Eye changes in the GLP-1 labels

What the product documents say

Two different eye topics appear in GLP-1 product information. Every US label we reviewed for semaglutide, tirzepatide and orforglipron has a warning on diabetic retinopathy complications ^{[1][2][3][4][5][6]}. NAION appears only outside the US so far: in the EU product information for semaglutide and in the Canadian tirzepatide monograph ^[7][9]. Searching the nine US labels for the condition and for the optic nerve found no mention.

• The retinopathy figures all come from people with type 2 diabetes. The US Wegovy® and Zepbound® warnings are written for that group ^[2][5].
• The Ozempic® label adds that the long-term effect of semaglutide’s glucose control on these complications has not been studied ^[1].

The retinopathy finding, in detail

SUSTAIN 6 enrolled 3,297 adults with type 2 diabetes and heart or kidney disease, or other heart risk factors, and followed them for at least two years ^[1]. Retinopathy complications were counted as a combined, independently reviewed outcome. The European product information lists what it included: laser treatment of the retina, injections into the eye, bleeding inside the eye and diabetes-related blindness ^[7].

The European text is more specific about who was affected. It says the excess appeared in insulin-treated patients who already had retinopathy, that the difference showed up early and lasted through the trial, and that the risk was only formally measured in this one trial ^[7]. In shorter trials, retinopathy events were similar with semaglutide and with comparators ^[7]. It also advises against the highest Ozempic® dose in people with unstable or poorly controlled retinopathy, because there is no experience with it ^[7].

A later post hoc analysis of SUSTAIN 6 data found that most of the difference could be explained by how far and how quickly HbA1c fell in the first 16 weeks, in people with existing retinopathy, poor control and insulin treatment ^[10]. An analysis like this can suggest an explanation but not prove one. The tirzepatide labels describe the same early-worsening idea without SUSTAIN data ^[4][5].

NAION: what the EMA concluded and what US labels leave out

NAION, non-arteritic anterior ischemic optic neuropathy, is damage to the front of the optic nerve from reduced blood supply. The European package leaflet describes it as possible loss of vision in one eye, without pain ^[7]. In June 2025 the EMA’s safety committee reviewed trials, post-marketing reports and published studies and classed NAION as a very rare side effect of semaglutide medicines, a category covering up to 1 person in 10,000 ^[8].

The committee based its size estimate on large epidemiological studies in adults with type 2 diabetes: roughly a doubling of risk, about one extra case per 10,000 person-years of treatment. It added that clinical trial data also pointed to a slightly higher risk than placebo ^[8]. The EU product information now says there is no known time window after starting when NAION may appear, and that semaglutide should be stopped if NAION is confirmed ^[7].

For tirzepatide, the Canadian Zepbound® monograph added a NAION warning in June 2026. It says events have been reported with GLP-1 medicines as a group, asks for urgent referral to an eye specialist after any sudden loss of vision, including partial loss, and lists NAION among post-marketing reports, where frequency and cause cannot be reliably established ^[9]. The US labels we checked, revised up to August 2026, do not mention NAION ^{[1][2][3][4][5][6]}.

What studies on NAION report

• Hathaway 2024, retrospective cohort at one US neuro-ophthalmology service: among patients seen there, NAION was more common in those prescribed semaglutide, both with type 2 diabetes and with overweight or obesity. The authors say causality needs further study ^[11]. Patients referred to an eye specialist are not typical of everyone on the medicine.
• Simonsen 2025, national registries in Denmark and Norway: in about 61,000 people with type 2 diabetes starting semaglutide, NAION was more frequent than in people starting an SGLT-2 inhibitor, with 32 events in total. The extra risk was about 1.4 cases per 10,000 person-years, and the authors stress that the absolute risk stays low ^[12].
• Vilsbøll 2026, pooled placebo-controlled trials of liraglutide and semaglutide: across about 97,000 participants, three confirmed cases occurred on the medicines and five on placebo. Every confirmed case had other risk factors. Several authors are employees of the manufacturer, and with eight confirmed cases in all, the comparison is imprecise ^[13].
• Observational studies can be skewed by differences between people who get one medicine or another, and they cannot show cause. The EMA review came before that pooled analysis was published, and described the trial data it had seen as pointing to a slightly higher risk ^[8][13].

Why it may happen

• Supported by the labels: a fast drop in blood sugar has been linked to temporary worsening of existing diabetic retinopathy ^[1][4][5]. The European text adds that other mechanisms cannot be excluded ^[7].
• Proposed but not measured: the SUSTAIN 6 analysis points to the size and speed of the early HbA1c fall, mostly in people on insulin with existing retinopathy ^[10]. No study has shown a mechanism for NAION, and the regulators do not describe one ^[8][9].
• General: in the trial pool, every confirmed NAION case had risk factors such as age over 50, obesity, smoking, high blood fats or high blood pressure ^[13]. High blood glucose over time damages the small vessels of the retina, which is why diabetes itself is the main cause of retinopathy ^[14].

What else could it be

Not every eye change on a GLP-1 medicine is retinopathy or NAION. NIDDK notes that people sometimes have blurry vision for days or weeks when they change their diabetes plan or medicines, because glucose shifts fluid in the parts of the eye that focus; this kind of blur goes away as glucose settles ^[14]. Blurred vision with shakiness, sweating or hunger can be a sign of low blood sugar, which the Ozempic® Medication Guide lists, especially alongside insulin or a sulfonylurea ^[1].

MedlinePlus lists many other causes of vision change: needing reading glasses with age, cataracts, glaucoma, macular degeneration, retinal detachment, migraine, stroke and inflammation of the artery that supplies the optic nerve ^[15]. That last one, temporal arteritis, is what the word non-arteritic in NAION rules out.

What may help

If you have diabetes, regular dilated eye exams are part of usual care. NIDDK advises most people with diabetes to see an eye care professional every year, and more often if they advise it, alongside managing blood glucose, blood pressure and cholesterol and not smoking ^[14]. Telling your eye specialist which GLP-1 medicine you take, and when it started, helps them time the checks.

Before starting, the Medication Guides ask you to mention a history of diabetic retinopathy ^[1][2]. During treatment, the labels ask you to report any change in vision ^[1][4][6]. MedlinePlus advises a full eye exam for vision changes that seem related to a medicine, and not stopping or changing the medicine on your own ^[15].

Ozempic®, Wegovy® and Rybelsus® are registered trademarks of Novo Nordisk A/S. Mounjaro® and Zepbound® are registered trademarks and Foundayo™ is a trademark of Eli Lilly and Company. PepLabo is not affiliated with or endorsed by Novo Nordisk or Eli Lilly and Company.

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