Sight loss risk four times greater for Wegovy users compared to Ozempic

The risk of sudden vision loss is four times higher for users of Wegovy compared to those using Ozempic, according to a new large-scale study.

The study, published in the British Journal of Ophthalmology, found that patients taking Wegovy for weight loss were at greater risk of developing non-arteritic anterior ischemic optic neuropathy (NAION) – a condition that causes sudden, painless loss of vision – than patients taking Ozempic were.

The authors found no increased risk with Rybelsus tablets – which also contain semaglutide – or tirzepatide.

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Although NAION only affects around one in 10,000 people who take semaglutide, the study said these fundings revealed ‘a potential dose-dependent safety concern’ that requires ‘urgent prospective evaluation to guide prescribing and regulatory policy’.

The authors said that the ‘high dose’ of Wegovy and that the fact injections were faster acting could explain why the risk was higher, although ‘no direct clinical link has been established’. In contrast, the limited absorption and slower uptake of Rybelsus tablets probably explained the absence of a detectable link, they said.

To conduct the study, Canadian researchers examined reports of side-effects submitted to the US medicines regulator, the Food and Drug Administration (FDA), through its adverse event reporting system between December 2017 and December 2024.

They compared over 30 million reports (30,668,520) of NAION associated with up to 2mg of weekly Ozempic injections for type 2 diabetes; up to 2.4mg of weekly Wegovy injections for obesity and a daily Rybelsus tablet for type 2 diabetes. They also examined reported side effects of tirzepatide (Mounjaro).

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This new study comes after the Medicines and Healthcare products Regulatory Agency (MHRA) added the ‘very rare’ risk of NAOIN to the product information of semaglutide in February 2026.

The MHRA’s chief safety officer, Dr Alison Cave, said at the time that while the potential risk of NAION for patients prescribed semaglutide was ‘extremely small’, it was important that patients and healthcare professionals were alert to the associated symptoms.

A spokesperson for Novo Nordisk – manufacturer or Wegovy, Ozempic and Rybelsus – said in response to the new study: ‘Patient safety is our top priority, and we take any reports about adverse events from the use of our medicines very seriously. We work closely with authorities and regulatory bodies from around the world to continuously monitor the safety profile of our products.

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‘Based on the totality of evidence we concluded that the data did not suggest a reasonable possibility of a causal relationship between semaglutide and NAION and Novo Nordisk believes that the benefit-risk profile of semaglutide remains favourable.’

The product information for all GLP-1 and dual GLP-1/GIP receptor agonists was also recently updated to highlight the risk of severe acute pancreatitis, including rare reports of necrotising and fatal pancreatitis.