After semaglutide and Mounjaro failed, woman turns to black‑market retatrutide; health experts warn

A 29-year-old woman in Dartford, Kent, who said she had seen limited benefit from semaglutide and tirzepatide, told reporters she turned to an online seller for retatrutide — an investigational weight‑loss drug — after seeing recommendations on social media. She described rapid weight loss and lower cost compared with prescription options, but acknowledged she was aware of the risks of using an unregulated product.

The woman, who asked to be identified only as Erin, said she first tried semaglutide — the active ingredient in Ozempic and Wegovy — after deciding to focus on weight loss in January following a change in family circumstances. At about 5ft 8in and nearly 15 stone, she said her body mass index placed her in the obese range. After three months on a semaglutide regimen purchased online, she said her weight had not changed. She then tried tirzepatide, marketed as Mounjaro, for five months after obtaining doses through a friend, and again saw little effect.

Erin said she started seeing posts on TikTok touting retatrutide, a drug classed by researchers as a multi‑agonist designed to suppress appetite and alter metabolism. Those posts, she said, described weight changes surpassing what users reported with approved medicines. She said she purchased the product online, began injecting it herself and saw what she described as "staggering" weight loss within weeks.

Health professionals and regulators have repeatedly warned that buying medicines outside licensed channels carries significant risks. Clinicians and public health experts say unregulated products may contain incorrect dosages, contaminants or completely different active ingredients, and that patients who use them lack the routine medical monitoring that accompanies prescription treatment.

Retatrutide is an investigational compound that has been the subject of clinical trials; it is not approved for general medical use. Approved GLP‑1 receptor agonists such as semaglutide and the dual GIP/GLP‑1 agonist tirzepatide are prescribed with medical supervision to manage obesity and metabolic conditions. Trials of newer, multi‑agonist compounds have reported marked weight loss in early studies, but they remain under evaluation for safety, tolerability and long‑term effects.

Doctors caution that even approved antiobesity medications have side effects that require oversight. Commonly reported adverse effects include nausea, vomiting, diarrhoea and changes in appetite. More serious but less common risks can include pancreatitis, gallbladder disease and potential effects on thyroid tissue observed in animal studies. The safety profile of experimental formulations obtained outside regulated trials is unknown.

Experts say social media has amplified demand for novel weight‑loss therapies, with short videos and personal testimonials encouraging some people to seek out alternatives when they do not respond to approved treatments. Cost and limited access through clinical practices and pharmacies are also factors that drive people to online markets, clinicians say.

Regulators and professional bodies advise that patients seeking medical treatment for weight loss consult licensed prescribers and obtain medications through authorised pharmacies or within clinical trials, where dosing, side effects and interactions can be monitored. They warn against self-administration of injectable medicines obtained from unverified sources.

Public‑health authorities have also expressed concern that illicit supplies may undermine ongoing clinical research and patient safety monitoring. Trials of investigational agents like retatrutide collect detailed safety data, but illicit use circumvents those safeguards and may expose users to unknown harms.

The woman said she understood the risks but felt compelled to act after months without progress and the pressure of changing family responsibilities. Her experience highlights tensions between patient demand for effective weight‑loss options and the structured processes regulators require to ensure treatments are safe and effective for the broader population.

Clinicians emphasise that treatment for obesity commonly involves a combination of medical, behavioural and lifestyle approaches, and that some people may not respond to a single drug. For those who do not see benefit from one therapy, doctors can consider alternative approved options, dose adjustments or enrolment in approved clinical trials, all under medical supervision.

Authorities encourage anyone who has purchased or used a medicine from an unlicensed source to inform their health professional and to seek immediate care for concerning symptoms. They also urge people to report suspicious online drug sellers to relevant regulatory bodies so that supply chains for potentially dangerous products can be investigated.