A new study has flagged a rare but serious brain condition, Wernicke encephalopathy, in a small number of people taking GLP-1 weight-loss drugs such as Ozempic, Wegovy, Mounjaro and Zepbound. The disorder is caused by severe deficiency in vitamin B1, which can occur when reduced appetite and side effects like vomiting lead to inadequate nutrition, and researchers say cases appeared more frequently among GLP-1 users than those on other medications, though they stress this does not prove the drugs caused the condition. Experts consulted say the findings matter because, left untreated, the condition can cause permanent neurological damage or death, even though it remains uncommon given the millions of people using these medications.

The study, published in Clinical Nutrition, identified 15 cases via the FDA's Adverse Event Reporting System, medical literature and researchers' own clinical records, with most patients reporting gastrointestinal symptoms such as vomiting, appetite loss or malnutrition beforehand. Clinicians quoted in the article note that those at higher risk include people with persistent nausea and vomiting, rapid weight loss while eating very little, a history of bariatric surgery, or heavy alcohol use, and they advise anyone with symptoms such as confusion, balance problems or vision changes to seek medical attention promptly. Experts and the researchers themselves emphasise that patients should not stop taking prescribed GLP-1 medications based on this study alone, and are calling for further research to clarify any causal link.