Emerging risk of non-arteritic anterior ischemic optic neuropathy (NAION) with semaglutide: a safety alert for clinicians

Dear Editor, The recent Medicines and Healthcare products Regulatory Agency (MHRA) Drug Safety Update issued on 5 February 2026 has warned of a likely association between semaglutide and non-arteritic anterior ischemic optic neuropathy (NAION)1. NAION is referred to a rare form of ischemic damage to the optic nerve head that typically results in abrupt, painless, unilateral vision loss2. Although the absolute risk appears low in association with semaglutide, with only three UK Yellow Cards reported till August 20251, the profound and often irreversible nature of vision loss demands a proactive and vigilant approach from prescribing clinicians and healthcare systems. We, as healthcare professionals, have seen the significant metabolic benefits of glucagon-like peptide-1 (GLP-1) receptor agonists like semaglutide. However, the increasing use of these drugs in both type 2 diabetes and weight loss suggests that even rare adverse events can potentially affect a significant number of patients in absolute terms. The European Medicines Agency (EMA) and MHRA have estimated the risk of NAION to be about 1 case per 10 000 patient-years of semaglutide exposure. In practical terms, this means one extra case of NAION per 10 000 people treated per year3. This figure becomes much more telling when considering the National Health Service (NHS) data that estimates 10.2 million packs dispensed in the UK from 2020 to 20251. Furthermore, a recent large cohort study published in JAMA Ophthalmology also identified a potential signal, finding that patients with obesity or diabetes treated with semaglutide had a higher risk of NAION compared to those on non-GLP-1 medications4. While there is no clear evidence of causality at this point in time, this collective evidence points to an association and the importance of a thorough investigation. The alert provides clear direction on a practical level. We agree with MHRA and EMA’s advice of sudden vision loss requiring immediate referral to ophthalmology and the potential stoppage of offending drugs. One of the important challenges posed by the update is the rise in private prescribing. Drugs purchased outside of the traditional NHS channels may not be noted in the patient’s care record1. This can lead to a situation where a patient with visual symptoms does not disclose the use of semaglutide. This can potentially delay the key connection to the correct care. Therefore, an important part of the evaluation for any visual problem would be a proactive search for all sources of drugs, including private online clinics or wellness programs. If this warning is not acted upon with specific interventions, we risk preventable vision loss. The consequence of this inaction includes delayed diagnosis for individual patients, which can potentially lead to permanent optic nerve damage. On the other hand, an informed and nuanced response can safeguard patients without causing unnecessary alarm or leading to unjustified discontinuation of a beneficial treatment. The response to this alert is two-fold. First, healthcare professionals must make the specific inquiry for visual symptoms a part of every patient evaluation for semaglutide. Specific emphasis should be placed on particular features of “sudden” and “painless” visual changes. Second, collaboration between regulatory agencies and electronic health record systems must happen to create standardized alerts for patients who are prescribed these medications. This must be done to ensure symptom reporting, which can trigger an immediate referral pathway. The MHRA’s update highlights our collective responsibility in pharmacovigilance. By improving clinical awareness for NAION, we can ensure patient safety without sacrificing the significant therapeutic benefit of semaglutide. Colleagues are encouraged to carefully consider the updated SmPC and PIL when available and to report any suspected cases through the Yellow Card scheme5. Ultimately, the goal is to safeguard patient safety through vigilant monitoring rather than abandoning the significant advances in therapy.