Retatrutide is the drug people keep hearing about. This article is here to explain what it actually is, what the evidence currently shows, and — most importantly — why buying it from an online seller is a bad idea. Retatrutide is not licensed in the UK and is not available from Solira.
What retatrutide is
Retatrutide is an investigational medicine being developed by Eli Lilly. Where Mounjaro (tirzepatide) is a dual agonist acting on GLP-1 and GIP receptors, retatrutide is a triple agonist — it adds activity at the glucagon receptor. The theory is that glucagon receptor activity increases energy expenditure alongside the appetite suppression provided by the other two mechanisms.
Its licensing status in the UK
This needs to be said plainly: retatrutide is not licensed by the MHRA. It is not approved for use, it cannot be lawfully prescribed as a licensed medicine in the UK, and it is not available from any UK pharmacy, including Solira. It remains in clinical trials.
What the trial data shows so far
Phase 2 trial results published in the New England Journal of Medicine in 2023 reported substantial weight loss at higher doses over 48 weeks. That is why retatrutide has attracted so much attention.
It's worth being careful with what that actually means. Phase 2 results are early, involve relatively small numbers of participants, and are designed to establish signal and dose range — not to confirm long-term efficacy or safety. Phase 3 trials are required before any regulator will consider approval, and many drugs with promising phase 2 data do not reach approval.
Why you should not buy retatrutide online
This is the most important section of this article. If you are searching for retatrutide, you will find people offering to sell it. Do not buy it. Here is why:
- Products sold online as retatrutide are typically marketed as "research chemicals" or "not for human consumption". This is a deliberate legal evasion — a way to sell an unlicensed medicine without falling under medicines regulation.
- They are manufactured outside any regulated pharmaceutical supply chain, with no guarantee of identity, purity, sterility or dose. What is in the vial may not be what is on the label.
- There is no pharmacovigilance. If something goes wrong, there is no recall mechanism, no batch trace, and no one to report a serious reaction to.
- Dosing information circulating in online communities is not clinically validated. It is anecdote, not evidence.
- Injecting an unregulated peptide of unknown concentration carries real risk of infection, contamination and dosing error — including serious harm.
- A UK pharmacy cannot lawfully supply retatrutide. Any seller claiming otherwise is not operating within UK medicines law.
What you can actually get in the UK right now
If retatrutide caught your attention because of the weight loss figures, it's worth putting those numbers next to what's already licensed and available. The gap is smaller than the headlines suggest — and one side of the comparison has completed phase 3 trials, carries regulatory approval, and can be dispensed by a UK pharmacy today.
| Treatment | Average weight loss in trials | Trial stage | Available in the UK? |
|---|---|---|---|
| Retatrutide (triple agonist) | Around 24% at the highest dose at 48 weeks | Phase 2 — early, small numbers | No — not MHRA licensed |
| Mounjaro / tirzepatide (dual agonist) | Around 22.5% at 15mg over 72 weeks (SURMOUNT-1) | Phase 3 complete, licensed | Yes |
| Wegovy / semaglutide (GLP-1 agonist) | Around 15% at 2.4mg over 68 weeks (STEP-1) | Phase 3 complete, licensed | Yes |
Retatrutide's phase 2 figure and Mounjaro's phase 3 figure come from different trials, in different populations, over different timeframes — they are not directly comparable, and phase 2 results routinely soften in larger phase 3 studies. What is directly comparable is that tirzepatide beat semaglutide head-to-head in SURMOUNT-5, producing around 20.2% weight loss against 13.7%. That is the strongest weight loss evidence currently backed by a completed head-to-head trial and a UK licence.
Are you eligible?
Licensed GLP-1 treatment is available in the UK if you meet the clinical criteria. Broadly, that means:
- A BMI of 30 or above, or
- A BMI of 27 or above alongside a weight-related condition such as high blood pressure, type 2 diabetes, high cholesterol or obstructive sleep apnoea
- You must be 18 or over, not pregnant or breastfeeding, and free of certain contraindications such as a history of pancreatitis or medullary thyroid carcinoma
Eligibility is confirmed through a consultation reviewed by a pharmacist, not by a form. If you are not suitable, we will tell you and explain why.
Check if you're eligible
Free online consultation, reviewed by a GPhC-registered pharmacist. No obligation and no consultation fee.
Check my eligibility →When might retatrutide be available?
Honestly: no one knows. Phase 3 trials are ongoing. Any UK availability would require MHRA approval, which has not happened. Anyone giving you a confident date is guessing.
The people selling "retatrutide" online are not offering early access to a promising new medicine. They are selling an unregulated peptide of unknown quality, outside medicines law, with no safety net if something goes wrong.
When to see your pharmacist or doctor
- Retatrutide is not licensed or available in the UK. Do not buy peptides marketed as retatrutide from online sellers.
- If you have already used an unregulated product and feel unwell, seek medical advice and tell the clinician exactly what you took, when, and at what dose you believe.
- For licensed weight loss medication, speak to a UK-registered prescriber and use a GPhC-registered pharmacy.
Frequently asked questions
Is retatrutide available in the UK? No — it is not MHRA licensed and is not available from UK pharmacies.
Is retatrutide legal to buy? Products sold online are unregulated and are typically labelled as research chemicals to evade medicines law. They are not licensed medicines and buying them carries real risk.
Is retatrutide better than Mounjaro? Early phase 2 data attracted attention, but there is no head-to-head trial and no approval. Comparisons at this stage are speculative.
When will retatrutide be approved? Phase 3 trials are ongoing; no approval date exists.
Can Solira prescribe retatrutide? No. It is not a licensed medicine in the UK.
What can I take instead of retatrutide? Licensed options in the UK include tirzepatide (Mounjaro) and semaglutide (Wegovy, as an injection or tablet). Both have completed phase 3 trials and are available from a GPhC-registered pharmacy following a consultation. Eligibility depends on your BMI and medical history.
References
- Jastreboff AM et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med 2023.
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med 2022.
- Aronne LJ et al. Tirzepatide versus Semaglutide for the Treatment of Obesity (SURMOUNT-5). N Engl J Med 2025.
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP-1). N Engl J Med 2021.
- NICE guidance on overweight and obesity management.
- MHRA guidance on unlicensed medicines and on buying medicines safely online.
- General Pharmaceutical Council register.
Reviewed by Jimah Alsaai MPharm, GPhC 2232652, Superintendent Pharmacist, Solira.