Retatrutide

Retatrutide is an investigational weight loss medication showing promising results in reducing body weight in adults with obesity or overweight. It's part of a new generation of drugs that help people lose weight by targeting multiple hormonal pathways that control appetite, metabolism, and energy balance. As of early 2026, Retatrutide is in Phase 3 clinical trials, which is the final stage of testing before the developing company, Eli Lilly, can seek FDA approval. Unlike other weight-loss injections, Retatrutide is a triple hormone receptor agonist, meaning it acts on three key receptors in hunger and metabolic regulation. That's why it's known as a “triple G.”

Retatrutide works by mimicking three hormones in the body:

• GLP-1 (Glucagon-Like Peptide-1): Slows down how fast your stomach empties, keeping you fuller for longer. This is the same hormone targeted by Wegovy and Ozempic.
• GIP (Glucose-Dependent Insulinotropic Polypeptide): Helps your body secrete insulin more effectively in response to meals. Also helps direct nutrients toward energy rather than storing them in fat cells. Dependent insulinotropic polypeptide (GIP) is also found in Mounjaro.
• Glucagon: Encourages the body to pull energy from stored fat. It's the most unique part of Retatrutide that no other weight loss medication has.

This triple-action approach by Retatrutide helps:

• Suppress appetite and cravings
• Slow digestion, making you feel full longer
• Regulate blood sugar levels
• Boost fat burning and metabolic function

Together, these mechanisms support weight loss and weight management when you combine them with diet and lifestyle changes.

Retatrutide is currently undergoing phase 3 clinical trials, the final stage before a medication can be approved for public use. Current trials include participants with obesity, both with and without related conditions such as osteoarthritis or sleep apnoea.

Key Findings So Far:

• Phase 2: Slows down how fast your stomach empties, keeping you fuller for longer. This is the same hormone targeted by Wegovy and Ozempic.
• Early phase 3: Results released in late 2025 suggest people may lose up to an average of 28.7% of body weight with long‑term treatment (68 weeks).
• Weight Loss Outcomes: Exceed those seen with many other weight loss medications, including dual‑action agents such as tirzepatide. Investigational research is still underway to explore future applications.

Clinical References:

• New England Journal of Medicine: Retatrutide Phase 2 obesity trial
• ClinicalTrials.gov: Ongoing Retatrutide studies
• Eli Lilly: Phase 3 TRIUMPH program updates

If approved, treatment with Retatrutide may be suitable for:

• Adults with Obesity: BMI ≥30
• Adults who are Overweight: BMI ≥27 with related health conditions such as fatty liver disease, type 2 diabetes, sleep apnea, high blood pressure, or high cholesterol.
• History of Failed Weight Loss: People who have not achieved enough weight loss through diet and exercise alone. Most insurance companies and clinical trials require that you have tried a supervised diet and exercise program for at least three to six months.

Who Might Not Be Eligible:

Current clinical research shows the following people may not be eligible for Retatrutide:

• Certain Medical Conditions: People with specific medical conditions, e.g., previous pancreatitis, specific cancers, or severe gastrointestinal disorders.
• Pregnancy & Breastfeeding: Those who are pregnant, planning to become pregnant soon, or breastfeeding.
• Age: People under 18.

Note: Official prescribing information and healthcare providers will determine final eligibility for Retatrutide if approved.

Retatrutide is being studied as a once-weekly injection, similar to other weight loss medications. The weekly schedule helps maintain steady medication levels in your body for consistent appetite control and metabolic support throughout the week.

Why an Injection?

Retatrutide is a peptide-based medication. If taken by mouth, stomach acid would break it down before it could be absorbed. A small injection under the skin (subcutaneous) allows the medication to enter the bloodstream effectively and begin working.

Expected Treatment Approach:

• Frequency: One injection once per week, on the same day each week.
• Method: A pre-filled pen device with a small, hidden needle designed for ease and comfort.
• Injection Sites: Typically administered in the abdomen, thigh, or back of the upper arm, rotating sites weekly.
• Titration: Treatment usually starts at a low dose and gradually increases every few weeks to help minimize side effects and allow the body to adjust.

Studied Dose Levels:

• 4 mg: Lower starting dose.
• 9 mg: Mid-level maintenance dose.
• 12 mg: Highest dose studied in clinical trials.

Final dosing recommendations will depend on clinical trial outcomes and official prescribing guidelines if the medication receives regulatory approval.

According to data from Phase 2 and early Phase 3 trials, the once-weekly subcutaneous injection of Retatrutide has shown results that may support multiple aspects of the weight loss journey.

• Significant Weight Loss: In higher-dose groups (12 mg), participants experienced average weight loss approaching 28% of body weight in long-term studies.
• Metabolic Support: Its triple-agonist mechanism targets key metabolic pathways involved in appetite, insulin regulation, and energy expenditure.
• Liver Fat Reduction: Clinical data showed substantial reductions in liver fat levels among participants with fatty liver disease.
• Improved Blood Sugar Control: Many participants with prediabetes returned to normal glucose levels during treatment.
• High-Dose Outcomes: A notable portion of participants achieved weight loss above 30%, a benchmark historically associated with surgical interventions.
• Joint & Inflammation Relief: Participants with obesity-related osteoarthritis reported meaningful reductions in knee pain.
• Insulin Sensitivity: Studies observed improvements in insulin resistance among adults with obesity.
• Appetite Control: Reduced hunger and cravings supported sustainable calorie reduction and long-term weight management.

Results are based on clinical trial data. Retatrutide remains investigational and has not yet received FDA approval.

Like all medications, Retatrutide may cause side effects. According to results from the TRIUMPH-4 trials released in late 2025, the most commonly reported side effects were gastrointestinal in nature.

• Nausea: Reported by approximately 43% of participants on the highest (12 mg) dose.
• Vomiting: Reported by roughly 33% of participants.
• Diarrhea: Reported by about 25% of participants.
• Constipation: Reported by about 21% of participants.

These effects were generally mild to moderate. However, in Phase 3 trials, approximately 18% of participants receiving the highest dose discontinued treatment due to side effects. Some individuals also chose to stop treatment because of rapid weight loss.

Less Common Side Effects:

• Increased Heart Rate: Some participants experienced a small increase in resting heart rate (around 6–7 beats per minute), which stabilized over time.
• Skin Sensitivity (Dysesthesia): Around 20% of people on the 12 mg dose reported mild tingling or skin sensitivity. This was usually not severe enough to require stopping treatment.

Note: Retatrutide is still investigational. Final safety guidance and prescribing recommendations will depend on full clinical trial data and regulatory review.

Retatrutide is not yet approved in the UK. The NHS or private healthcare providers cannot currently prescribe it. Regulatory authorities typically review Phase 3 clinical data before making approval decisions, which may occur in late 2026 or beyond.

• Warning on Scams: Regulatory authorities have issued warnings about illegal online sellers offering unlicensed or counterfeit products. Unregulated medicines may be unsafe and contain unknown substances. Patients should only obtain medications through licensed pharmacies following regulatory approval.
• Authentic Retatrutide: If approved, Retatrutide would only be available through licensed pharmacies with a valid prescription from a qualified healthcare provider. In the meantime, patients seeking treatment may consider approved weight-loss injections such as Wegovy or Mounjaro, or prescription weight loss pills such as Orlistat.

Expected Cost

Eli Lilly has not released official UK pricing for Retatrutide. Based on comparisons with similar once-weekly injectable medications, pricing may be positioned at the higher end of currently available weight-loss treatments.

Final pricing will depend on regulatory approval, manufacturing scale, and market launch strategy. Exact costs will become clearer once the medication receives official authorisation.

For individuals seeking treatment now, currently approved medications remain the only safe and regulated options available in the UK.

Retatrutide and tirzepatide both target hormones involved in appetite and blood sugar control, but there are key differences.

TRIUMPH-5 Trial: A direct head-to-head Phase 3 trial is currently underway comparing Retatrutide and tirzepatide in adults with obesity. Results may be released in late 2026 or 2027.

If you are comparing Retatrutide vs Wegovy in the UK, Wegovy is currently the regulated option available now, while Retatrutide remains in clinical development.

Retatrutide is not currently available on the NHS because it has not yet received regulatory approval in the UK. Before any new medication can be offered by the NHS, it must first be authorised by the MHRA and then assessed for cost-effectiveness by NICE.

• Current status: Investigational medicine in Phase 3 trials.
• NHS availability: Not available at this time.
• Private access: Legitimate access would only be possible after approval and licensed prescribing.

If you are searching for safe alternatives while waiting for Retatrutide, you can review currently approved options on our weight loss treatment hub.