Can Retatrutide Make You Dizzy?

Retatrutide is an investigational triple receptor agonist, acting on GLP-1, GIP and glucagon receptors, that has no marketing authorisation in the UK or elsewhere. Clinical trial data, including the Phase 2 results published in the New England Journal of Medicine in 2023, indicate that dizziness was among the adverse effects reported by participants. This article sets out what is known from published trial data about dizziness and retatrutide, who may be at greater risk, and what to do if symptoms occur. It also explains why purchasing retatrutide outside an authorised clinical trial is unlawful and unsafe.

What Is Retatrutide and What Stage Is It at in the UK?

Retatrutide is an investigational triple receptor agonist (GLP-1, GIP and glucagon) with no UK marketing authorisation; it is available only to participants in authorised clinical trials such as the ongoing Phase 3 TRIUMPH and TRANSCEND programmes.

Retatrutide is an investigational medicine with no marketing authorisation in the UK or anywhere else, meaning it is not licensed for clinical use outside of authorised clinical trials.^[1] It is a triple receptor agonist, acting on glucagon-like peptide-1 (GLP-1), glucose-dependent insulinotropic polypeptide (GIP) and glucagon receptors simultaneously. This triple mechanism distinguishes it pharmacologically from currently licensed medicines, though no authorised head-to-head comparisons exist.

Because retatrutide holds no UK marketing authorisation, the MHRA has not approved it for routine prescribing, and it cannot legally be supplied to patients outside a formal clinical trial setting. The Phase 3 programme, which includes the TRIUMPH trials (evaluating retatrutide for obesity) and the TRANSCEND trials (evaluating it in type 2 diabetes), is ongoing.^[4][5] Some results have been presented at major diabetes and obesity conferences and in peer-reviewed publications, but regulatory review has not yet concluded and no approval timeline can be given.

For people interested in weight management or metabolic health, licensed treatments do exist and can be discussed with a GP. Retatrutide itself remains available only to participants enrolled in an authorised clinical trial, and no other legitimate route of access currently exists in the UK.

What side effects were reported in retatrutide clinical trials?

The Phase 2 trial (NEJM, 2023) reported nausea, vomiting, diarrhoea, constipation and dizziness as common adverse effects; the full safety profile remains under investigation in Phase 3 trials.

Dizziness was among the adverse effects reported by participants in retatrutide clinical trials, alongside a broader pattern of gastrointestinal symptoms consistent with the GLP-1 receptor agonist class. In the Phase 2 trial published in the New England Journal of Medicine (2023), the most commonly reported side effects included nausea, vomiting, diarrhoea and constipation. Dizziness was also noted during the trial period; whether it clustered specifically during dose escalation phases has not been confirmed in published data, and this should be regarded as a hypothesis based on the known pharmacology of the class rather than an established finding for retatrutide specifically.

The gastrointestinal effects are thought to relate primarily to the GLP-1 component of retatrutide's mechanism, which slows gastric emptying and influences appetite-regulating centres in the brain.^[6][7] Dizziness may arise through several plausible pathways, including reduced food and fluid intake leading to dehydration, a drop in blood pressure (particularly postural hypotension), or a direct central nervous system effect. These mechanistic explanations are hypotheses; the relative contribution of each has not been definitively established in published trial data for retatrutide.

Other adverse effects reported in trials included injection-site reactions, fatigue and, in participants with type 2 diabetes, changes in glycaemic control. Acute pancreatitis has been reported in the GLP-1 receptor agonist class more broadly, including post-marketing reports of necrotising pancreatitis and reports with a fatal outcome; the UK SmPCs for licensed medicines in this class note these reports without quantifying the risk magnitude.^[10] As retatrutide is still investigational, its full safety profile has not been established. Results from the ongoing Phase 3 TRIUMPH and TRANSCEND programmes, as they are published, will provide a more complete picture of the safety and tolerability of retatrutide.

Who may be more at risk of dizziness during trials?

People taking antihypertensives, insulin or sulphonylureas, and older adults with lower baseline body weight, may be at greater risk of dizziness based on class-level pharmacology, though retatrutide-specific subgroup data are not yet published.

Certain groups of trial participants may be more likely to experience dizziness during retatrutide studies, based on the known pharmacology of the drug class and the characteristics of people enrolled. These observations are clinical considerations drawn from class-level evidence rather than established findings specific to retatrutide, and should be interpreted accordingly.

Individuals who reduce their caloric intake substantially, particularly early in dose escalation, may experience dehydration or electrolyte imbalance, both of which can contribute to light-headedness and dizziness. People taking antihypertensive medicines or those with a tendency towards low blood pressure may be at greater risk of postural hypotension, where blood pressure drops on standing, causing a brief sensation of dizziness or unsteadiness.^[6] Participants with type 2 diabetes who are also taking insulin or sulphonylureas may experience hypoglycaemia, which can itself cause dizziness, sweating and confusion.^[2][3]

Older adults and those with a lower body weight at baseline may also be more susceptible to the haemodynamic effects of reduced intake and altered fluid balance, though subgroup data specific to retatrutide are not yet published. Trial protocols typically include monitoring for these effects, and participants are advised to report symptoms promptly to the trial team.

If you are enrolled in a clinical trial and experience dizziness or any other concerning symptom, contact your trial team in the first instance. If you need urgent or emergency care, tell the clinician treating you that you are participating in a clinical trial and show your trial participant card or documentation, so that the trial team can be informed and any interactions with trial procedures can be considered.

Anyone experiencing persistent or severe dizziness outside a trial context should contact their GP, or call NHS 111 for urgent advice if symptoms are more acute.

Is it safe to buy retatrutide online if it is not yet licensed?

Retatrutide cannot be legally purchased online in the UK; any product sold under this name is unregulated, may be falsified or contaminated, and carries serious safety risks with no legal recourse.

Retatrutide cannot be legally purchased online in the UK because it holds no marketing authorisation, and any product sold online under this name is not a licensed medicine. Purchasing such products carries serious risks: the substance may be falsified, contaminated, incorrectly dosed or entirely different from what is claimed on the label. There is no regulatory oversight of these products, no quality assurance and no recourse if harm occurs.

The MHRA has warned about the dangers of buying unlicensed medicines online, including falsified injectable products.^[11] Its published guidance on buying medicines online (available at gov.uk/guidance/buying-medicines-online) sets out how to identify legitimate online pharmacies and the risks associated with unregulated sources. Because retatrutide is still investigational, even its full safety profile in controlled trial conditions is not yet established. Using an unverified product of unknown composition compounds that uncertainty considerably.

If you believe you have experienced an adverse effect from a product purchased online, seek medical advice from your GP. For life-threatening symptoms, call 999 or go to your nearest accident and emergency department. Suspected adverse reactions to any medicine, including those obtained outside licensed channels, can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Anyone seeking weight management support should speak to their GP about licensed options that have been assessed for safety and efficacy by the MHRA and evaluated by NICE.^[16][17] Legitimate access to retatrutide remains restricted to participants in authorised clinical trials, and no other supply route is currently lawful or safe in the UK.

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