What Is Retatrutide? The Simple UK Guide
Last updated 13 June 2026 · How we check our facts
Quick answer
Key facts
- Type
- Triple receptor peptide
- Targets
- GLP-1, GIP, glucagon
- Made by
- Eli Lilly
- Research status
- Phase 3 trials (2026)
- UK status
- Research use only
- A medicine?
- No, not approved
- Also sold as
- Retaklik
- Trial dosing
- Once-weekly injection
What retatrutide is
Retatrutide is a small, lab-made chain of amino acids. Think of it as a copy of signals your body already uses. Those signals help control hunger and blood sugar. Because it copies three of them at once, scientists call it a "triple agonist". Agonist just means "switch on".
You may also see it sold under the brand name Retaklik in the UK. That is the same peptide. The only way to be sure what is in a vial is to read its Certificate of Analysis.
What it does in studies
Retatrutide is being tested by Eli Lilly in a large set of trials. In an early Phase 2 study, published in the New England Journal of Medicine in 2023, adults in the study lost up to 17.5% of their body weight over 24 weeks. Later Phase 3 trials in 2025 and 2026 showed even larger results. We break down the numbers on our results page.
These were research results in controlled trials. They are not a promise of what any one person would get, and the peptide is not approved for people to take.
How it works (the simple version)
Retatrutide turns on three "manage my hunger and sugar" signals together:
- GLP-1 — the "I'm full" signal.
- GIP — helps the body handle sugar.
- Glucagon — helps the body burn stored energy.
That third signal is the special part. Read the full breakdown in how retatrutide works.
How it compares
Is it legal in the UK?
It is sold for research only. It is not approved for people to take. See retatrutide UK legal status for the full picture.
The full guide
Every page below answers one question in plain English:
- How retatrutide works
- Retatrutide vs Tirzepatide
- Retatrutide vs Semaglutide
- Clinical trials (TRIUMPH)
- Results and weight loss
- Side effects
- Half-life and timing
- Dosing in studies
- Storage and mixing
- Is it legal in the UK?
- Cost in the UK
Looking at suppliers?
What a trustworthy UK supplier looks likeCommon questions
Is retaklik the same as retatrutide?+
Retaklik is a brand name some UK suppliers use for retatrutide. The peptide inside is retatrutide. Always check the Certificate of Analysis (COA) to confirm what you are buying.
What does retatrutide target?+
It switches on three receptors at once: GLP-1, GIP, and glucagon. Most weight-loss research peptides only act on one or two. That third signal is what makes retatrutide stand out.
Is retatrutide a medicine?+
No. As of 2026 it is still in clinical trials run by Eli Lilly. It is not an approved medicine in the UK or anywhere else. It is sold here for laboratory research only.
What is a GLP-3?+
GLP-3 is an informal nickname the media uses for triple agonists like retatrutide. It is not a real drug class. The correct term is triple receptor agonist.
Who makes retatrutide?+
Eli Lilly is developing retatrutide. Inside trials it is given as a once-weekly injection under the skin.