Hidden sellers promote unlicensed weight-loss drugs through WhatsApp and Telegram giveaways.
They offer injectable medicines as prizes to attract users quickly.
The Guardian found groups advertising retatrutide, an unapproved experimental drug.
Posts pressure users with 24-hour entry deadlines.
Experts warn these promotions pose serious health risks.
They say marketers misuse aggressive tactics for unlicensed medicines.
One group offered retatrutide, Glow pens, and melanotan II as prizes.
None of these injectable products hold UK approval.
UK law allows weight-loss injections only with prescriptions.
Unapproved drugs cannot be legally sold or advertised.
Another seller disguises drug sales as fitness coaching.
Platform owners say they ban illegal drug sales.
