Wegovy users have five times the risk of experiencing permanent sight loss linked to weight loss jabs than those taking other GLP-1 medications, a concerning new study has found.
Semaglutide – the powerful ingredient behind the blockbuster jabs – has long been hailed as a monumental breakthrough on the war against obesity.
But according to a study published in the British Journal of Ophthalmology, semaglutide in any formulation could put users at an increased risk of ischemic optic neuropathy (ION).
Wegovy – manufactured by Novo Norsk – was found to carry the highest risk, and men had a three times greater risk than women.
The condition, also known as an ‘eye stroke’, occurs when blood flow to the optic nerve is restricted, depriving it of oxygen and causing sudden and usually permanent vision loss.
Experts have previously disagreed on how common the problem is among weight loss drug users, with manufacturers at the time saying that blindness was not ‘a known adverse drug reaction.’
But, to pinpoint whether the risk may be associated with specific weight loss medications, Canadian experts analysed reports of harmful side effects associated with the drugs submitted to the US Food and Drug Administration (FDA), between December 2017 and 2024.
They said: ‘This study provides the first evidence of a formulation-and-dose-dependent ION risk, with the strongest association observed for Wegovy.
The condition, known as an ‘eye stroke’, occurs when the vessels supplying blood to the optic nerve become blocked
‘These findings highlight a potential dose-dependent safety concern that warrants urgent prospective evaluation to guide prescribing and regulatory process.’
The researchers looked at eye-strokes associated with up to 2mg of Ozempic for type 2 diabetes, 2.4mg of Wegovy for obesity and a daily oral pill prescribed for type 2 diabetes, called Rybelsus. All of these drugs contain semaglutide as their active ingredient.
They also looked at reports of adverse side-effects linked with a weekly injection of tirzepatide, sold under the brand name Mounjaro, for type 2 diabetes.
Out of 30,668,520 reports, over 31,000 involved semaglutide, with users aged around 56, the majority of whom were female.
Despite Ozempic generating around seven times more reports of harmful side effects than Wegovy – owing to its earlier approval – ION was 75 times more likely to be reported by people taking Wegovy.
No link was found between Rybelsus and sudden vision loss.
The researchers forwarded a number of reasons for this, suggesting that higher doses of Wegovy may reduce blood flow to the optic nerve by lowering blood pressure.
Rybelsus, on the other hand, is absorbed much more slowly, minimising the risk of this sudden drop in blood pressure.
They concluded: ‘These findings add to an emerging body of growing literature reporting ocular complications with anti-obesity medications, which warrants further scrutiny and urgent clarification for ophthalmologists.’
The researchers added that this is of particular importance, given the growing use of weight loss jabs in children, which could significantly increase their risk of vision problems later in life.
It comes following a warning issued by the Medicine’s and Healthcare products Regulatory Agency (MHRA) last month, which urged weight loss jab users to report any changes in their vision to a medical professional.
It said: ‘Patients taking semaglutide who notice a sudden change in their eyesight, such as sudden impairment to their vision, or if eyesight gets worse very quickly in one or both eyes, should urgently attend eye casualty or A&E.’
The drug watchdog added that Wegovy prescriptions will now come with a safety warning about the risk of blindness.
Since semaglutide was authorised in the UK in 2018, there have been three suspected reports of eye-stroke, according to the MHRA.
In the past five years there has been an approximate 10.2millions prescriptions of the drug handed out.
Figures released by UCL at the start of the year estimate that up to 1.6million people in Britain have used weight-loss drugs like Wegovy or Mounjaro in the past year.
The vast majority of these users are accessing the medication privately rather than through the NHS, with usage doubling between 2024 and 2025.
There are currently no treatments for ION, which is thought to affect around one in 10,000 people, and vision often does not improve.
Robbie Williams has previously spoken out about the risk, stating he was worried weight loss jabs were ‘making him blind’
Novo Nordisk, the developer of semaglutide, is currently facing several lawsuits in the US from patients who claim the drug robbed them off their sight.
In response Novo Nordisk said: ‘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.
‘Based on the totality of evidence we concluded that the data did not suggest a reasonable possibility of a causal relationship between semaglutide and ION and Novo Nordisk believes that the benefit-risk profile of semaglutide remains favorable.’
It added the EU patient leaflets and Summary of Product Characteristics for Wegovy, Ozempic and Rybelsus tablets – which all contain semaglutide – have been updated to include the risk.
