Hidden-market sellers promote unlicensed weight-loss drugs through giveaways on WhatsApp and Telegram.
The Guardian found groups advertising retatrutide, an experimental drug without approval.
Posts pressure users with 24-hour deadlines and promise free entry.
Experts warn these tactics pose serious health risks.
One group offered injectable drugs including retatrutide and melanotan II.
None hold UK approval, and experts warn of possible harmful side effects.
UK law allows weight-loss injections only with valid 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.
