Retatrutide: Latest results are in - will it be available in the UK soon?
5-minute read | Information checked: 5 October 2026
Retatrutide is attracting plenty of attention, with research suggesting it could become another important option for medical weight management.
But behind the headlines is an essential distinction: retatrutide is still an investigational medicine. It is not approved for routine use or available commercially in the UK. Products being sold online as “retatrutide” are not an authorised treatment, and there is no guarantee they contain genuine retatrutide. [1,2]
So, how does it compare with Mounjaro and Wegovy, what are the latest results, and when might it become available safely?
What is retatrutide?
Retatrutide is a medicine being developed by Eli Lilly and studied as a once-weekly injection. It acts on three hormone receptors: GLP-1, GIP and glucagon.
These pathways are involved in appetite, blood glucose regulation and metabolism. Targeting all three is the reason retatrutide is described as a “triple agonist”. You may also see it called “GLP-3” online, although this is not a recognised scientific classification. [1,3]
How does it compare with Mounjaro and Wegovy?
The main difference is the number of hormone pathways each medicine targets.
Wegovy contains semaglutide and targets GLP-1 receptors. It is a licensed prescription medicine for weight management in the UK.
Mounjaro contains tirzepatide and targets both GLP-1 and GIP receptors. It is also a licensed prescription medicine for weight management in the UK.
Retatrutide targets GLP-1, GIP and glucagon receptors. It remains investigational and is not approved for routine use.
Mounjaro and Wegovy can be prescribed to suitable patients following a clinical assessment. Retatrutide remains available legally only through Lilly’s clinical trials. [1,4]
However, targeting more receptors does not automatically mean a medicine is safer or the best choice for everyone. The amount of weight lost is only one part of assessing a treatment.
Does retatrutide produce greater weight loss?
The results are encouraging.
In Lilly’s TRIUMPH-1 trial, adults with obesity, or overweight with a weight-related condition, who did not have diabetes lost an average of 28.3% of their starting body weight over 80 weeks at the highest studied dose. This headline figure uses an analysis estimating the effect when treatment is taken as intended; it is not a guaranteed outcome for an individual patient. [5]
For comparison, the SURMOUNT-5 trial directly compared tirzepatide with injectable semaglutide in adults with obesity without diabetes. Average weight loss at 72 weeks was 20.2% with tirzepatide and 13.7% with semaglutide, using the maximum tolerated doses studied. [6]
These figures may make retatrutide look more effective, but comparing separate trials cannot prove that one medicine is better. The participants, treatment duration, doses and methods of analysing results differ. Retatrutide was not included in SURMOUNT-5.
The research suggests substantial potential, while a fair comparison also needs to consider tolerability, health outcomes and longer-term safety.
What about side effects?
Retatrutide is not free from side effects. Clinical trials have reported digestive symptoms, including nausea, diarrhoea and vomiting. These are also familiar side effects of Mounjaro and Wegovy. [6,7]
Its safety profile is still being assessed. Promising weight-loss results do not replace the need for regulatory review, appropriate prescribing and ongoing monitoring.
When could retatrutide come to the UK?
There is currently no confirmed UK launch date.
Lilly has announced plans to submit retatrutide for US regulatory approval in the first quarter of 2027. That is a planned application date, rather than an approval or launch date, and it does not establish when the medicine might become available in the UK. [3]
UK availability would depend on the relevant regulatory review, authorisation and launch arrangements. 2027 or later is a possible scenario, rather than a confirmed timetable. Claims promising a specific UK release date should therefore be treated cautiously. Lilly states that launch depends on completion of the clinical development and regulatory approval process. [1]
Beware of people selling “retatrutide” online
The growing interest has created an opportunity for illegal sellers.
The MHRA has explicitly warned that retatrutide has not been authorised for use in the UK, and that people selling it are doing so illegally. Crucially, there is no guarantee that these products even contain retatrutide. [2]
A convincing label, professional-looking website or positive customer review cannot establish what is inside a vial or pen.
Products from illegal suppliers may contain different substances, incorrect amounts of an ingredient, or contamination such as bacteria. Their contents, quality and sterility cannot be assumed. [1,2]
“Research use only” does not mean safe for personal use. A product sold under that description is not an approved medicine for you to inject.
What if you have already bought some?
If you have purchased a product advertised as retatrutide, do not use it. If you have already taken it, speak to a healthcare professional and explain what you took, when you took it and where it came from. Keep the packaging or photographs to help identify the product.
Seek urgent medical help if you feel seriously unwell, and call 999 for a life-threatening emergency. Suspected side effects can also be reported through the MHRA Yellow Card scheme: https://yellowcard.mhra.gov.uk/
The MHRA encourages people experiencing suspected medicine side effects to speak with their doctor, pharmacist or nurse and submit a report. [8]
Safe weight management starts with safe treatment
At AJ Hill Aesthetics, we understand why new developments in weight management attract interest. Retatrutide’s research is promising, but patient safety must come before online hype.
For now, obtain prescribed weight-management medicines through a legitimate pharmacy following an assessment by an appropriate healthcare professional. The MHRA advises that this is the route to obtaining genuine medicines. [4]
If you are considering treatment or wondering whether your current medicine is right for you, speak with your prescriber. An individual review can help you understand your options and make an informed decision while research into future treatments continues.
References
[1] Eli Lilly. What to know about retatrutide. https://www.lilly.com/news/stories/what-to-know-about-retatrutide
[2] MHRA. No summer shortcut for safe weight loss (24 July 2026). https://www.gov.uk/government/news/no-summer-shortcut-for-safe-weight-loss
[3] Eli Lilly. TRIUMPH-2 detailed results and planned regulatory submission (29 September 2026). https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-substantial-weight
[4] MHRA. GLP-1 medicines for weight loss and diabetes: what you need to know. https://www.gov.uk/government/publications/glp-1-medicines-for-weight-loss-and-diabetes-what-you-need-to-know/glp-1-medicines-for-weight-loss-and-diabetes-what-you-need-to-know
[5] Eli Lilly. TRIUMPH-1 Phase 3 results (21 May 2026). https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss
[6] Aronne LJ et al. Tirzepatide as Compared with Semaglutide for the Treatment of Obesity. New England Journal of Medicine (2025). https://pubmed.ncbi.nlm.nih.gov/40353578/
[7] Eli Lilly. Additional Phase 3 retatrutide results (6 June 2026). https://lilly.gcs-web.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-drove-substantial-improvements
[8] MHRA. Largest seizure of unlicensed weight-loss medicines (29 May 2026). https://www.gov.uk/government/news/two-arrested-during-the-mhras-largest-ever-seizure-of-unlicensed-weight-loss-medicines
