Hidden-market sellers promote unlicensed weight-loss drugs through WhatsApp and Telegram giveaways.
They offer injectable medicines as competition prizes.
The Guardian found groups advertising retatrutide, an experimental drug without approval anywhere.
Posts pressure users to enter within 24 hours.
Experts warn these promotions pose serious health risks.
They say marketers misuse aggressive tactics to sell unlicensed medicines.
UK law restricts weight-loss injections to prescription-only supply.
Platforms including Telegram and Meta say they ban illegal drug sales.
