The advertising regulator has banned early posts on Instagram, TikTok and Facebook by members of the public promoting weight loss injections.
The posts used discount codes and referral links to advertise injections, including Mounjaro, for online pharmacies Voy, Zava, MedExpress and online prescription service UK Meds Direct, the Advertising Standards Authority (ASA) said.
Weight loss injections are medications that are sold only by prescription and therefore cannot be advertised to the public.
Affiliate or referral schemes usually allow people 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 general public, sometimes without realizing that their posts may be advertisements or that strict rules apply to them.
The regulator said its rulings made clear that both brands and individuals are responsible for complying with 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 drugs by directly naming them, using related hashtags, showing images of injection pens, or encouraging followers to start their own weight loss “journey,” as well as offering discounts or incentives.
The ASA ruled that they were advertising prescription drugs because they were public publications.
It also found that although the companies had not directly requested the posts to be published, they did control how their affiliate and referral schemes worked.
This meant that they were also responsible for ensuring that advertising standards were met.
The ASA warned that prescription weight loss drugs were powerful drugs that should only be used under the supervision of a qualified medical professional, adding: “Promoting them irresponsibly and illegally can put people at serious risk, so 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 will continue to take swift action in this area to make sure the rules are followed and people are protected from harmful and irresponsible ads.”
A Voy spokeswoman said: “The posts referred to in the ruling were made independently by customers of our service in 2024 as part of a referral plan for our weight loss program.
“These posts first came to our attention in June 2025, and we have since strengthened our controls around referral activity and influencer involvement. Clinical decisions, including whether medication is appropriate, are always made privately between patients and qualified clinicians, and no influencer or referrer plays any role in diagnosis, prescribing or medical advice.”
Zava said: “We are committed to being a responsible healthcare organization that complies with ASA regulations and guidelines.
“While we were disappointed by the ruling, we noted that we had no business or affiliation relationship with the social media users who created the posts in question and, as a company, we have no oversight or control over content independently shared by members of the public on their own social media channels.”
Julian Beach, acting executive director of healthcare quality and access at the Medicines and Healthcare products Regulatory Agency (MHRA), said: “We welcome today's decisions by the ASA. Prescription-only weight loss medicines carry real risks and should only be prescribed after appropriate clinical assessment.
“The promotion of these medications through affiliate schemes and social media circumvents important safeguards that exist to protect patients.
“We will continue to work closely with the ASA and the General Pharmaceutical Council (GPhC) to take action against those who break the rules and put people's health at risk.”
Dionne Spence, GPhC enforcement director, said: “These ASA rulings send a clear message that online providers are responsible for ensuring advertising rules are followed, even when working with people through affiliate or referral schemes.
“We welcome the actions taken by the ASA and have taken steps to follow up with pharmacies registered with us.”
