It’s been in the news lately that injectable weight-loss medication can cause blindness. Two different eye concerns come up with semaglutide and tirzepatide. They are unrelated to each other, and they warrant different levels of concern.

Temporary Worsening of Diabetic Retinopathy

This one is well established and appears in the FDA labeling for both Wegovy and Zepbound.^1,2 The drugs cause rapid improvement in insulin resistance and blood sugar control. Better control sounds like a good thing, but it inevitably results in a temporary increase in the frequency of low blood sugars, which are the culprit here.

In response to the stress of low blood sugars, retinal cells are stimulated to release a protein called Vascular Endothelial Growth Factor (VEGF). It’s a cytokine that stimulates rapid growth of new blood vessels in the retina. Such vessels are extra-prone to rupturing and leaking, so existing diabetic eye disease can temporarily accelerate before it stabilizes. This problem is not unique to GLP-1 medications — it is a long-recognized effect of any rapid improvement in glucose control, including insulin.

In the two-year SUSTAIN-6 trial of semaglutide in adults with type 2 diabetes,³ retinopathy complications occurred in 3.0% of treated patients versus 1.8% on placebo. The difference was concentrated almost entirely among people who already had retinopathy when they started (8.2% versus 5.2%). Among those without it, the rates were 0.7% versus 0.4%.

Tirzepatide has not been formally studied in patients with proliferative diabetic retinopathy, but the risks associated with semaglutide are believed to apply to it.

The practical take-away

If you have diabetes and known retinopathy, you should probably have a dilated eye exam before starting either semaglutide (Wegovy) or tirzepatide (Zepbound), and you should be monitored during treatment.

The longer-term retinopathy picture for GLP-1 treatment is more favorable. A 2026 study of more than 173,000 adults with type 2 diabetes and pre-existing retinopathy found that GLP-1 users were less likely to progress to proliferative retinopathy and had fewer retinal vein occlusions.⁸

If you do not have diabetes, this warning does not really apply to you.

NAION: An Unsettled Question

Non-arteritic anterior ischemic optic neuropathy (NAION) is the sudden, usually painless loss of vision in one eye caused by interrupted blood flow to the optic nerve. It typically affects people over 50, and vision loss is often permanent. It is uncommon in the general population.

In 2024, researchers at Massachusetts Eye and Ear reported higher NAION rates among patients taking semaglutide.⁴ Studies since have not agreed:

A 2025 analysis of nearly 483,000 matched pairs found an 85% relative increase compared with a different diabetes medication — but the absolute difference was roughly 0.29 additional cases per 1,000 person-years.⁵
A 2026 meta-analysis pooling eight studies and 14 million people found approximately a two- to threefold increased risk.⁶
A 2026 study of 1.2 million Military Health System patients found lower NAION risk among semaglutide users with diabetes, and no association among those taking it for weight.⁷
The 173,000-patient study noted above found no NAION association.⁸

European and UK regulators reviewed this evidence and classified NAION as a “very rare” side effect of semaglutide — affecting up to 1 in 10,000 people — and required it be added to product information. As of mid-2026, the FDA has not added a NAION warning to US labeling for Ozempic, Wegovy, or Zepbound.

How We Approach It

The overall risk of serious eye complications from these medications remains low, and for most patients the many metabolic benefits outweigh it. Nonetheless, these possibilities should be discussed ahead of time. We ask about your eye history before prescribing injectables. If you have longstanding diabetes or any history of diabetic retinopathy, we will recommend you undergo a dilated exam if there has been none recently. If you are over 50, or have been told you have a “crowded” optic disc, we will discuss the risk-benefit balance of proceeding with therapy in a one-on-one session in the office.

Call us immediately — or see an eye doctor — if you experience sudden vision loss, a dark area or blind spot in your vision, or sudden blurring in one eye. Do not wait. NAION cannot be reversed once established, but sudden vision changes have other causes that are treatable and need prompt evaluation.

References

Wegovy®, Prescribing Information, Novo Nordisk, 2022: accessdata.fda.gov
Zepbound®, Prescribing Information, Eli Lilly, 2026: pi.lilly.com
Marso SP, Bain SC, Consoli A, Eliaschewitz FG, et al. Semaglutide and Cardiovascular Outcomes in Patients with Type 2 Diabetes. N Engl J Med. 2016 Nov 10;375(19):1834-1844. PMID: 27633186.
Hathaway JT, Shah MP, Hathaway DB, et al. Risk of Nonarteritic Anterior Ischemic Optic Neuropathy in Patients Prescribed Semaglutide. JAMA Ophthalmol. 2024 Aug 1;142(8):732-739. PMID: 38958939.
Tesfaye H, et al. GLP-1RA and the risk of non-arteritic anterior ischaemic optic neuropathy in patients with type 2 diabetes: a population-based study. Diabetes Obes Metab. 2025. doi:10.1111/dom.70200
Lampsas S, Agapitou C, Oikonomou E, et al. Semaglutide and risk of Non-Arteritic Anterior Ischemic Optic Neuropathy (NAION) in type 2 diabetes mellitus: a systematic review and meta-analysis. Graefes Arch Clin Exp Ophthalmol. 2026. doi:10.1007/s00417-026-07291-4
Lieberman RA, et al. Semaglutide decreases risk of non-arteritic anterior ischemic optic neuropathy in type 2 diabetic patients. Mil Med. 2026. doi:10.1093/milmed/usaf522
Shah J, Makwana B, Panchal K, et al. Glucagon-like peptide-1 receptor agonists and risk of systemic and ocular vascular complications in patients with type 2 diabetes and diabetic retinopathy. Am J Ophthalmol. April 19, 2026.