A rare, serious brain condition may be linked to a small number of people taking GLP-1 weight loss and diabetes drugs, reports The Independent.
Around 15 cases of Wernicke encephalopathy were identified between 2023-2024 in an Israeli study’s review of the US Food and Drug Administration’s adverse event reports and related literature – the potentially life-threatening neurological disorder caused by a severe vitamin B1 deficiency that can lead to permanent memory loss and an inability to form new memories.
Experts said this condition is not common.
“Out of millions of people taking these medications, this is rare. The researchers went through adverse event reports and the medical literature and found only 15 cases of Wernicke encephalopathy in people taking GLP-1 drugs,” said Karthik Achari, a Chicago-based clinician who was not involved in the study.
“But it’s real, it’s serious, and the mechanism makes sense,” he added.
Most of the 15 cases – 13 in all – were reported in people who were suffering gastrointestinal side effects from the drugs, like vomiting and diarrhoea, and loss of appetite, the researchers wrote.
Vitamin B1, which supports the nervous system and brain health, only comes from food and supplements.
Around 11% of US adults, or about 30m, now take GLP-1 drugs for weight loss, according to a Gallup poll.
The majority of the cases in the study occurred with those drugs made with the active ingredients semaglutide or tirzepatide.
The findings suggest that patients on the drugs who experience more intense gastrointestinal side effects may be at an increased risk for Wernicke encephalopathy.
However, the researchers noted that FDA reports cannot prove the GLP-1 medications caused the condition. More research is needed to do that and the scientists were clear that patients should not stop taking prescribed GLP-1 drugs based on the study alone.
Past research has also discovered possible links between a small number of GLP-1 drug users and the brain condition.
“We noticed that patients weren’t just losing weight; they were also experiencing severe gastroparesis and persistent vomiting,” Dr Manar Kadhem, from Egypt’s Mansoura University, wrote in the research published in April.
Immediate treatment is necessary to prevent the worst outcomes from Wernicke encephalopathy.
“Emergency treatment with thiamine is essential. It may relieve symptoms and prevent permanent damage to memory and other brain functions,” said the Cleveland Clinic.
Study details
Glucagon-like peptide-1 receptor agonists and Wernicke encephalopathy: A pharmacovigilance study and literature review
Dana Lev, Avshalom Leibowitz, Alon Lang et al.
Published in Clinical Nutrition in February 2026
Summary
Background & aims
Glucagon-like peptide-1 receptor agonists (GLP-1 RAs) have revolutionised the treatment of type 2 diabetes mellitus and obesity in recent years. While gastrointestinal adverse events are common, their association with nutritional deficiencies, including thiamine, has not been comprehensively investigated. This study aimed to evaluate whether treatment with GLP-1 RAs is associated with the occurrence of Wernicke encephalopathy (WE).
Methods
We conducted a pharmacovigilance study using the FDA Adverse Event Reporting System (FAERS) and a narrative literature review. Disproportionality analysis assessed WE reporting following GLP-1 RA treatment using the reporting odds ratio (ROR) and the lower bound of the information component (IC) 95 % credibility interval.
Results
We identified 15 cases of GLP-1 RA-associated WE: 13 from FAERS, one from published literature, and one from our medical centre. Most cases occurred with semaglutide (n = 8/15) or tirzepatide (6/15), and were reported in 2023–2024 (14/15). Most patients (13/15) reported gastrointestinal manifestations of either weight loss, vomiting, loss of appetite, or malnutrition. Classic WE symptoms were reported in 11 patients, and the full clinical triad in 2 patients. Long-term neurological sequelae were noted in 7 of 11 patients with follow-up data. Disproportionality analysis showed increased reporting of WE with GLP-1 RAs compared with other medications (ROR = 2.35 [95%CI, 1.38–4.01]; IC025 = 0.29).
Conclusions
WE is a potentially rare but severe adverse event of GLP-1 RA treatment, mainly with semaglutide or tirzepatide. As early detection may prevent neurological sequelae, increased clinical awareness is warranted, especially in individuals experiencing severe gastrointestinal symptoms.
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