Could Semaglutide Cause Vision Loss? What Regulatory Warnings and Scientific Evidence Tell Us

Medications used to treat obesity and diabetes are being investigated for a possible association with a rare optic nerve disorder. Learn what the scientific evidence shows, how significant the risks are, and how to use these treatments safely.

Semaglutide, the active ingredient in medications such as Ozempic® and Wegovy®, has transformed the treatment of obesity and type 2 diabetes. In addition to promoting weight loss and improving glycemic control, it has demonstrated cardiovascular benefits in major clinical trials.

However, recent warnings from regulatory agencies have raised a new concern: a possible association between semaglutide use and a rare ophthalmic condition known as non-arteritic anterior ischemic optic neuropathy (NAION), which can cause sudden and, in some cases, permanent vision loss.

But how significant is this risk? Do all GLP-1 receptor agonists carry the same potential risk? And what does the scientific evidence actually show?

What Does Brazil's Regulatory Agency (Anvisa) Say About Semaglutide?

In 2025, the Brazilian Health Regulatory Agency (Anvisa) issued a warning regarding a possible association between semaglutide and NAION.

The condition was recognized as a very rare adverse event, meaning that its estimated frequency is below 1 case per 10,000 treated individuals, according to the regulatory frequency classification.

Despite its low frequency, the potential severity of this complication justifies regulatory warnings and guidance for healthcare professionals.

This does not mean that everyone taking semaglutide has a high risk of vision loss, nor does it mean that treatment should be routinely discontinued as a precaution.

The purpose of pharmacovigilance is to identify adverse events, promote early recognition, and support safer therapeutic decisions.

What Does the FDA Say?

The U.S. Food and Drug Administration (FDA) has also evaluated the potential risk of NAION associated with glucagon-like peptide-1 receptor agonists (GLP-1 RAs).

Its assessment considers various sources of evidence, including randomized clinical trials, observational studies, and adverse event reports.

One of the main challenges is that NAION is a rare condition, making it difficult to determine its exact frequency and identify differences in risk among individual medications.

Furthermore, patients receiving these treatments frequently have diabetes, obesity, and other vascular risk factors that may independently contribute to optic nerve disorders.

Therefore, it is essential to distinguish three concepts:

Association: when two events occur together more frequently than expected in a given population.

Causation: when sufficient evidence indicates that one factor directly contributes to the production of a particular outcome.

Absolute risk: the actual probability that an individual will experience a specific event.

An increase in relative risk may appear substantial while representing only a small absolute number of cases when the condition itself is very rare.

What Did a Study Involving More Than 370,000 People Find?

A study published by Ramsey and colleagues in JAMA Network Open in 2025 evaluated the association between GLP-1 receptor agonists and ophthalmic complications in individuals with type 2 diabetes.

The study included 370,132 participants, divided into GLP-1 receptor agonist users and a comparison group.

Researchers evaluated several outcomes, including diabetic retinopathy, NAION, and blindness.

1. Ischemic Optic Neuropathy

Researchers identified 96 cases of NAION among GLP-1 receptor agonist users and 79 cases in the comparison group.

The hazard ratio (HR) was 1.26, with a 95% confidence interval of 0.94–1.70.

Although the point estimate was above 1, the difference did not reach statistical significance.

This means that the study did not conclusively demonstrate an increased risk of NAION, but it also cannot rule out a possible increase in risk.

2. Diabetic Retinopathy

Researchers observed a small increase in the incidence of diabetic retinopathy among users of GLP-1 receptor agonists, with an HR of 1.07.

Diabetic retinopathy is a microvascular complication of diabetes that affects the blood vessels of the retina.

One hypothesis explaining the early worsening of retinopathy in certain patients is a rapid and substantial reduction in blood glucose levels, a phenomenon already recognized in individuals with diabetes and preexisting retinopathy.

This mechanism does not necessarily indicate that the medication has a direct toxic effect on the retina.

3. Blindness and Severe Ocular Complications

Interestingly, the study also identified a lower occurrence of blindness among GLP-1 receptor agonist users, with an HR of 0.77.

Among individuals with preexisting diabetic retinopathy, lower rates of certain complications, including vitreous hemorrhage and neovascular glaucoma, were also observed.

These findings suggest that the relationship between GLP-1 receptor agonists and ocular health is more complex than a simple classification of these medications as harmful or protective.

However, because this was an observational study, the findings do not establish a causal protective effect.

Could GLP-1 Medications Also Protect the Eyes?

Although warnings about NAION deserve attention, other studies are investigating potential beneficial effects of GLP-1 receptor agonists on the retina and nervous system.

A scientific review by Luo and colleagues, published in BMC Ophthalmology in 2026, discussed several mechanisms relevant to ocular health.

These include:

Neuroprotection: potential effects on the survival and function of retinal nerve cells.

Reduction of neuroinflammation: modulation of inflammatory processes involved in retinal diseases.

Vascular protection: potential benefits for the function of small retinal blood vessels.

Mitochondrial function: mechanisms related to cellular energy metabolism and reduced oxidative stress.

These findings are scientifically promising, but much of the mechanistic evidence still requires confirmation through additional experimental and clinical studies.

At present, these potential benefits do not justify prescribing GLP-1 receptor agonists specifically to prevent or treat eye diseases.

Why Do Studies Report Different Results?

Interpreting the available evidence requires consideration of important differences between studies.

First, not all studies evaluate the same medication. Some investigate semaglutide specifically, while others analyze different GLP-1 receptor agonists as a single drug class.

Second, study populations may differ in age, diabetes status, obesity, hypertension, and preexisting ophthalmic conditions.

Third, the methods used to identify NAION may vary. Studies based on administrative health records do not always include detailed ophthalmologic confirmation of every diagnosis.

Finally, because NAION is rare, even studies involving thousands of participants may identify relatively few events, limiting the precision of risk estimates.

Therefore, a study that does not identify a statistically significant association cannot definitively exclude a rare risk, just as an isolated observational association does not establish causation.

Scientific evaluation must consider the totality of the available evidence.

Should People Taking Semaglutide Have Regular Eye Examinations?

Ophthalmologic follow-up should be individualized.

People with diabetes should continue to undergo the recommended eye examinations for diabetic retinopathy screening and monitoring, regardless of whether they use semaglutide.

Special attention should be given to patients with preexisting retinopathy, visual symptoms, significant vascular risk factors, or a history of optic nerve disorders.

However, there is currently insufficient evidence to recommend additional ophthalmologic examinations at fixed intervals solely because of semaglutide use in all individuals without diabetes or known eye disease.

The most important consideration is the early recognition of warning symptoms.

Seek immediate medical attention if you experience:

• Sudden vision loss in one or both eyes.

• The sudden appearance of a dark area in your field of vision.

• A significant and unexpected reduction in visual acuity.

In these situations, patients should not wait for a routine appointment.

Is It Necessary to Stop Taking Semaglutide?

The identification of a rare adverse event does not mean that everyone should discontinue treatment.

Semaglutide offers important clinical benefits, particularly in the management of obesity and type 2 diabetes, and in reducing cardiovascular events in certain patient populations.

Decisions about initiating, continuing, or modifying treatment should consider the clinical indication, expected benefits, individual risk factors, and ophthalmologic history.

If NAION is suspected or sudden vision loss occurs, urgent medical evaluation is necessary, including reassessment of the medication.

Decisions about discontinuing or continuing treatment should be made with medical guidance, rather than solely on the basis of news reports or social media posts.

Conclusion: Scientific Information for Safer Decisions

The possible association between semaglutide and non-arteritic anterior ischemic optic neuropathy represents an important medication safety concern.

Regulatory warnings reinforce the importance of clinical vigilance for a rare but potentially serious adverse event.

At the same time, scientific studies have reported heterogeneous findings. Some investigations suggest an increased risk of NAION, while others have not identified a statistically significant association. Research is also exploring potential benefits of GLP-1 receptor agonists for retinal health.

These findings should not be interpreted as a simple contradiction, but rather as part of the ongoing scientific process of evaluating medication safety.

The central message is that the established benefits of semaglutide must be balanced against its potential risks, taking each patient's individual characteristics into account.

In evidence-based medicine, acknowledging risks does not mean creating unnecessary alarm. It means providing reliable information so that patients and healthcare professionals can make safer, more informed, and individualized decisions.

Dr. Andrea Pereira — Physician Specialist in Clinical Nutrition (Nutrology)

Science Check ✓ — The Evidence Behind the Headlines.