Can Anyone Take Retatrutide? Trial Eligibility

Can anyone take retatrutide? The short answer is no. Retatrutide is an investigational medicine with no marketing authorisation in the UK or elsewhere, meaning it is available only to participants enrolled in authorised clinical trials. It is being studied for the management of obesity and type 2 diabetes and acts on three receptors simultaneously: GIP, GLP-1 and glucagon. This article explains who has been enrolled in trials so far, what exclusion criteria apply, and what side effects have been reported, to help readers understand the current evidence and regulatory position.

What is retatrutide and what is its current status in the UK?

Retatrutide has no UK marketing authorisation and can only be accessed within an authorised clinical trial; it cannot be obtained through a GP, pharmacy or online clinic.

Retatrutide does not hold a marketing authorisation in the UK or anywhere else, meaning it can be prescribed or supplied only within an authorised clinical trial.^[1][2] It is an investigational medicine being studied for the management of obesity and type 2 diabetes. Unlike licensed treatments such as tirzepatide (Mounjaro) or semaglutide (Wegovy), retatrutide cannot be obtained through a GP, a pharmacy or any online clinic outside of a formal research setting. Anyone who encounters retatrutide being sold online should be aware that it is not a licensed product and may be falsified, posing serious safety risks.

Retatrutide is a triple receptor agonist, designed to act on the GIP, GLP-1 and glucagon receptors simultaneously.^[4][5] This mechanism distinguishes it pharmacologically from currently authorised dual or single agonists, though no head-to-head trials with licensed medicines have been conducted, and no direct comparisons can be drawn from existing data. Its development is at an active clinical trial stage, with Phase 3 programmes including the TRANSCEND series under way. No UK marketing authorisation date can be given, as regulatory review has not been completed.

If you are interested in licensed weight-management options, a GP can discuss what is currently available. Access to NHS-funded weight-management medicines depends on local Integrated Care Board (ICB) commissioning and service pathways, so availability may vary by area.^[13]

Who has been enrolled in retatrutide clinical trials so far?

Trials have enrolled adults aged 18 and over with a BMI of 30 kg/m² or above, or 27 kg/m² or above with a weight-related comorbidity, assessed individually by the trial team.

Retatrutide clinical trials have enrolled adults with obesity or overweight accompanied by at least one weight-related comorbidity, as well as adults with type 2 diabetes, depending on the specific trial protocol. In the Phase 2 trial published in the New England Journal of Medicine (Jastreboff et al., 2023), participants were adults aged 18 years and over. Those with a body mass index (BMI) of 30 kg/m² or above were eligible, as were those with a BMI of 27 kg/m² or above provided they had at least one weight-related comorbidity; participants with type 2 diabetes were excluded from that particular study. The TRANSCEND Phase 3 programme has extended enrolment to broader populations, including people with type 2 diabetes.^[7]

Eligibility criteria in clinical trials are carefully defined to protect participant safety and to generate reliable data. Typical inclusion criteria across retatrutide studies have required participants to be adults with documented obesity or overweight, to be weight-stable for a defined period before enrolment, and to be willing and able to follow the trial protocol. Participants are assessed thoroughly at screening, including medical history, laboratory tests and physical examination, before being accepted into a trial.

It is important to understand that meeting the general profile of trial participants does not mean an individual would qualify for a specific study. Each trial has its own protocol, and eligibility is determined by the trial team on a case-by-case basis. Trials are conducted at specific research sites, and participation is not available on request outside of those formal settings. To search for recruiting UK trials, the NIHR 'Be Part of Research' service (bepartofresearch.nihr.ac.uk) provides an authoritative starting point, and a GP can advise further.

Are there people who cannot safely take part in retatrutide trials?

Yes; common exclusion criteria include pregnancy, recent cardiovascular events, history of pancreatitis, and significant renal or hepatic impairment, among others.

Not everyone is eligible to participate in retatrutide clinical trials, and a range of exclusion criteria have been applied across the trial programme to protect participant safety. The following are examples drawn from published retatrutide protocols and should be understood as trial-specific criteria, not as contraindications for any licensed medicine.

Common exclusion criteria in the published Phase 2 trial and the broader TRANSCEND programme have included pregnancy, breastfeeding and planning a pregnancy. Because retatrutide's effects on a developing foetus or infant are not established, women of childbearing potential enrolled in trials are required to use effective contraception throughout participation, reflecting the precautionary approach standard in early-phase research.

Other exclusion criteria reported across retatrutide studies have typically included a recent history of cardiovascular events such as heart attack or stroke, severe gastrointestinal disease, a personal or family history of certain endocrine conditions, significant renal or hepatic impairment, and use of other weight-management medicines or insulin. People with a history of pancreatitis have also generally been excluded, given the class-level signals associated with incretin-based therapies. Psychiatric conditions, active malignancy and certain other chronic illnesses may also preclude participation, depending on the individual trial protocol.

These exclusions mean that the trial populations studied so far do not represent all people who might eventually be considered for this medicine if it were to receive authorisation. The safety and tolerability profile in excluded groups, including older adults, those with complex comorbidities and those who are pregnant or breastfeeding, therefore remains largely unknown. Anyone wishing to find out whether they might be eligible for a retatrutide trial should speak to their GP, who can advise on whether any relevant studies are recruiting in the UK, and the NIHR 'Be Part of Research' service (bepartofresearch.nihr.ac.uk) can be used to search for open studies.

What side effects have trial participants experienced?

The most commonly reported side effects in the Phase 2 trial were gastrointestinal, including nausea, vomiting, diarrhoea and constipation, generally mild to moderate in severity.

In the Phase 2 trial of retatrutide published in the New England Journal of Medicine, the most commonly reported side effects were gastrointestinal in nature, including nausea, vomiting, diarrhoea and constipation. These effects were generally more frequent at higher doses and tended to occur during the dose-escalation phase, with many participants experiencing improvement over time. The majority of gastrointestinal events were described as mild to moderate in severity within the trial report.

Injection-site reactions were also reported by some participants. As with other medicines in the incretin class, there is a concern regarding the pancreas. The MHRA has noted for related authorised medicines that acute pancreatitis has been reported, including post-marketing reports of necrotising pancreatitis and reports with a fatal outcome; no risk magnitude has been established for retatrutide specifically given its investigational status, and participants with a history of pancreatitis have been excluded from trials as a precautionary measure.^[8] Class-associated gallbladder and biliary events have also been observed with related authorised incretin-based medicines and may be relevant to this medicine class more broadly, though the specific profile for retatrutide has not yet been fully characterised.^[9][10]

Because retatrutide is not yet authorised, its full safety profile has not been established across the broader population. The data available come from controlled trial settings with selected participants, and longer-term safety data continue to be collected through the ongoing Phase 3 programme.

If you are enrolled in a retatrutide clinical trial and need urgent or emergency care, tell the treating clinician that you are participating in a clinical trial and provide your study card or study contact details. Suspected side effects should be reported to the trial team under the study protocol. Suspected adverse reactions to medicines can also be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. Anyone experiencing a life-threatening emergency should call 999; for urgent medical advice, NHS 111 is available.

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