Can weight-loss injections affect your eyesight? NAION, a rare condition that damages the optic nerve, has been recognised by the European Medicines Agency as a very rare side effect of semaglutide. The evidence for tirzepatide is less established, and its additional risk has not been reliably quantified.

For patients with normal vision, these findings do not usually mean treatment must be stopped. The decision should take account of the benefits of treatment, medical history and eye-related risk factors. Sudden visual changes, however, require immediate assessment.

This guide explains what the research shows, how to interpret the reported risks and what patients in Singapore should discuss with their prescribing doctor.

If you develop sudden loss of vision, a new missing area in your vision or rapidly worsening eyesight, attend A&E or an emergency eye service immediately, even if there is no pain.

What Is NAION?

Non-arteritic anterior ischaemic optic neuropathy (NAION) occurs when blood flow to the front of the optic nerve is reduced. This nerve transmits visual information from the eye to the brain. Disruption to its blood supply can damage nerve fibres and cause lasting visual impairment.

“Non-arteritic” means that the condition is not caused by inflammation of the arteries. NAION can occur without weight-loss medication use, particularly in people with susceptible optic nerve anatomy or underlying vascular risk factors.

What Are the Symptoms of NAION?

NAION typically causes sudden, painless visual impairment in one eye. Some people notice the change on waking. Symptoms can include:

• Blurred, dim or cloudy vision.
• A fixed dark or grey area in the visual field.
• Loss of the upper or lower portion of vision.
• Colours appearing less vivid in the affected eye.

NAION does not always cause complete blindness. Some patients retain central vision while losing part of their visual field. Vision can improve in some cases, but permanent impairment is possible and no treatment has been reliably shown to restore lost vision.

Source: North American Neuro-Ophthalmology Society patient information::
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Why Are Weight-Loss Injections Being Linked to Vision Loss?

The concern gained attention after a 2024 study at a specialist neuro-ophthalmology centre found a higher observed rate of NAION among patients prescribed semaglutide than among comparison patients receiving other treatments for diabetes or weight management.

The study identified an important safety signal, but its specialist patient population was not representative of everyone taking semaglutide. Its high reported percentages should not be used to predict the risk for a typical weight-management patient.

Original study: Risk of Nonarteritic Anterior Ischemic Optic Neuropathy in Patients Prescribed Semaglutide:
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Does an Association Prove That the Medication Caused NAION?

An association shows that events occur together more often; it does not establish causation on its own. Diabetes, hypertension and sleep apnoea are relevant to NAION and may already be present in people receiving these medicines.

Researchers adjust for these differences, but medical-record studies cannot capture every factor, including detailed optic nerve anatomy. Later studies have produced differing results. Nevertheless, the accumulated evidence has led regulators to update safety information, particularly for semaglutide.

News reports and lawsuits should therefore be interpreted alongside published research and regulatory assessments. Legal claims alone cannot establish either the cause of an individual case or the frequency of a medication-related risk.

Semaglutide and NAION: What Does the Evidence Show?

In June 2025, the European Medicines Agency concluded that NAION is a very rare side effect of semaglutide, following review of clinical trials, observational studies and post-marketing reports. This recognition does not mean that semaglutide is unsuitable for all patients.

How Large Is the Risk With Semaglutide?

The EMA review described an approximately twofold increase in NAION risk in several large studies of adults with type 2 diabetes. It estimated approximately one additional case per 10,000 person-years of treatment: roughly one extra case among 10,000 people treated for one year.

This is an estimate of additional annual risk, not the total number of cases expected or a personal prediction. The EMA also uses the product-information category “very rare”. The frequency category and estimated annual excess risk should not be treated as interchangeable statistics.

European Medicines Agency safety review:
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Why Do Different Studies Report Different Risks?

Risk estimates depend on the patients studied, how NAION is identified, the comparison medication and follow-up duration. For example, a 2026 study of US veterans with type 2 diabetes found a higher NAION rate among semaglutide initiators than among those starting SGLT2 inhibitors. The population was predominantly male and had substantial cardiometabolic risk, limiting direct application to other patients.

These differences are a reason to interpret the evidence carefully, rather than select the lowest or highest published number as the risk for everyone.

Original study: New-Onset Nonarteritic Anterior Ischemic Optic Neuropathy and Initiators of Semaglutide in US Veterans With Type 2 Diabetes:
https://jamanetwork.com/journals/jamaophthalmology/fullarticle/2844873

Does the Same Risk Apply to People Taking Semaglutide for Weight Loss?

Much of the evidence comes from people with type 2 diabetes, whose underlying NAION risk is already higher. These findings cannot automatically be applied to every patient receiving semaglutide for weight management.

A 2026 systematic review that analysed diabetes and weight-loss use separately found no statistically significant increase in the weight-loss observational studies. However, the estimates were imprecise, so an increased risk could not be excluded. The finding offers some reassurance but does not establish that people without diabetes face no risk.

Systematic review: Rate and Risk of Nonarteritic Anterior Ischemic Optic Neuropathy with Semaglutide Use for Diabetes and Weight Loss:
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For background on how semaglutide is used in weight management, read our semaglutide 2.4 mg treatment guide:
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Singapore Reporting Update: September 2026

According to information provided to our clinic by Novo Nordisk Singapore, as of 24 September 2026, no cases of NAION associated with semaglutide use in Singapore had been reported to the company.

This reflects reports known to the company at that time, rather than a comprehensive national case count. It does not establish that no cases have occurred or that the risk is absent. International safety findings remain relevant when assessing treatment suitability.

Tirzepatide and NAION: Is the Risk Different?

Tirzepatide acts on both GIP and GLP-1 receptors, whereas semaglutide acts on GLP-1 receptors. The medicines differ, but this alone does not establish a difference in eye safety.

What Have Studies Found About Tirzepatide?

A 2025 JAMA Network Open study compared patients with type 2 diabetes prescribed semaglutide or tirzepatide with matched patients receiving other diabetes medicines. Over two years, NAION was recorded in 35 of 79,699 patients in the combined treatment group and 19 of 79,699 comparators: approximately 0.04% versus 0.02%.

The main analysis pooled the two medicines. It therefore cannot establish a tirzepatide-specific risk. A separate direct comparison had only two NAION cases among semaglutide users and one among tirzepatide users, too few to conclude that either medicine is safer.

Original study: Semaglutide or Tirzepatide and Optic Nerve and Visual Pathway Disorders in Type 2 Diabetes:
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What Have Regulators Said About Tirzepatide?

Australia’s Therapeutic Goods Administration published updated safety information in July 2026. Its advisory committee had considered the evidence supportive of a possible signal for semaglutide, but not established for tirzepatide or dulaglutide. Tirzepatide information nevertheless now acknowledges NAION reports involving medicines with GLP-1 receptor activity.

The practical message is to recognise visual symptoms while acknowledging the uncertainty. Less evidence of harm is not proof of no risk, and switching medication solely to avoid NAION is not supported by a reliable comparison.

Australian Therapeutic Goods Administration safety update:
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Learn more about tirzepatide and individual treatment assessment:
Read more...

Who May Be at Higher Risk of NAION?

NAION susceptibility reflects eye anatomy and general health. Associated factors include type 2 diabetes, hypertension, high cholesterol, smoking, obstructive sleep apnoea and increasing age. Having one of these factors does not mean that NAION will occur or automatically rule out weight-management treatment.

Why Does Optic Nerve Anatomy Matter?

A naturally crowded optic disc, sometimes called a “disc at risk”, may be more vulnerable to disruption of its blood supply. An eye professional can assess this anatomy; symptoms alone cannot identify it.

Previous NAION is particularly relevant because the other eye can be affected later, independently of medication use. Patients with this history should discuss treatment with their prescribing doctor and ophthalmologist.

Should You Have an Eye Examination Before Treatment?

An examination may be useful for patients with previous NAION, known optic nerve abnormalities or unexplained visual symptoms. Whether to arrange one should be considered individually; it is not a guarantee against future NAION.

Patients with diabetes should continue their recommended diabetic eye screening. Managing blood pressure, cholesterol and sleep apnoea and stopping smoking supports overall health, but has not been proven to eliminate medication-associated NAION risk. Do not change blood-pressure medication independently.

Background on risk factors and clinical assessment:
https://www.gov.uk/drug-safety-update/semaglutide-wegovy-ozempic-and-rybelsus-risk-of-non-arteritic-anterior-ischemic-optic-neuropathy-naion

What Should You Do if Your Vision Changes During Treatment?

Not every visual change is NAION, but sudden or rapidly worsening symptoms need urgent assessment to identify the cause. Other eye emergencies can produce similar symptoms.

When Should You Attend A&E or an Emergency Eye Service?

Seek immediate assessment for sudden reduced vision, a new dark or missing area, persistent sudden blurring, or a shadow or curtain across your vision. Do not wait for pain to develop or for vision to be completely lost.

In Singapore, attend A&E or an emergency eye service rather than wait for a routine clinic appointment or WhatsApp reply. Avoid driving yourself if your vision is affected.

Tell the assessing clinician when symptoms began, which eye is affected, and whether they are progressing. Provide your medication name, dose, treatment start date, last injection date and any recent dose changes, together with your eye and medical history.

What About Your Next Injection?

Urgent eye assessment takes priority. Obtain advice from the assessing clinician or prescribing doctor before your next dose.

If NAION is confirmed during semaglutide treatment, regulatory guidance recommends discontinuing semaglutide. For tirzepatide, the prescribing doctor and ophthalmologist should decide the next steps according to the diagnosis and individual circumstances. Patients using medication for diabetes may need an alternative glucose-management plan if treatment is interrupted.

UK Medicines and Healthcare products Regulatory Agency guidance:
https://www.gov.uk/drug-safety-update/semaglutide-wegovy-ozempic-and-rybelsus-risk-of-non-arteritic-anterior-ischemic-optic-neuropathy-naion

Should You Continue Weight-Loss Treatment if Your Vision Is Normal?

News reports alone do not generally require treatment to be stopped in patients without visual symptoms. Discuss concerns with your prescribing doctor, particularly if the medicine also helps manage diabetes.

The benefits and risks differ between patients. Someone with obesity and substantial weight-related health problems may have more to gain from treatment than someone seeking a small amount of weight loss. Relevant considerations include progress, side effects, diabetes control and any previous optic nerve disease.

What Does a Favourable Benefit–Risk Profile Mean?

A medicine can retain a favourable benefit–risk profile even when a rare, serious adverse effect is recognised. The phrase means its expected benefits outweigh its potential harms in an appropriately selected population; it does not mean that every patient should receive it or that adverse effects can be dismissed.

Novo Nordisk Singapore’s holding statement supplied to our clinic states that the company continues to consider semaglutide’s overall benefit–risk profile favourable. This is the manufacturer’s position and should be read alongside independent regulatory assessments and the patient’s individual circumstances.

A review can help determine whether to continue the current plan, adjust it or consider another approach. Bring your medication details, progress and any relevant eye specialist reports.

Discuss Your Weight-Management Treatment With Dr Edwin Lim

If you have concerns about NAION or other medication risks, Dr Edwin Lim can review your treatment response, side effects and relevant medical history at Edwin Lim Medical Aesthetic Clinic. Previous NAION and known optic nerve conditions should be highlighted. An ophthalmologist’s assessment may help guide the decision where appropriate.

Learn more about doctor-supervised medical weight management:
https://weightlossclinic.sg/medical-weight-loss-singapore/

To arrange a consultation at our Changi City Point or Orchard clinic:
https://weightlossclinic.sg/contact-us/

Phone: +65 6904 2218
WhatsApp: +65 9637 2218
Email: hello@edwinlimclinic.sg

Sudden loss of vision or rapidly worsening eyesight requires emergency assessment rather than a routine consultation.