GLP-1 Drugs Linked to Rare Brain Disorder in New Study

Researchers identified 15 cases of Wernicke encephalopathy tied to severe vitamin B1 deficiency in patients taking semaglutide or tirzepatide.

A study published in the journal *Clinical Nutrition* identified 15 cases of Wernicke encephalopathy — a rare, potentially fatal brain disorder caused by severe vitamin B1 (thiamine) deficiency — among people taking GLP-1 medications. Eight cases involved semaglutide, the active ingredient in Ozempic and Wegovy, while six involved tirzepatide, found in Mounjaro and Zepbound. Most of the cases were reported during 2023 and 2024, and thirteen of the fifteen cases came from the FDA's Adverse Event Reporting System, with one from published medical literature and one from the researchers' own medical center.

Instead, the concern is a chain reaction: the medications suppress appetite and slow digestion, and thirteen of the fifteen patients had experienced serious gastrointestinal or nutritional problems, including vomiting, significant appetite loss, malnutrition, or rapid weight loss. According to the New York Post, researchers examined 195,979 cases before identifying the 15 affected patients. The New York Post also reports that most patients with Wernicke encephalopathy showed gastrointestinal issues that can contribute to thiamine deficiency. The risk appears concentrated in people whose eating drops sharply while symptoms persist, rather than across all users of the drug class.

Wernicke encephalopathy is traditionally associated with three warning signs: mental confusion, problems with balance or walking, and abnormal eye movements. Yet only two of the fifteen patients in the study displayed the complete triad, making the condition easy to mistake for dementia, intoxication, or routine medication side effects. Baller Alert reports that among the eleven patients with follow-up information available, seven experienced lasting neurological complications. According to the New York Post, as many as 80% of cases go undiagnosed, some identified only at autopsy, and without treatment the condition can be fatal in up to 20% of cases while as many as 85% of survivors develop permanent brain damage.

The study does not establish that GLP-1 medications directly caused the cases. Because the analysis relies largely on adverse event reports, it cannot prove cause and effect or determine how often the condition occurs among the millions of people on these drugs. Clinician Karthik Achari told Fox News Digital, as reported by WOWO, that fifteen cases 'out of millions of people on these medications' means 'this is rare — but it's real, it's serious, and the mechanism makes sense.' The stakes remain high because early thiamine replacement, often intravenous, can stop the damage, and untreated deficiency can progress to permanent memory impairment and Korsakoff syndrome.

Researchers urged clinicians to watch for Wernicke encephalopathy in patients on semaglutide or tirzepatide, and additional studies are needed to clarify the relationship between GLP-1 drugs, nutritional deficiencies, and the disorder. Experts stress patients should not stop prescribed medications on their own, but should contact a health care provider promptly if they experience persistent vomiting, difficulty eating or drinking, unusual confusion, balance problems, or vision changes. Nutritionist Erin Palinski-Wade told Fox News Digital, per WOWO, that adequate nutrition and hydration are part of taking GLP-1s safely: 'Don't assume every side effect is just part of being on a GLP-1.' People with bariatric surgery history or heavy alcohol use face elevated thiamine-deficiency risk.