What is NAION and what does it feel like?

NAION stands for non-arteritic anterior ischaemic optic neuropathy -- reduced blood flow to the optic nerve. It typically presents as sudden, painless loss or blurring of vision in one eye, often noticed on waking. Some people describe a grey or dark patch (like a curtain) in part of their visual field. It is a medical emergency -- seek urgent care from an ophthalmologist if this happens.

Who is most at risk of NAION on Ozempic?

People with type 2 diabetes appear to carry a higher relative risk, as do people with existing risk factors for reduced optic nerve blood flow, including high blood pressure, high cholesterol, sleep apnoea, and a naturally 'crowded' optic disc (a structural trait your optometrist can check for). People who have already had NAION in one eye are generally advised to discuss GLP-1 use carefully with their doctor, as the other eye may be more vulnerable.

Should I stop taking Ozempic because of the eye risk?

No -- not without speaking to your doctor first. NAION remains rare, and for most people the metabolic and cardiovascular benefits of semaglutide substantially outweigh this risk. However, you should have a baseline eye check if you have diabetes or existing eye conditions, and seek immediate medical attention for any sudden vision change while on the medication. Never stop or start a GLP-1 medication based on general information alone -- always involve your prescribing doctor.

Ozempic and Eye Health: NAION Vision Loss Risk Explained (SA Guide 2026)

Q: Can Ozempic cause blindness?

Ozempic (semaglutide) has been linked to a rare condition called NAION (non-arteritic anterior ischaemic optic neuropathy), which causes sudden, usually permanent, vision loss in one eye. It is rare -- studies estimate roughly 1 in 10,000 users per year, compared to a background rate of about 2 in 10,000 in the general population for related conditions -- but regulators including the EMA have confirmed it as a recognised, if uncommon, side effect. Complete blindness in both eyes from Ozempic would be extremely unusual; NAION typically affects one eye.

By Weight Loss Diets SA | Updated July 2026 | 8 min read

If you've searched "can Ozempic cause blindness," you've probably come across alarming headlines about a condition called NAION. It's a real, medically recognised risk -- but it's also rare, and the full picture is far more reassuring than the scariest headlines suggest. Here's what South Africans using Ozempic, Wegovy, or other semaglutide-based medications actually need to know.

Key point: NAION (non-arteritic anterior ischaemic optic neuropathy) is a rare eye condition involving reduced blood flow to the optic nerve, causing sudden vision loss in one eye. Research published in 2024, along with subsequent regulatory review by the European Medicines Agency, has confirmed an increased -- but still low -- risk in people using semaglutide. It is now listed as a recognised, uncommon side effect.

What Is NAION?

NAION stands for non-arteritic anterior ischaemic optic neuropathy. In plain terms: the small blood vessels supplying the front of the optic nerve (the nerve that carries visual signals from your eye to your brain) become blocked or under-perfused, starving part of the nerve of oxygen.

The result is usually sudden, painless vision loss or blurring in one eye, often first noticed on waking up. Some people describe it as a grey shadow, a dark patch, or a "curtain" covering part of their visual field. Unlike a stroke affecting the brain, NAION affects the eye itself, but it is just as much a medical emergency and needs immediate assessment by an ophthalmologist.

NAION was already a known condition before GLP-1 medications existed -- it occurs in the general population, particularly in people over 50 with cardiovascular risk factors. What changed is that researchers began noticing it more frequently in people taking semaglutide than would be expected by chance.

What Does the Research Actually Show?

A widely reported 2024 study from a major US academic hospital system found that patients prescribed semaglutide had a substantially higher rate of NAION diagnosis over three years compared to similar patients not on the medication -- roughly four times higher in those with type 2 diabetes, and more than seven times higher in those with obesity/overweight without diabetes. Because NAION itself is rare to begin with, even a several-fold increase still translates into a low absolute risk for any individual patient.

Following this and other reports, the European Medicines Agency's safety committee reviewed the evidence and concluded that NAION should be listed as a rare side effect of semaglutide products. Regulators in other markets have issued similar safety communications. This doesn't mean semaglutide is unsafe for the vast majority of users -- it means the risk is now formally acknowledged, monitored, and disclosed, which is exactly how drug safety systems are supposed to work.

Who Is Most at Risk?

Risk Factor	Why It Matters
Type 2 diabetes	Diabetic patients show a notably higher relative risk in the available data
High blood pressure or high cholesterol	Both reduce blood flow efficiency to small vessels, including those feeding the optic nerve
Sleep apnoea	Linked to reduced oxygenation, a known NAION risk factor independent of GLP-1 use
"Crowded" optic disc	A structural trait (small cup-to-disc ratio) your optometrist can identify on a routine exam; it's a well-established NAION risk factor generally
Previous NAION in one eye	The unaffected eye may carry elevated risk; discuss GLP-1 use carefully with your doctor
Smoking	Impairs small-vessel blood flow throughout the body, including the eyes

If none of these apply to you, your individual risk is very low. If one or more do apply -- particularly diabetes -- it's worth a conversation with your doctor before or shortly after starting semaglutide, not as a reason to avoid it outright, but to make an informed decision together.

What Should You Actually Do About It?

Before Starting Ozempic or Wegovy

Mention any existing eye conditions, diabetes, high blood pressure, high cholesterol, or sleep apnoea to your prescribing doctor
If you have diabetes, you should already be having annual diabetic eye screenings in South Africa -- keep these up to date
There's no need for a special pre-treatment eye scan for most healthy adults with no risk factors, but it's a reasonable question to raise with your GP or optometrist

While On the Medication

Know the warning sign: sudden, painless vision loss or blurring in one eye, especially on waking
Treat any sudden vision change as an emergency -- go to a hospital or ophthalmologist immediately, don't wait to see if it improves
Continue routine eye checks, particularly if you're diabetic
Don't stop your medication abruptly based on general anxiety -- speak to your doctor if you're worried

Seek urgent care immediately if: you experience sudden loss or blurring of vision in one eye, a dark patch or "curtain" appearing in part of your visual field, or any sudden change in your eyesight while using semaglutide. Early assessment matters -- go to your nearest eye casualty unit or emergency department without delay.

Putting the Risk in Perspective

It's easy for a headline like "Ozempic linked to blindness" to overshadow the fact that NAION remains uncommon, typically affects only one eye, and the great majority of people using GLP-1 medications for weight loss or diabetes never experience it. Meanwhile, obesity and type 2 diabetes -- the conditions semaglutide is treating -- carry their own well-established risks to eye health, including diabetic retinopathy, a far more common cause of vision loss in South Africa.

The right approach isn't panic, and it isn't dismissal -- it's awareness. Know the symptom, know your personal risk factors, and keep the conversation open with whoever is managing your treatment.

Understand the Full Side-Effect Picture

NAION is one of many things worth knowing before starting a GLP-1 medication. See our complete guide to what to expect.

Ozempic Side Effects: The Complete SA Guide

Bottom Line

NAION is a real but rare side effect now formally recognised by medicines regulators for semaglutide-based drugs like Ozempic and Wegovy. Your individual risk depends heavily on factors like diabetes status, blood pressure, cholesterol, and optic nerve anatomy. For most South Africans, the benefits of GLP-1 treatment for weight and metabolic health continue to substantially outweigh this risk -- but knowing the warning signs, and acting fast if they appear, is essential.

Medical disclaimer: This article is for information only and is not a substitute for professional medical advice. NAION is a serious condition requiring urgent specialist assessment. Always consult your doctor before starting, stopping, or continuing any GLP-1 medication, and seek immediate medical care for any sudden change in vision.