the UK:
~21% average weight loss in trials. Available on NHS and privately.
~15% average weight loss in trials. Available on NHS and privately.
Our recommendation: If you're considering weight loss medication, speak with your GP or a specialist about currently available options. Waiting for an unapproved drug that may be years away from market could delay beneficial treatment.
Frequently Asked Questions
Related Guides
References & Sources
- Jastreboff AM, et al. Triple-hormone-receptor agonist retatrutide for obesity - A Phase 2 trial. NEJM 2023.
- Rosenstock J, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes. Lancet 2023.
- ClinicalTrials.gov. TRIUMPH Programme - Retatrutide Phase 3 trials.
- Eli Lilly. Retatrutide development programme press releases.
Medical Disclaimer
This information is provided for educational purposes only and is not intended as medical advice. Retatrutide is an investigational medication that is NOT approved for use. Do not attempt to obtain or use this medication. If you are interested in weight loss treatment, consult with a qualified healthcare professional about currently available, approved options.
Last updated: December 2025
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