Wegovy Linked to Fivefold Risk of Sudden Sight Loss

Published: 11 March 2026 The English Chronicle Desk The English Chronicle Online – UK News

Patients prescribed the weight‑loss drug Wegovy face nearly five times the risk of sudden sight loss compared with those taking the diabetes medication Ozempic, according to a new study that has raised urgent questions about the safety of high‑dose semaglutide treatments.

The research, published in the British Journal of Ophthalmology, examined adverse event reports submitted to the US Food and Drug Administration between 2017 and 2024. It found a strong association between Wegovy and cases of non‑arteritic anterior ischemic optic neuropathy (Naion)—commonly referred to as “eye strokes.” These events occur when blood flow to the optic nerve is reduced, causing sudden and often permanent vision loss.

Although rare, affecting around one in 10,000 people taking semaglutide, the study’s authors warned of a “potential dose‑dependent safety concern.” Wegovy, marketed by Novo Nordisk, contains the same active ingredient as Ozempic and Rybelsus but at higher doses and in faster‑acting injectable form.

Researchers compared reports linked to three semaglutide products:

Ozempic (up to 2mg weekly injection for type 2 diabetes)
Wegovy (up to 2.4mg weekly injection for obesity—the highest approved dose)
Rybelsus (daily oral tablet for type 2 diabetes)

They also examined tirzepatide (Mounjaro), another GLP‑1 receptor agonist. The findings showed Wegovy had the strongest association with sudden vision loss, while Rybelsus and tirzepatide showed no increased risk.

Dr Edward Margolin, co‑author from the University of Toronto, said Naion was “likely to be a real side‑effect” of semaglutide, adding that faster or more aggressive weight loss could increase the risk.

The study also found men were three times more likely than women to experience Naion while taking Wegovy. Researchers suggested biological differences in optic nerve blood flow may explain the disparity, though further investigation is needed.

The UK Medicines and Healthcare products Regulatory Agency (MHRA) issued a safety update in February, warning prescribers and patients about the risk of Naion. The European Medicines Agency has also updated patient leaflets for Wegovy, Ozempic and Rybelsus to include the condition.

Dr Alison Cave, MHRA’s chief safety officer, stressed that the risk remains “extremely low” but urged vigilance: “As with all medicines, patients and prescribers need to be aware of the symptoms of potential side‑effects, even if the risk is very small, to ensure patients receive the appropriate treatment promptly should they occur.”

Samantha Mann, consultant ophthalmologist at St Thomas’ Hospital in London, cautioned that the study relied on reported side‑effects and could not prove causation. “An increase in this form of optic nerve ‘stroke’ has not been widely observed in routine clinical practice,” she said. “Further studies are needed to clarify if this increased risk is indeed real.”

Novo Nordisk, the Danish pharmaceutical giant behind Wegovy and Ozempic, said patient safety was its “top priority.” A spokesperson confirmed that product leaflets had been updated but insisted the overall benefit‑risk profile of semaglutide remained favourable. “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,” the company said.

Semaglutide drugs have transformed treatment for diabetes and obesity, hailed for their ability to lower blood sugar, reduce appetite and aid weight loss. They have also been linked to reduced risks of heart attack and other health benefits. Demand for Wegovy in particular has surged worldwide, with millions seeking medical help for obesity.

But the new findings highlight the importance of monitoring long‑term safety, especially as higher doses are prescribed for weight loss compared with diabetes management. Experts say the balance between benefits and risks must be carefully assessed, particularly for patients with pre‑existing eye conditions or vascular risk factors.

Doctors are advising patients to watch for warning signs of Naion, including sudden vision loss, blurred vision or dark spots in their field of view. Immediate medical attention is critical, as damage to the optic nerve is often irreversible.

The study underscores both the promise and the risks of breakthrough weight‑loss drugs. While Wegovy offers life‑changing benefits for many patients, its higher dosage may carry rare but serious side‑effects. Regulators, clinicians and manufacturers now face the challenge of ensuring patients are fully informed, closely monitored and supported in making safe treatment decisions.

As demand for semaglutide continues to grow, the debate over its risks and rewards is likely to intensify. For now, the message from experts is clear: vigilance is essential, even when risks are rare.

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