How long does naion (sudden vision loss) last?

Onset typically weeks to a few months after starting or dose-escalating. Peak reporting in the 90-day window per FAERS post-marketing signals.

How common is naion (sudden vision loss) on GLP-1?

Adjusted hazard ratio ~4.28 (T2D) and ~7.64 (obesity) vs non-GLP-1 controls in the 2024 Hathaway et al. cohort. Absolute incidence remains rare: ≤0.05% of users over 3 years in the studied population.

Does Ozempic cause hair loss?

Not directly. Hair shedding (telogen effluvium) is reported by some patients ~3 months into rapid weight loss — typical of any rapid-weight-loss state, not unique to GLP-1.

What foods should you avoid on a GLP-1?

Avoid greasy, fried, and ultra-processed foods (worst nausea), high-sugar drinks (rapid reflux), and large portions of red meat or cruciferous vegetables (slow gastric emptying compounds GI side effects). Adequate protein + soluble fiber + hydration are the wins.

How long do GLP-1 side effects last?

Most GI side effects (nausea, constipation, reflux) peak in weeks 1-2 after each dose increase and resolve within 4 weeks. If you stay on a stable dose without further titration, side effects typically fade for ≥80% of patients by week 12.

Does Ozempic cause stomach paralysis (gastroparesis)?

GLP-1 medications delay gastric emptying as part of their mechanism — that is not stomach paralysis. True gastroparesis after GLP-1 use is rare and the absolute risk in pharmacovigilance data is small. Symptoms (severe nausea, vomiting, abdominal pain past week 8) warrant evaluation.

Side-effect deep dive

NAION (sudden vision loss) on GLP-1 medications

Non-arteritic ischemic optic neuropathy — sudden painless vision loss in one eye. A 2024 Mass Eye and Ear cohort found ~4× higher rate in T2D semaglutide users vs non-GLP-1 controls; FDA is monitoring. Rare in absolute terms but worth knowing the warning signs.

Why it happens

NAION is a stroke of the optic-nerve head — the blood supply to the front of the optic nerve fails. The proposed GLP-1 mechanism is a rapid drop in blood-glucose + blood-pressure altering optic-nerve perfusion in patients with pre-existing small-vessel disease (disc-at-risk anatomy, sleep apnea, prior NAION in the other eye). Causation is not established; the JAMA Ophthalmology 2024 study was retrospective and single-center, not an RCT.

How to manage it

1.Baseline dilated eye exam if you have diabetes, sleep apnea, or NAION in the other eye
2.Slower dose titration if you have small-vessel disease risk factors
3.Stop the drug and contact ophthalmology immediately if any eye symptom appears
4.Do not restart after a NAION event — the other eye is at elevated risk

When to call your prescriber

Sudden painless vision loss in one eye
Blurry or missing spot in central or peripheral vision that appears within hours
Vision loss on waking (typical NAION presentation)
Any new visual-field defect

Affected medications

For clinicians and researchers

This is the patient-facing summary. The full evidence stack — Hathaway JAMA Ophthalmology 2024, Danish nationwide replication, Novo Nordisk internal safety review, Grzybowski 2025 review, and FAERS Reporting Odds Ratio with notoriety-bias context — lives in the clinician-facing evidence review.

Read the clinician-facing evidence review →

Sources

Common questions readers ask

Does Ozempic cause hair loss?: Not directly. Hair shedding (telogen effluvium) is reported by some patients ~3 months into rapid weight loss — typical of any rapid-weight-loss state, not unique to GLP-1.
What foods should you avoid on a GLP-1?: Avoid greasy, fried, and ultra-processed foods (worst nausea), high-sugar drinks (rapid reflux), and large portions of red meat or cruciferous vegetables (slow gastric emptying compounds GI side effects). Adequate protein + soluble fiber + hydration are the wins.
How long do GLP-1 side effects last?: Most GI side effects (nausea, constipation, reflux) peak in weeks 1-2 after each dose increase and resolve within 4 weeks. If you stay on a stable dose without further titration, side effects typically fade for ≥80% of patients by week 12.
Does Ozempic cause stomach paralysis (gastroparesis)?: GLP-1 medications delay gastric emptying as part of their mechanism — that is not stomach paralysis. True gastroparesis after GLP-1 use is rare and the absolute risk in pharmacovigilance data is small. Symptoms (severe nausea, vomiting, abdominal pain past week 8) warrant evaluation.

Editorial information based on FDA-label prevalence data + AERS pharmacovigilance + patient-reported outcome corpora. Not personal medical advice.