The US Food and Drug Administration (FDA) has ruled that manufacturers of popular diabetes and weight-loss medicines, including Ozempic, Wegovy, Mounjaro and Zepbound, should add warnings about a rare eye condition that can cause permanent vision loss.
The safety update concerns non-arteritic anterior ischaemic optic neuropathy (NAION), a condition caused by reduced blood flow to the front part of the optic nerve. It can lead to sudden, painless loss of vision in one eye, although its underlying cause is not fully understood.
The FDA said it was requiring manufacturers of all glucagon-like peptide-1 receptor agonist (GLP-1 RA) medicines to include information about the potential increased risk in the 'Warnings and Precautions' section of their product labels.
The decision follows a review of clinical trial data, animal studies, post-marketing reports and observational research. The agency said cases of NAION had been reported across all currently marketed GLP-1 RA products.
The medicines are widely used to manage type 2 diabetes and obesity. Certain products also have approved uses relating to cardiovascular risk, kidney disease, obstructive sleep apnoea and metabolic dysfunction-associated steatohepatitis (MASH).
Pharmacy Business previously reported on the MHRA's warning over semaglutide and the rare eye condition, as well as research examining the possible association between semaglutide and vision loss.
The latest FDA advice applies more broadly across the GLP-1 class, reinforcing the need for patients and healthcare professionals to remain alert to potential adverse effects while weighing the benefits and risks of treatment.
How significant is the potential risk?
The FDA's analysis of 126 randomised controlled clinical trials involving 134,253 participants identified 15 probable cases of NAION.
Of these, 10 occurred among people taking GLP-1 medicines and five among those receiving comparator treatments. No cases were identified among participants taking other non-GLP-1 glucose-lowering medicines.
The incidence rate was 6.4 cases per 100,000 person-years among GLP-1 users, compared with 3.8 cases per 100,000 person-years among people receiving a placebo or other comparator treatment.
The FDA also examined real-world data from adults with type 2 diabetes who started GLP-1 medicines or other commonly prescribed diabetes treatments between 2019 and 2024.
This analysis found NAION incidence rates of 30 to 32 cases per 100,000 person-years among GLP-1 users, compared with 31 among those taking sodium-glucose cotransporter-2 (SGLT-2) inhibitors and 26 among patients receiving dipeptidyl peptidase-4 (DPP-4) inhibitors.
The agency did not find a statistically significant increase in risk among GLP-1 users compared with SGLT-2 inhibitor users. However, it identified an increased risk compared with patients taking DPP-4 inhibitors.
The findings do not establish that GLP-1 medicines directly cause NAION. The FDA said risk factors for the eye condition often overlap with health conditions commonly found among people prescribed these medicines, making individual cases difficult to interpret.
What should patients and healthcare professionals know?
Symptoms of NAION include sudden, painless loss of vision in one eye, which some people may first notice upon waking. Other warning signs include blurred or hazy vision, blind spots, tunnel vision, distorted colours and reduced sharpness of central vision.
The FDA has advised patients to contact their healthcare professional immediately if they experience these symptoms. Anyone suspected of having NAION should be referred promptly to an ophthalmologist for assessment.
People with a history of NAION face an increased risk of recurrence, while those who have experienced the condition in one eye may be at greater risk of developing it in the other.
Other potential risk factors include diabetes, high blood pressure, smoking, sleep apnoea, anaemia and kidney disease.
Healthcare professionals have been advised to discuss the potential risk with patients and consider discontinuing GLP-1 treatment if NAION develops, unless the benefits of continuing clearly outweigh the risks. Patients who experience an episode should discuss their treatment with their prescribing clinician rather than stopping medication independently.
The FDA began investigating the issue after a 2024 study raised concerns about a possible association between semaglutide and NAION. Semaglutide is the active ingredient in Ozempic, Wegovy and Rybelsus.
Novo Nordisk, which manufactures the three medicines, said it continued to believe that the available data did not establish a cause-and-effect relationship and remained confident in the benefit-risk profile of its GLP-1 medicines.
Eli Lilly, which produces Mounjaro and Zepbound, said the FDA's communication applied to all medicines with GLP-1 receptor agonist activity and did not refer to findings specific to its products. The company said it was evaluating the update.
The FDA's decision adds to regulatory scrutiny of the rapidly expanding weight-loss and diabetes drug market. In the UK, the Medicines and Healthcare products Regulatory Agency (MHRA) had already updated semaglutide product information to include the rare risk of NAION earlier in 2026.
The latest FDA advice applies more broadly across the GLP-1 class, reinforcing the need for patients and healthcare professionals to remain alert to potential adverse effects while weighing the benefits and risks of treatment.
