Can Ozempic or Wegovy cause eye problems?
Yes, rarely. In June 2025 the safety committee of the European Medicines Agency (EMA) finished its review of semaglutide and concluded that NAION is a very rare side effect, meaning it may affect up to 1 in 10,000 people taking semaglutide. The review covered Ozempic, Wegovy and Rybelsus, and weighed laboratory data, clinical trials, post-marketing reports and the published literature.
NAION stands for non-arteritic anterior ischaemic optic neuropathy. It is a loss of blood flow to the front of the optic nerve that can cause sudden loss of vision. The EMA advises that treatment with semaglutide should be stopped if NAION is confirmed. This page covers the eyes only; the wider list of effects is in the clinic's guide to weight-loss injection side effects.
What do the studies behind the NAION signal show?
Several large observational studies suggested an approximately two-fold higher risk of NAION in adults with type 2 diabetes taking semaglutide, according to the EMA. That corresponds to about one additional case per 10,000 person-years of treatment. A Danish and Norwegian register study of about 61,000 people with type 2 diabetes found 32 NAION events, a pooled hazard ratio of 2.81 against people starting a different diabetes medicine (SGLT-2 inhibitors), and an extra 1.41 cases per 10,000 person-years. Its authors conclude that the absolute risk remains low.
An earlier study from a Boston neuro-ophthalmology registry reported much larger ratios, 4.28 in people with type 2 diabetes and 7.64 in people with overweight or obesity. That cohort was made up of people already referred to eye specialists, which makes its percentages impossible to apply to the general public, and its authors say causality remains to be shown. Read together, the studies agree on the direction and disagree on the size, which is why the regulator's wording is "very rare" and not a single number for any one person.
What do diabetic retinopathy and early worsening have to do with it?
They are a separate eye risk from NAION, and they concern people who already have diabetes. In SUSTAIN-6, a two-year trial of 3,297 adults with type 2 diabetes, retinopathy complications (bleeding into the eye, blindness, or a need for an injection into the eye or laser treatment) were more frequent on semaglutide than on placebo, with a hazard ratio of 1.76.
A later analysis by the same programme attributed most of that effect to how far and how fast HbA1c fell in the first 16 weeks in people who already had retinopathy, poor control at baseline and treatment with insulin. Early worsening of retinopathy after a rapid improvement in blood sugar is a known phenomenon, and the authors suggested that the guidance given with insulin may be appropriate for semaglutide too. These are trial findings in people with diabetes. They do not show that the same happens in someone with normal blood sugar who is losing weight.
Does Mounjaro (tirzepatide) affect the eyes too?
The evidence is less settled for tirzepatide (Mounjaro) than for semaglutide. The EMA conclusion is about semaglutide only. A US records study of 79,699 matched pairs with type 2 diabetes pooled semaglutide and tirzepatide together and found NAION in 0.04% of people on either medicine against 0.02% on other diabetes medicines over two years, a hazard ratio of 1.76 with a wide range of uncertainty (1.01 to 3.07). Because the two were combined, that study cannot say what tirzepatide does by itself.
In practice, the sensible reading is caution rather than alarm: the same warning about sudden vision change applies to every medicine in this class, and the data will keep being updated. The clinic's page on how liraglutide, semaglutide and tirzepatide compare sets the three side by side.
Why can vision blur in the first weeks?
Blood sugar that changes quickly can blur vision, and that is a common reason, separate from NAION. In a small case series of five people with newly diagnosed diabetes and very high sugar, intensive glucose lowering was followed by temporary farsightedness. It peaked on average at about 12 days with insulin and had recovered by about 2 months. The study is small, and it describes people with diabetes, not everyone on a weight-loss injection.
The practical point is that the first weeks of a new dose are also when blur is most likely to be noticed. A gradual, both-eyes change in the days after a blood sugar shift is a reason to see an optometrist or eye doctor. A sudden change, especially in one eye, is a different matter, covered below.
Who should have an eye check before starting?
Anyone with diabetes, and above all anyone with known diabetic retinopathy, should have the eyes examined and the result shared with the prescribing doctor before a GLP-1 medicine starts. The reasoning comes from SUSTAIN-6: the extra retinopathy complications were concentrated in people who already had retinopathy and whose sugar fell quickly. How to proceed, and how closely the eyes are watched, is a decision for the treating doctor.
It also helps to mention any earlier episode of sudden vision loss or optic nerve problem. A good history is part of the checks described in what a doctor checks before prescribing a GLP-1 medicine.
When is sudden vision loss an emergency?
Always, when it comes on suddenly. If you lose vision in one eye, or your eyesight worsens rapidly, go to an emergency department the same day. Do not wait for a clinic appointment, do not wait to see whether it improves overnight, and ask the emergency doctor about the next injection. The EMA's own advice is to contact a doctor without delay, and to stop semaglutide if NAION is confirmed.
The same symptoms can come from other conditions that also need urgent treatment, such as a blocked retinal artery or a detached retina. Only an examination can tell them apart, which is the reason for the same-day rule.
What should I do if my vision changes while on a weight-loss injection?
Sort the change by how it arrived. A sudden loss of vision, a dark patch that appears over hours, or eyesight that worsens quickly is an emergency, as above. A slower, mild blur in both eyes during the first weeks, especially if blood sugar is changing, deserves a prompt eye examination and a message to the prescribing doctor, so the two can be considered together.
Bring the name and dose of the medicine, the date of the last injection, and any history of diabetes, high blood pressure or earlier eye problems. Do not stop a prescribed diabetes medicine on your own because of a search result, and do not restart one after an eye event without the treating doctor and the eye doctor agreeing.
What happens at a medical weight management visit?
The Retreat Clinic in Setia Alam offers medical weight management with GLP-1 and tirzepatide medicines. Dr Ong tailors the dose and holds weekly reviews early on, which gives a set point to report any change in vision, along with nausea, dehydration or other effects. The clinic's page on medical weight management in Setia Alam describes the programme, and a medicine is only prescribed after an assessment.
Facial changes on these medicines have their own article: what changes and what helps with Ozempic face and Mounjaro face is a separate read. You can message the clinic on WhatsApp with questions; for sudden vision loss do not message first, go to an emergency department.
The honest complication
The numbers here have limits. The EMA frequency is a regulator's band, not a prediction for one person, and observational studies can show an association without proving a cause. Two of the sources above were funded by or include employees of the manufacturer, and the registry study came from a referral clinic. What is solid is the behaviour that follows: tell your doctor about diabetic eye disease before starting, report vision changes early, and treat sudden vision loss as an emergency.
