Retatrutide UK: Complete Guide
Retatrutide is an investigational triple-agonist medication for weight loss and type 2 diabetes. It is not yet approved in the UK. This guide covers what we know so far, expected timelines, and how it compares to existing treatments.
Drug Class
Triple agonist (GLP-1/GIP/Glucagon)
Manufacturer
Eli Lilly
UK Status
Not approved (Phase 3 trials)
Trial Results
Up to 24.2% weight loss
What is Retatrutide?
Retatrutide (also known by its research code LY3437943) is an investigational medication being developed by Eli Lilly for the treatment of obesity and type 2 diabetes. It belongs to a new class of drugs called triple agonists.
Unlike existing medications such as Ozempic (semaglutide) which target only the GLP-1 receptor, or Mounjaro (tirzepatide) which targets GLP-1 and GIP receptors, Retatrutide activates three receptors simultaneously: GLP-1, GIP, and glucagon.
This triple mechanism of action may provide enhanced metabolic benefits, including greater weight loss, improved blood sugar control, and potential benefits for liver health. However, Retatrutide is still under investigation and not yet approved for use anywhere in the world.
UK Availability and Approval Timeline
Not Currently Available
Retatrutide is not approved by the MHRA and cannot be legally prescribed or purchased in the UK. Any products claiming to be Retatrutide sold online are unregulated and potentially dangerous.
Expected Timeline
2023-2024
Phase 2 trial results published showing up to 24.2% weight loss. Phase 3 trials (TRIUMPH programme) ongoing.
2025
Phase 3 trial results expected. Regulatory submissions to FDA and EMA may follow if results are positive.
2026 or later
Potential MHRA approval and UK availability. Timelines depend on trial outcomes and regulatory review processes.
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How Retatrutide Works
Retatrutide's triple-agonist mechanism targets three hormone receptors that play key roles in metabolism and appetite regulation:
Reduces appetite, slows gastric emptying, and improves insulin secretion. The same target as Ozempic and Wegovy.
Enhances insulin response and may improve fat metabolism. Also targeted by Mounjaro (tirzepatide).
Increases energy expenditure and fat breakdown. This is unique to Retatrutide among weight loss medications.
Retatrutide vs Other GLP-1 Medications
How does Retatrutide compare to currently available weight loss medications in the UK?
| Medication | Mechanism | Weight Loss | UK Status |
|---|---|---|---|
| Retatrutide | GLP-1 + GIP + Glucagon | ~24% (Phase 2) | Not Approved |
| Tirzepatide (Mounjaro) | GLP-1 + GIP | ~21% | Approved |
| Semaglutide (Wegovy) | GLP-1 | ~15% | Approved |
| Semaglutide (Ozempic) | GLP-1 | ~12% | Approved (T2D) |
Note: Weight loss percentages are from clinical trials and may vary. Direct head-to-head comparisons between these medications are limited.
Side Effects and Safety
Based on Phase 2 trial data, Retatrutide shares similar side effects to other GLP-1 medications. Most side effects are gastrointestinal and tend to be mild to moderate, decreasing over time.
- Nausea (especially during dose escalation)
- Diarrhoea
- Vomiting
- Constipation
- Decreased appetite
- Gallbladder problems
- Pancreatitis (rare)
- Hypoglycaemia (with other diabetes medications)
- Long-term effects still being studied
Frequently Asked Questions
Related Guides
All Retatrutide Guides
References & Sources
- Jastreboff AM, et al. (2023). Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine.
- Eli Lilly. Retatrutide Clinical Trials (TRIUMPH Programme). ClinicalTrials.gov.
- MHRA. Guidance on unlicensed medicines. gov.uk.
Medical Disclaimer
This information is provided for educational purposes only and is not intended as medical advice. Retatrutide is not approved for use in the UK and should not be purchased from unregulated sources. Always consult with a qualified healthcare professional before considering any weight loss medication. Information about investigational drugs may change as new research becomes available.
Last updated: December 2025
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