Ozempic and other medicines containing semaglutide have been associated with a rare eye condition that can cause sudden and potentially permanent loss of vision, usually in one eye.
The condition is called non-arteritic anterior ischemic optic neuropathy, commonly shortened to NAION. It occurs when blood flow to part of the optic nerve is interrupted, damaging the nerve that carries visual information from the eye to the brain.
Evidence of a possible link has grown through patient reports and several large observational studies. European regulators have now concluded that NAION should be listed as a very rare side effect of semaglutide medicines, including Ozempic, Wegovy and Rybelsus.
What Is NAION?
NAION is a type of optic-nerve injury that usually causes sudden, painless vision loss. It commonly affects one eye at a time and is often first noticed after waking in the morning.
A person may experience blurred or darkened vision, loss of part of the visual field, reduced color perception or a shadow across the affected eye. The amount of vision lost can vary, but the damage may be permanent because injured optic-nerve tissue does not reliably recover.
The condition differs from a retinal detachment or stroke inside the brain, although all sudden changes in vision should be treated as a medical emergency.
Risk factors for NAION already include diabetes, high blood pressure, cardiovascular disease, obstructive sleep apnea and certain anatomical features of the optic nerve. Many people prescribed semaglutide have some of these underlying risk factors, which makes it challenging to separate the effects of the medicine from the effects of their existing health conditions.
Why Ozempic Has Been Connected to Vision Loss
Concern increased after researchers at a specialist neuro-ophthalmology center observed an unexpected number of NAION cases among patients taking semaglutide.
A 2024 study published in JAMA Ophthalmology examined patients with type 2 diabetes or overweight and obesity who had been prescribed semaglutide. The researchers found an association between semaglutide use and a higher rate of NAION compared with patients receiving other treatments.
Because the study was observational and based on patients attending a specialist eye center, it could not prove that semaglutide caused the condition. Its findings nevertheless prompted further research and regulatory reviews.
A later analysis involving a broader US population also suggested a modest increase in NAION risk among people with type 2 diabetes who used semaglutide. The estimated increase was smaller than that reported in the original specialist-clinic study, reinforcing the view that the condition is serious but uncommon.
A subsequent systematic review estimated that NAION occurred at a rate of approximately 26.7 cases per 100,000 person-years among semaglutide users with diabetes, compared with 18.9 cases per 100,000 person-years among people not using the medication. These figures indicate a small absolute risk even where an association is present.
European Regulators Recognized NAION as a Very Rare Side Effect
In June 2025, the European Medicines Agency’s Pharmacovigilance Risk Assessment Committee completed its review of the available clinical-trial, observational and post-marketing evidence.
The committee concluded that NAION is a very rare side effect of semaglutide, meaning it may affect up to one person in every 10,000 taking the medication. It recommended updating the European product information for Ozempic, Wegovy and Rybelsus to include the risk.
The updated European information advises patients to contact a doctor immediately if they experience sudden vision loss or rapidly worsening eyesight. It also states that semaglutide treatment should be discontinued if an ophthalmological examination confirms NAION.
The official safety conclusion can be read through the European Medicines Agency.
Does Ozempic Definitely Cause Vision Loss?
The European regulatory review concluded that the available evidence was sufficient to establish a causal relationship between semaglutide and NAION for medicine-labeling purposes. However, important scientific questions remain about which patients are most vulnerable and how the medicine might contribute to optic-nerve damage.
Most of the supporting research has been observational. Such studies can reveal associations across large groups of patients, but they may also be affected by differences in diabetes severity, weight, cardiovascular health, sleep apnea, access to eye care and other factors.
Research findings have not been completely consistent. Some observational studies identified an increased risk, while others did not. A systematic review of randomized trials did not find a general increase in eye disorders or diabetic retinopathy associated with semaglutide, although rare conditions such as NAION can be difficult to detect in clinical trials because relatively few cases occur.
The most accurate conclusion is that NAION appears to be a genuine but very rare risk rather than a common effect of Ozempic.
How Semaglutide Might Affect the Optic Nerve
Researchers have not established the exact mechanism connecting semaglutide with NAION.
One possibility is that rapid changes in blood sugar, blood pressure or fluid balance could temporarily affect blood flow to the optic nerve in susceptible people. Semaglutide may also produce substantial metabolic changes, particularly during the first months of treatment or following a dose increase.
NAION often develops when blood supply to the optic-nerve head falls below a critical level. This may happen overnight, when blood pressure naturally decreases. People with sleep apnea, vascular disease or tightly packed optic nerves may have less ability to tolerate further reductions in blood flow.
These proposed explanations remain under investigation and should not be treated as confirmed mechanisms.
Vision Changes Can Have Other Causes
Not every visual problem experienced while using Ozempic is NAION.
People with diabetes can develop diabetic retinopathy, cataracts, glaucoma, retinal blood-vessel problems and temporary blurred vision caused by changing glucose levels. Semaglutide product information has previously warned that rapid improvement in blood-sugar control may temporarily worsen diabetic-retinopathy complications in some patients who already have the condition.
NAION typically produces sudden, painless and noticeable vision loss. Temporary mild blurring that changes throughout the day may have a different cause, but it should still be discussed with a healthcare professional.
Only an urgent eye examination can determine whether the optic nerve, retina or another part of the visual system has been affected.
Warning Signs That Require Immediate Attention
A person taking Ozempic, Wegovy or Rybelsus should seek urgent medical assessment if vision suddenly becomes dark, blurred or missing in one eye.
Other warning signs include a shadow or curtain over part of the visual field, difficulty seeing objects above or below the normal line of sight, sudden changes in color perception or eyesight that worsens rapidly without pain.
Patients should not wait for a routine appointment to see whether sudden vision loss improves. Rapid examination by an ophthalmologist or emergency department is important because several eye conditions that cause similar symptoms require immediate treatment.
Even though there is currently no consistently effective treatment that restores vision lost through NAION, an urgent diagnosis can rule out other emergencies and help protect the unaffected eye.
Should Patients Stop Taking Ozempic?
Patients should not stop a prescribed semaglutide medicine without speaking with their clinician unless they are experiencing an urgent reaction and have been instructed to discontinue it.
Ozempic can provide major benefits for blood-sugar control and may reduce cardiovascular and kidney complications in appropriately selected patients. Wegovy can support clinically significant weight loss and reduce certain cardiovascular risks in people with obesity or overweight.
For most patients, the likelihood of NAION remains very low. The decision to continue treatment should consider the person’s diabetes control, cardiovascular risk, weight-management needs, existing eye disease and possible NAION risk factors.
Patients who have previously experienced NAION in either eye should discuss that history with the clinician prescribing semaglutide. They may also benefit from an ophthalmological evaluation before starting or continuing treatment.
What Current Evidence Means for Patients
The increasing number of reports does not mean that sudden blindness is becoming a common consequence of Ozempic use. Growing awareness, wider use of semaglutide and improved reporting can all contribute to more cases being identified.
The evidence does indicate that patients and prescribers should take sudden vision changes seriously. European regulators now classify NAION as a very rare side effect, and continuing studies are helping researchers estimate the risk more precisely.
People taking semaglutide should understand the warning symptoms without becoming unnecessarily alarmed. Sudden vision loss or rapidly worsening eyesight requires immediate medical attention, while routine treatment decisions should be made together with a qualified healthcare professional.
