Retatrutide: The Next Generation Weight Loss Injection
Retatrutide (sometimes searched as "retadrutide") is an investigational weight loss medicine that has produced some of the largest results seen in clinical trials to date. This guide from our Glasgow pharmacy team explains what it is, how it works, and how it compares to treatments such as Mounjaro.
Important: Retatrutide is not yet licensed or available in the UK. It is still in clinical trials and cannot currently be prescribed or dispensed by any pharmacy. This page is for information only. If you are ready to start treatment now, our pharmacists can discuss licensed options such as Mounjaro.
What is retatrutide?
Retatrutide is an experimental injectable medicine being developed by Eli Lilly for the treatment of obesity and related conditions. It is given as a once-weekly injection, similar to other modern weight management treatments.
What makes retatrutide stand out is that it acts on three of the body's appetite and metabolism hormone pathways at once. Because of this, researchers and the media often describe it as a "triple agonist" or the next step beyond the current generation of weight loss injections.
It is worth being clear from the outset: retatrutide has not completed the trials needed for approval. It is not available to buy or be prescribed in the UK, and any website offering to sell it should be treated with caution.
A triple-hormone approach
Most weight loss injections currently in use work on one or two hormone pathways. Retatrutide targets three, which is the main reason it has attracted so much research interest.
GLP-1
Reduces appetite and slows stomach emptying, helping you feel full for longer. This is the pathway used by Wegovy and Ozempic.
GIP
Supports blood sugar control and appetite regulation. GLP-1 and GIP together are how Mounjaro (tirzepatide) works.
Glucagon
The third pathway, unique to retatrutide, is thought to increase the amount of energy the body burns, on top of reducing appetite.
What do the trials show?
In a mid-stage (Phase 2) clinical trial published in 2023, participants taking the highest dose of retatrutide lost on average around a quarter of their body weight over roughly 11 months, alongside diet and lifestyle changes. These were some of the highest averages reported for a weight loss medicine in a trial of that kind.
Larger, longer Phase 3 trials are still ongoing. These bigger studies are needed to confirm how well retatrutide works, how safe it is over time, and which patients benefit most before any regulator can consider approving it.
As with all medicines in this class, side effects in the trials were most commonly digestive, such as nausea, and tended to be more likely at higher doses. The full safety picture will only be clear once the larger trials are complete.
Trial figures are approximate averages from published research and are included for general education. They are not a prediction of individual results.
Retatrutide vs the treatments available now
| Treatment | Hormone pathways | UK status |
|---|---|---|
| Retatrutide | GLP-1 + GIP + glucagon (triple) | In trials, not available |
| Mounjaro (tirzepatide) | GLP-1 + GIP (dual) | Licensed and available |
| Wegovy (semaglutide) | GLP-1 (single) | Licensed and available |
A newer mechanism does not automatically mean a better choice for any individual. The right treatment depends on your health, your goals and what is actually licensed and available. Read our full comparison of the injections you can get today, or learn about the other treatment on the horizon, the once-daily Wegovy pill (oral semaglutide).
Interested in retatrutide?
Because retatrutide is not yet licensed, no responsible UK pharmacy can supply it. If and when it does become available, it will only be appropriate after a proper clinical assessment. In the meantime, our GPhC-regulated pharmacists in Glasgow can assess your eligibility for licensed treatments such as Mounjaro, and you are welcome to ask us to keep you informed as the science develops.
Retatrutide FAQs
Can I buy retatrutide in the UK right now?
No. Retatrutide has not been approved by UK regulators and is not available from any legitimate pharmacy. It remains an investigational medicine in clinical trials. We would strongly advise against buying anything sold online as "retatrutide", as its safety and contents cannot be guaranteed.
Is retatrutide better than Mounjaro?
Early trial results for retatrutide have been very promising, but it has not finished the large trials needed to prove its long-term safety and effectiveness. Mounjaro is licensed, well studied and available now. The best treatment for you is the one that is suitable for your health and that you can actually access, which is something our pharmacists can help you work out.
When will retatrutide be available?
There is no confirmed date. It depends on the results of ongoing Phase 3 trials and a review by medicines regulators. That process can take a considerable time, and approval is never guaranteed for any medicine in trials.
How is retatrutide different from Mounjaro and Wegovy?
Wegovy works on one hormone pathway (GLP-1) and Mounjaro on two (GLP-1 and GIP). Retatrutide adds a third, glucagon, which is thought to help the body burn more energy. This triple action is the reason for the research interest, but it does not change the fact that it is not yet available.
This page is provided for general information and education only and does not constitute medical advice, a diagnosis or a recommendation to use any specific medicine. Retatrutide is an investigational product and is not licensed for use in the United Kingdom. Always speak to a qualified healthcare professional before making any decision about weight management treatment.