Retatrutide is shaping up to be the most powerful weight loss medication ever developed. In December 2025, Eli Lilly announced that its Phase 3 TRIUMPH-4 trial delivered an average of 28.7% body weight loss at 68 weeks — a result that surpasses anything semaglutide (Wegovy) or tirzepatide (Mounjaro) have achieved in clinical settings.
For people in the UK following the retatrutide clinical trial data closely, the natural question is: when will retatrutide actually be available here? The answer involves several regulatory milestones, and the honest truth is that we are still years away from UK availability. This guide breaks down exactly where things stand in February 2026, what needs to happen next, and what you can do in the meantime to optimise your metabolic health.
Key Takeaways
- Retatrutide is a triple-receptor agonist (GLP-1 + GIP + glucagon) that achieved 28.7% body weight loss in its first Phase 3 trial (TRIUMPH-4, December 2025).
- Seven additional Phase 3 trials are expected to report results throughout 2026, with the full programme completing by late 2026.
- Eli Lilly has not announced an official regulatory filing date. The earliest realistic FDA submission is late 2026 or early 2027.
- MHRA approval typically follows 4–12 months after FDA approval. UK availability is most likely in 2028, with private prescriptions potentially earlier than NHS access.
- NHS prescribing requires a separate NICE technology appraisal, which could add 6–18 months beyond MHRA approval.
- While you wait, baseline blood testing gives you actionable data about the metabolic markers that weight loss medications are designed to improve.
Where Retatrutide Stands Right Now (February 2026)
Retatrutide (development code LY3437943) is manufactured by Eli Lilly and is currently in Phase 3 clinical trials — the final and most extensive stage of drug development before a company can apply for regulatory approval. It has not been approved for any medical use in any country.
The drug works by mimicking three gut hormones simultaneously: GLP-1, GIP, and glucagon. This triple mechanism is what sets it apart from existing medications. Semaglutide targets one receptor; tirzepatide targets two; retatrutide targets all three. The addition of glucagon receptor activation appears to unlock unique effects on liver fat, energy expenditure, and total metabolic improvement that the earlier drugs cannot match.
The TRIUMPH Programme
Eli Lilly’s registrational trial programme for retatrutide is called TRIUMPH. It consists of eight Phase 3 trials evaluating the drug in people with obesity, type 2 diabetes, obstructive sleep apnoea, and knee osteoarthritis.
The first trial to report was TRIUMPH-4 in December 2025. In participants with obesity and knee osteoarthritis, the 12 mg dose delivered an average body weight loss of 28.7% (placebo-adjusted: 26.6%) at 68 weeks — equivalent to roughly 71 lbs (32.3 kg) on average. Retatrutide also produced significant reductions in knee pain, with more than one in eight patients becoming completely free of knee pain by the end of the trial.
The remaining seven trials, including TRIUMPH-1 and TRIUMPH-2 (the core obesity trials), are expected to read out by mid-to-late 2026. These trials will test doses of 4 mg, 9 mg, and 12 mg, including a maintenance dose strategy that could shape how the drug is prescribed long-term.
A new safety signal emerged in TRIUMPH-4: dysesthesia (an abnormal tingling or painful sensation in the skin) occurred in 8.8% of patients on the 9 mg dose and 20.9% on the 12 mg dose, compared to 0.7% on placebo. This finding will be closely scrutinised in the upcoming trials and will factor into any regulatory submission.
The UK Regulatory Pathway: MHRA and NICE
For a new drug to become available in the UK, it must clear two distinct regulatory hurdles:
1. MHRA Marketing Authorisation. The Medicines and Healthcare products Regulatory Agency (MHRA) must review the full clinical data package and grant a marketing authorisation. This is the legal permission to sell the drug in the UK. MHRA review typically takes around 150 working days (roughly 7–8 months) from the date of a valid submission. Eli Lilly can submit to the MHRA independently of the FDA, though UK submissions often follow the US filing by several months.
2. NICE Technology Appraisal (for NHS access). Even after MHRA approval, a drug is not automatically available on the NHS. The National Institute for Health and Care Excellence (NICE) must conduct a cost-effectiveness appraisal to determine whether the NHS should fund it. This process typically takes 6–18 months and hinges on cost-per-QALY thresholds. If retatrutide is deemed too expensive relative to the health benefits, NICE could restrict NHS access or recommend it only for specific patient populations (such as those with BMI above 40, or those with obesity-related comorbidities).
Private prescribing, by contrast, does not require NICE approval. Once the MHRA grants marketing authorisation, private clinics and pharmacies can prescribe and dispense the medication — provided they can source it. This is exactly how tirzepatide (Mounjaro) first became available in the UK: private providers were offering it months before the NHS roll-out.
Retatrutide UK Timeline: What to Expect
Based on Eli Lilly’s announced trial completion dates, historical regulatory timelines for semaglutide and tirzepatide, and standard MHRA/NICE review periods, here is the most realistic timeline:
| Milestone | Expected Date | Status |
|---|---|---|
| TRIUMPH-4 Phase 3 results (obesity + OA) | December 2025 | Complete |
| TRIUMPH-1, TRIUMPH-2 results (core obesity) | Mid-2026 | In progress |
| Remaining TRIUMPH trials complete | Late 2026 | In progress |
| FDA New Drug Application (NDA) submission | Late 2026 – Early 2027 | Pending |
| FDA approval (US) | Mid – Late 2027 | Pending |
| MHRA submission (UK) | 2027 | Pending |
| MHRA marketing authorisation (UK) | Late 2027 – Mid 2028 | Pending |
| Private prescriptions available (UK) | Late 2027 – 2028 | Pending |
| NICE technology appraisal complete | 2028 – 2029 | Pending |
| NHS prescriptions available (UK) | 2029 (earliest) | Pending |
Important caveat: These are projections based on publicly available information and historical precedent. Eli Lilly has not announced an official NDA filing date or MHRA submission timeline. Any unexpected safety findings, manufacturing delays, or regulatory requests for additional data could push these dates further out.
FDA vs MHRA: How Long Does the UK Wait?
Historically, the MHRA has approved obesity medications within months of the FDA, though the gap varies. Here is how the precedent looks for the two most relevant comparisons:
Tirzepatide (Mounjaro): The FDA approved tirzepatide for type 2 diabetes in May 2022. The MHRA followed with UK approval in September 2022 — a gap of approximately 4–5 months. The MHRA then separately authorised tirzepatide for weight management in November 2023.
Semaglutide (Wegovy): The FDA approved Wegovy for weight management in June 2021. The EMA approved it in January 2022, with the UK relying on European regulatory pathways at the time. More recently, the MHRA approved the higher 7.2 mg dose of Wegovy in January 2026 — making the UK the first country in the world to authorise this higher strength, even ahead of the FDA.
This is encouraging for retatrutide. The MHRA has shown a willingness to move quickly on obesity medications, and in some cases has acted before the FDA. However, Eli Lilly may choose to file with the FDA first and use those results to inform its MHRA submission. The most likely scenario is that UK approval follows the US by 4–12 months, depending on whether Lilly files simultaneously or sequentially.
Private Prescriptions vs NHS: Two Pathways to Access
Private Access
Once the MHRA grants marketing authorisation, private clinics and online pharmacies will be able to prescribe retatrutide. Based on the tirzepatide precedent, private availability could begin within weeks of MHRA approval. However, two factors will determine how quickly it reaches patients:
- Supply: Eli Lilly faced significant manufacturing and distribution challenges with tirzepatide in the UK. Demand far exceeded initial supply. The same could happen with retatrutide.
- Cost: No official UK pricing has been announced. Given that retatrutide is a novel triple-agonist with more complex manufacturing than existing GLP-1 drugs, analysts expect it to be priced at a premium. Private monthly costs for tirzepatide currently range from £150–£300 in the UK. Retatrutide could be higher, at least initially.
NHS Access
NHS availability requires NICE to recommend retatrutide as a cost-effective treatment. NICE will evaluate the drug’s clinical effectiveness, its cost relative to existing treatments (semaglutide and tirzepatide), and the overall budget impact on the NHS. If retatrutide is deemed too expensive or if NICE determines it does not offer sufficient additional benefit over cheaper alternatives, NHS access could be restricted to specific patient groups or denied entirely.
For context, NICE recommended tirzepatide for weight management in December 2024, roughly 13 months after MHRA approval for that indication. The roll-out was then further delayed by supply constraints. Retatrutide is likely to face a similar 12–18 month gap between MHRA approval and full NHS availability. If it reaches NHS patients before 2029, that would represent a best-case scenario.
A Warning About Unregulated Retatrutide
A number of online vendors are currently selling products labelled as “retatrutide” for “research use only.” These are not approved for human use. They are unregulated, untested for purity or potency, and potentially dangerous. The MHRA seized a record haul of illicit weight loss drugs in 2025, highlighting the scale of the problem.
There is no legitimate way to obtain retatrutide in the UK outside of a clinical trial. Anyone offering it for self-injection is selling an unregulated compound with no guarantee of what it contains. The risks include contamination, incorrect dosing, and the absence of medical monitoring for side effects.
What to Do While You Wait: The Case for Baseline Blood Testing
If retatrutide is still two to three years from UK availability, what can you do now? The most valuable step is to understand your current metabolic health through comprehensive blood testing. Here is why this matters:
Retatrutide does not work in a vacuum. The clinical trials measured far more than weight loss. They tracked improvements in HbA1c (blood sugar control), cholesterol levels, triglycerides, liver fat markers, kidney function, and inflammatory markers. To know whether a weight loss medication is actually improving your health — rather than just reducing the number on the scale — you need to know where those markers started.
Baseline testing gives you a starting point. If you take a comprehensive blood test today and another after starting any weight loss intervention (whether a GLP-1 medication, dietary changes, or exercise), you can objectively measure what is improving, what is not, and whether your approach needs adjusting.
You may discover issues that need attention now. Many people who are considering weight loss medication have undiagnosed metabolic conditions: prediabetes, fatty liver disease, thyroid dysfunction, or vitamin deficiencies. A blood test can surface these issues years before they cause symptoms, giving you the opportunity to intervene early.
Get Your Metabolic Baseline
Whether you are considering a weight loss medication or simply want to understand your health, a comprehensive blood test gives you the data to make informed decisions.
- Core Health 45 — 45 biomarkers including liver function, kidney function, cholesterol, HbA1c, thyroid, vitamins, and inflammation markers. The essential metabolic panel.
- Peak Insights 70 — 70 biomarkers for a deeper analysis, adding hormones, iron studies, and advanced cardiovascular risk markers. Ideal if you want the most complete picture before starting any intervention.
The biomarkers most relevant to retatrutide’s clinical effects include:
| Biomarker | Why It Matters | Included In |
|---|---|---|
| HbA1c | 3-month average blood sugar. Retatrutide reduced HbA1c by up to 2.0% in Phase 2. | Core Health 45, Peak Insights 70 |
| ALT, AST, GGT | Liver enzymes. Retatrutide reduced liver fat by 86% in Phase 2. Elevated enzymes often indicate fatty liver. | Core Health 45, Peak Insights 70 |
| Total cholesterol, LDL, HDL | Full lipid profile. TRIUMPH-4 showed significant reductions in non-HDL cholesterol. | Core Health 45, Peak Insights 70 |
| Triglycerides | Sensitive marker for metabolic improvement and fatty liver resolution. | Core Health 45, Peak Insights 70 |
| TSH, Free T4 | All GLP-1 agonists carry a precautionary warning about thyroid C-cell tumours. Baseline thyroid levels are essential. | Core Health 45, Peak Insights 70 |
| hsCRP | High-sensitivity C-reactive protein. A marker of systemic inflammation that improved significantly in TRIUMPH-4. | Peak Insights 70 |
| Creatinine & eGFR | Kidney function. Weight loss medications can cause dehydration, which affects kidney markers. | Core Health 45, Peak Insights 70 |
How Retatrutide Compares to Available Treatments
If you are unwilling to wait two to three years, semaglutide and tirzepatide are both available in the UK now. Here is how they compare on the metrics that matter most:
| Semaglutide (Wegovy) | Tirzepatide (Mounjaro) | Retatrutide | |
|---|---|---|---|
| Mechanism | GLP-1 (single) | GLP-1 + GIP (dual) | GLP-1 + GIP + Glucagon (triple) |
| Weight loss | ~15% | ~20–22% | ~24–29% |
| HbA1c reduction | 1.0–1.5% | 1.6–2.4% | 1.3–2.0% |
| Liver fat reduction | Modest | Moderate | Up to 86% |
| UK availability | Available now | Available now | Not available (est. 2028) |
| Private cost (monthly) | £150–£250 | £150–£300 | TBC (expected premium) |
For a deeper comparison of clinical data, mechanisms, and side effect profiles, read our full guide: Retatrutide vs Semaglutide vs Tirzepatide: Full Comparison.
If you are currently taking or considering semaglutide or tirzepatide, regular blood testing while on GLP-1 medication is strongly recommended to monitor liver function, blood sugar, nutritional status, and thyroid health.
Prepare Your Health Baseline While You Wait
While retatrutide awaits MHRA approval, establishing a comprehensive health baseline now means you will have pre-treatment data ready when the drug becomes available. A blood test covering HbA1c, liver function, lipids, kidney markers, and thyroid function gives you the starting reference that any prescriber will need.
All results reviewed by a doctor. Free delivery. Results in 2-3 working days.
Frequently Asked Questions
Is retatrutide available in the UK?
No. As of February 2026, retatrutide is not available in the UK. It is an investigational drug currently in Phase 3 clinical trials conducted by Eli Lilly. It has not been approved by the MHRA and cannot be legally prescribed or dispensed in the UK.
When will retatrutide be approved in the UK?
The most realistic estimate is late 2027 to mid-2028 for MHRA marketing authorisation. This assumes the remaining Phase 3 trials complete successfully by late 2026, Eli Lilly submits an NDA to the FDA in late 2026 or early 2027, and MHRA follows within 4–12 months. NHS availability through NICE could take until 2029.
Can I buy retatrutide online in the UK?
Some websites sell products labelled as retatrutide “for research use only.” These are not approved for human use, are not regulated by the MHRA, and carry serious safety risks including contamination, incorrect dosing, and the absence of medical supervision. We strongly advise against purchasing from any unregulated source.
How much will retatrutide cost in the UK?
No official pricing has been announced. Given its novel triple-agonist mechanism and premium positioning relative to tirzepatide, analysts expect retatrutide to be priced at or above current tirzepatide rates (£150–£300/month privately). NHS pricing will depend on negotiations between Eli Lilly and NHS England, as well as NICE’s cost-effectiveness assessment.
Will retatrutide be available on the NHS?
It is too early to say with certainty. If the MHRA approves retatrutide, NICE will need to conduct a technology appraisal to determine NHS funding. If it is recommended, access would likely be restricted to tier 3 specialist weight management services for patients meeting specific BMI and comorbidity criteria, similar to how semaglutide and tirzepatide are currently prescribed on the NHS.
How does retatrutide differ from semaglutide and tirzepatide?
Retatrutide is a triple-receptor agonist that targets GLP-1, GIP, and glucagon receptors simultaneously. Semaglutide (Wegovy/Ozempic) targets only GLP-1, while tirzepatide (Mounjaro/Zepbound) targets GLP-1 and GIP. The addition of glucagon receptor activation gives retatrutide unique effects on liver fat metabolism, energy expenditure, and overall weight loss. In clinical trials, retatrutide has produced approximately 28.7% body weight loss, compared to roughly 15% for semaglutide and 20–22% for tirzepatide. Read the full comparison here.
What blood tests should I get before starting a weight loss medication?
A comprehensive metabolic panel is recommended before starting any GLP-1 or GIP/glucagon agonist. Key markers include HbA1c (blood sugar), liver function (ALT, AST, GGT), lipid profile (cholesterol, triglycerides, HDL, LDL), kidney function (creatinine, eGFR), thyroid function (TSH, free T4), and key vitamins. Our Core Health 45 covers all of these in a single at-home test, while Peak Insights 70 adds hormones, iron studies, and advanced inflammatory markers for a more complete picture.
What are the side effects of retatrutide?
In the TRIUMPH-4 trial, the most common side effects were gastrointestinal: nausea, diarrhoea, constipation, and decreased appetite — consistent with other GLP-1 medications. A new safety signal was dysesthesia (abnormal tingling or painful skin sensation), affecting up to 20.9% of patients on the 12 mg dose. Full retatrutide side effect data is covered in our dedicated guide.
Do Not Wait to Understand Your Health
Retatrutide may be years away, but your metabolic data is available today. A comprehensive blood test gives you the baseline to track real progress — whether you start a medication, change your diet, or simply want to know where you stand.
Shop Core Health 45 Shop Peak Insights 70Last updated: February 2026 • Written by the Lola Health editorial team
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