Retatrutide is an investigational injectable medicine being developed by Lilly. It is currently being studied in clinical trials for weight management and type 2 diabetes.

Retatrutide is not approved in the UK and is not available to buy, prescribe or supply outside authorised clinical trials. Do not buy products claiming to contain retatrutide online, from social media or from unregulated suppliers. These products may be illegal or unsafe.

On this page, you can find out more about:

• What retatrutide is used for and how it works
• Why retatrutide is not available in the UK
• Answers to common questions about retatrutide

How does retatrutide work?

Several weight loss injections are GLP-1 receptor agonists, meaning they mimic the hormone glucagon-like peptide-1 (GLP-1) which is usually released by the body when you eat. This activates the receptor for the hormone, leading to:

• Slowing down how quickly food leaves the stomach – staying fuller for longer
• Controlling hunger and food intake

Retatrutide is a triple agonist, meaning it mimics two other hormones including GLP-1:

• Glucose-dependent insulinotropic polypeptide (GIP): A hormone involved in insulin release and metabolism
• Glucagon: A hormone involved in glucose and energy metabolism

This mechanism is being studied to understand whether retatrutide can support weight management when used alongside healthy lifestyle measures. Retatrutide is not approved for use in the UK.

Is retatrutide effective for weight loss?

Retatrutide is still being studied in clinical trials for its effectiveness on assisting weight loss. Some clinical trial results have been reported, but retatrutide remains investigational. It has not been approved for use in the UK, and its licensed indication, dosing, benefits, risks and suitability criteria have not been confirmed through UK regulatory assessment.

Why isn't retatrutide available in the UK?

If you’ve been wondering ‘why can I not buy retatrutide in the UK?’, retatrutide is unavailable in the UK as it is still being studied and cannot be prescribed or supplied outside authorised clinical trials.

Before retatrutide could be made available for routine use in the UK, it would need the appropriate UK medicines authorisation, including assessment by the Medicines and Healthcare products Regulatory Agency (MHRA). The National Institute for Health and Care Excellence (NICE) may also appraise retatrutide to decide whether it should be recommended for NHS use.

There is currently no confirmed date for retatrutide availability in the UK.

Retatrutide side effects

In clinical trials, adverse events have been reported in participants receiving retatrutide. The full safety profile has not yet been confirmed through regulatory assessment.

Reported adverse events have commonly included gastrointestinal symptoms such as:

• Nausea
• Vomiting
• Diarrhoea
• Constipation

This is not a complete safety profile, and retatrutide should not be used outside an authorised clinical trial.