The first Instagram, TikTok and Facebook posts by members of the public promoting weight-loss jabs have been banned by the advertising regulator.

The posts used discount codes and referral links to advertise the injections, including Mounjaro, for the online pharmacies Voy, Zava, MedExpress and the online prescribing service UK Meds Direct, the Advertising Standards Authority (ASA) said.

Weight-loss injections are a prescription-only medicine and therefore cannot be advertised to the public.

Affiliate or referral schemes typically allow individuals to share links or discount codes and give them a reward or other benefit if someone else uses them.

The ASA warned that, in practice, this could mean members of the public promoting prescription-only medicines to friends, family, followers and the public, sometimes without realising that their posts may be ads or that strict rules apply to them.

The regulator said its rulings made clear that both brands and individuals are responsible for sticking to advertising rules, and that posts that include affiliate or referral schemes can still count as ads, even if they appear on personal social media accounts.

The banned posts promoted the medicines by naming them directly, using related hashtags, showing images of injection pens or encouraging followers to start their own weight-loss ‘journey’, alongside offering discounts or incentives.

The ASA ruled that they were advertising prescription-only medicines because they were public posts.

It also found that although the companies had not directly asked for the posts to be made, they did control how their affiliate and referral schemes worked.

This meant they were also responsible for making sure the advertising rules were followed.

The ASA warned that weight-loss prescription drugs were powerful medicines that should be used only under the supervision of a qualified medical professional, adding: “Promoting them irresponsibly and illegally can put people at serious risk, which is why this is a priority area for us.”

Catherine Drewett, investigations manager at the ASA, said: “Today’s rulings send a clear message that affiliate marketing is not a loophole and that promoting prescription medicines through social media, whether as a brand, influencer or customer, is against the law and our rules.

“We’ll continue take swift action in this area to make sure the rules are followed and that people are protected from harmful and irresponsible ads.”

A spokeswoman for Voy said: “The posts referenced in the ruling were made independently by customers of our service back in 2024 as part of a referral scheme for our weight-loss programme.

“These posts were first brought to our attention in June 2025, and since we have strengthened our controls around referral activity and influencer engagement. Clinical decisions — including whether medication is suitable — are always made privately between patients and qualified clinicians, and no influencers or referrers play any role in diagnosis, prescribing or medical advice.”

Zava said: “We are committed to being a responsible and compliant healthcare organisation that follows regulation and guidance from the ASA.

“While we were disappointed by the ruling, we note that we had no commercial or affiliate relationship with the social media users who created the posts in question, and as a business we do not have oversight or control over content shared independently by members of the public on their own social media channels.”

Julian Beach, interim executive director of healthcare quality and access at the Medicines and Healthcare products Regulatory Agency (MHRA), said: “We welcome today’s rulings from the ASA. Prescription-only weight-loss medicines carry real risks and must only be prescribed following a proper clinical assessment.

“The promotion of these medicines through affiliate schemes and social media circumvents important safeguards that exist to protect patients.

“We will continue to work closely with the ASA and General Pharmaceutical Council (GPhC) to take action against those who break the rules and put people’s health at risk.”

Dionne Spence, chief enforcement officer at the GPhC, said: “These rulings from the ASA send a clear message that online providers are responsible for making sure that advertising rules are followed, including when working with individuals through affiliate or referral schemes.

“We welcome the action taken by the ASA and we have taken action to follow up with the pharmacies registered with us.”