FDA Vision Loss Warning for GLP-1 Drugs (Ozempic and Mounjaro): What Is the Real Story?

Vision Loss Warning for Ozempic, Wegovy and Mounjaro Users: Not Panic, Not Trivial

On 9 November 2026 the US Food and Drug Administration (FDA) asked that the labels of all GLP-1 drugs carry a "possible risk" warning about NAION, a disease that affects the optic nerve and can cause sudden vision loss. The news spread fast. One group said "I already knew, I lived it"; another reacted that "the risk is very low and it is being exaggerated." I think both sides are partly right. In this article I explain exactly what the FDA asked for, what data the decision rests on, how large the risk is in absolute terms, why a firm cause-and-effect link cannot be established, and what people taking these drugs should do. I covered the general properties of GLP-1 drugs in my semaglutide (Ozempic) and tirzepatide (Mounjaro) articles (in Turkish).

Why does this matter?

Tens of millions of people take GLP-1 drugs worldwide today. Even a very rare side effect corresponds to real numbers among so many users. On the other hand, these drugs have proven benefits in type 2 diabetes, obesity, and heart-vessel and kidney diseases. Stopping the drug out of unnecessary fear can raise the risk of preventable heart attack and stroke (cardiovascular disease, obesity; both in Turkish).

So the topic must be judged by staying away from both extremes. "Drug that blinds" headlines are as wrong as saying "it's very rare, so it doesn't matter" is incomplete. The right approach is to understand the risk in numbers, know the warning signs and decide according to one's own situation. I described the misleading presentations I often see in health news in my article how the public is misled by seemingly solid research (in Turkish).

What is NAION?

NAION (non-arteritic anterior ischemic optic neuropathy) is a disease caused by a sudden drop in blood flow to the point where the optic nerve begins inside the eye. It usually causes sudden, painless vision loss in one eye. The vision loss is often permanent, and there is no proven effective treatment.

NAION occurs at roughly 2-10 per 100,000 people per year in people over 50. A congenitally narrow, crowded start of the optic nerve ("disc at risk"), high blood pressure, diabetes, sleep apnea, smoking, anemia, kidney disease and an excessive drop in blood pressure at night are known risk factors. Notably, most of these risk factors are already common in people taking GLP-1 drugs (diabetes and insulin resistance, kidney failure; both in Turkish). This is the main problem that makes the relationship between drug and disease hard to assess.

About 40% of patients may show partial recovery of vision. The chance that the other eye will be affected within a few years is about 15%. For this reason, controlling risk factors matters even more in people who have had NAION once.

What exactly did the FDA ask for?

In a drug safety communication published on 9 November 2026, the FDA asked the manufacturers of all GLP-1 drugs sold in the US to add information about a possible increased risk of NAION to the "Warnings and Precautions" section of the label. The decision covers the whole class, regardless of whether the drug is used for diabetes or weight management:

I find three points important in the FDA's statement. First, the risk is described as "possible"; it is not said that the drug causes NAION. Second, it states that NAION reports exist with all GLP-1 drugs on the market. Third, doctors are advised to consider stopping the drug in a patient who develops NAION unless its benefits clearly outweigh the risk (Wegovy, Saxenda, Trulicity).

The evidence behind the decision

The first signal: a risk that looks large in selected patients

In a study published in JAMA Ophthalmology in July 2024, patients attending the neuro-ophthalmology department of Massachusetts Eye and Ear were examined. Over three years NAION occurred in 8.9% of people with type 2 diabetes taking semaglutide and in 1.8% of those taking other diabetes drugs (HR 4.28). In overweight or obese people the rates were 6.7% versus 0.8% (HR 7.64). These percentages look very high because the study included people who had already been referred to a specialist for an eye problem. Describing the risk in the general population with these rates would be wrong. But this study was an important signal that started the investigation of the problem.

National registry studies: about a twofold risk

In a national study in Denmark that examined 424,152 people with type 2 diabetes, the risk of NAION in semaglutide users was about 2.2-fold after other factors were accounted for (HR 2.19; 95% CI 1.54-3.12). In the study that examined Danish and Norwegian data together, the relative risk was calculated as 2.8-fold, and the additional risk as about 1.4-2.5 cases per 10,000 person-years. Based on these data, the European Medicines Agency stated that the risk in people with type 2 diabetes is about twofold, corresponding to about 1 additional case per 10,000 person-years of treatment.

The FDA's own analyses

The FDA pooled 126 randomized clinical trials of GLP-1 drugs: 134,253 patients and a total of 288,879 person-years of follow-up. In this huge dataset there were only 15 possible NAION cases: 10 in those taking a GLP-1 drug and 5 in those taking placebo. The rate was 6.4 versus 3.8 per 100,000 person-years. When the number of cases is this small, even a single case can change the result markedly; therefore the estimate is uncertain.

In Sentinel, the FDA's real-world data system, people with type 2 diabetes who newly started treatment between 2019 and 2024 were compared. The risk with GLP-1 drugs was 43% higher than with DPP-4 inhibitors, but there was no significant difference compared with SGLT-2 inhibitors. The FDA also noted that no mechanism by which these drugs could increase NAION risk was found in animal studies.

How large is the absolute risk?

The difference between relative risk ("twofold") and absolute risk ("in how many people") is at the center of this debate. Twice a very rare event is still a very rare event. Imagine 10,000 people taking a GLP-1 drug for a year:

• According to clinical trials: about 0.3 additional NAION cases; that is, about 38,000 person-years of treatment are needed to see one additional case.
• According to registry studies: about 1-2.5 additional cases.
• For comparison: in people with type 2 diabetes, about 3 NAION cases per 10,000 people per year are expected anyway, independent of the drug.

However, it must be remembered that tens of millions of people take these drugs. Even if the individual risk is very low, it can correspond to hundreds of additional cases per year across society. This is why knowing the warning signs and seeking help early matter (diabetes in the world and in Türkiye, in Turkish).

Why can a firm cause-and-effect link not be established?

• Shared risk factors: Diabetes, high blood pressure, sleep apnea, smoking, anemia and kidney disease are risk factors for NAION and are also common in people taking GLP-1 drugs. However much observational studies account for them, unmeasured differences may remain (smoking and vascular health, in Turkish).
• Results that change with the comparator drug: The risk is higher compared with DPP-4 inhibitors and not significant compared with SGLT-2 inhibitors. This leaves open the question of whether the finding comes from the drug or from differences between patient groups.
• Very few events: In clinical trials involving more than 134,000 patients there are only 15 possible cases in total.
• Unclear mechanism: No mechanism was found in animal studies. Possibilities such as a rapid fall in blood sugar affecting the eye's blood vessels, changes in night-time blood pressure or fluid loss have been put forward; none is proven.

Nevertheless, the FDA and the European Medicines Agency found it sufficient for adding a warning that data from different countries and with different methods point in the same direction. I also see this as the right approach: informing patients and doctors while waiting for definitive evidence is the way to minimize possible harm. I described the difference between a clinical trial and an observational study in my article what is a clinical trial? (in Turkish).

As a separate matter, in people with diabetic retinopathy, a rapid fall in blood sugar can cause a temporary worsening of retinopathy. In the SUSTAIN-6 trial, retinopathy complications were more frequent with semaglutide, 3.0% versus 1.8%. This is different from NAION but carries the same message: people with diabetes should not neglect regular eye examinations (retina and blood sugar).

Those who say "I already lived it" and those who say "the rate is very low"

Two different reactions stood out on social media after the warning. Both deserve to be approached with respect.

For those who say "I lived it": What someone who has lost vision has gone through is real and serious. There are NAION reports with these drugs, and adding the warning shows that these reports are being taken seriously. However, in a single person it is often impossible to tell with certainty whether NAION came from the drug or from causes such as diabetes, blood pressure, sleep apnea or a congenitally narrow start of the optic nerve. If you have had such an experience, reporting it to your doctor and to TÜFAM helps strengthen the data.

For those who say "the rate is very low": That is true. The absolute risk is small next to the cardiovascular and kidney benefits the drug provides. But low risk does not mean zero risk; NAION can cause permanent vision loss. That is why knowing the symptoms and acting quickly matters. It should not be forgotten that fear itself can also affect adherence to the drug and the perception of side effects (the nocebo effect, in Turkish).

What should you do if you take a GLP-1 drug?

• Do not stop the drug on your own. Most people gain proven benefits from these drugs; the decision to stop should be made together with your doctor (obesity and cardiovascular disease).
• Know the warning signs: Sudden, painless loss of vision in one eye (especially on waking in the morning), a curtain or blind spot in the visual field, tunnel vision, faded colors, blurred or hazy central vision. In this case see an eye doctor the same day.
• If you have had NAION before, the risk of recurrence is higher; talk to your doctor about this before starting or continuing the drug.
• Bring risk factors under control: Measure your blood pressure regularly, get evaluated if you have signs of sleep apnea (snoring, daytime sleepiness), and quit smoking (how can I quit smoking?, loss of life caused by smoking; both in Turkish).
• If you have diabetes, have an eye examination at least once a year.
• Switching drugs may not be the solution: the FDA warning covers the whole GLP-1 class.

The situation in Türkiye

With the European Medicines Agency's decision of June 2025, NAION was added to the information of semaglutide-containing products in Europe as a "very rare" side effect. I could not verify, at the time of writing, whether the Turkish Medicines and Medical Devices Agency (TİTCK) has issued a separate announcement similar to the FDA's class warning. I recommend that you read the current package leaflet of the product you use and report possible side effects to the Turkish Pharmacovigilance Center (TÜFAM). I covered the discussions about other possible side effects of these drugs in my articles GLP-1 drugs and depression and GLP-1 drugs and sexual desire (in Turkish).

Questions you can ask your doctor

• What is the benefit of this drug for me; given the vision risk, is that benefit large enough?
• Do I have additional risk factors for NAION (sleep apnea, blood pressure, anemia)?
• Should I have an eye examination before starting treatment?
• If my vision changes, whom should I contact, and how quickly?
• If I have had NAION before, can I use this drug?

Frequently Asked Questions

Do GLP-1 drugs cause vision loss?

There is a possible association between GLP-1 drugs and NAION, an optic nerve disease that can cause sudden vision loss. For this reason the FDA asked in November 2026 that a warning be added to the label of the whole class. However, the risk is very low and a definite cause-and-effect relationship has not been proven.

How large is the NAION risk?

In 126 clinical trials, NAION occurred at 6.4 per 100,000 person-years with GLP-1 drugs and 3.8 in comparison groups. According to registry studies, the additional risk is about 1-2.5 cases per 10,000 person-years. The European Medicines Agency classified this as "very rare" (up to 1 in 10,000 people).

I take Ozempic or Wegovy; should I stop the drug?

Do not stop on your own. The benefits of these drugs for the heart, kidneys and metabolism clearly outweigh the vision risk in most people. If you have had NAION before or your vision changes, make the decision to continue together with your doctor.

Which symptoms mean I should see a doctor?

If you have sudden, painless loss of vision in one eye, vision loss noticed especially on waking in the morning, a curtain or blind spot in the visual field, tunnel vision, faded colors or blurred central vision, see an eye doctor the same day.

Glossary

NAION

Non-arteritic anterior ischemic optic neuropathy; sudden vision loss caused by reduced blood flow to the start of the optic nerve.

Optic nerve

The nerve that carries visual information from the eye to the brain.

GLP-1 drugs

Drugs used in diabetes and obesity that mimic the effect of the gut hormone GLP-1.

Warnings and Precautions

The section of a drug label that lists important safety risks and the precautions to take.

Relative risk

How many times higher the risk in one group is compared with another (for example, twofold).

Absolute risk

How many times an event is actually seen in a given number of people (for example, 1 in 10,000).

Person-year

The number of people multiplied by follow-up time; following 10,000 people for one year is 10,000 person-years.

Observational study

A study that compares people who use a drug in real life with those who do not, without assigning the drug at random.

Sentinel

The data system with which the FDA monitors drug safety using insurance and health records.

TÜFAM

Turkish Pharmacovigilance Center; the official center where drug side effects are reported.