GLP-1 Drugs Linked to 15 Reported Cases of Wernicke Encephalopathy, Study Finds
A new study identified 15 reports of Wernicke encephalopathy among people taking GLP-1 medicines. Here is what researchers found, what remains uncertain, and which warning signs patients should know.
GLP-1 medicines have become increasingly common in the treatment of type 2 diabetes, obesity, and related health conditions. Drugs containing semaglutide and tirzepatide can help reduce appetite and food intake, making them an important part of treatment for many patients.
A new study has drawn attention to a rare neurological disorder called Wernicke encephalopathy among people taking GLP-1 receptor agonists. The research identified 15 reported cases involving patients who were being treated with medicines in this drug class.
However, the findings do not establish that GLP-1 medicines caused the neurological condition. Instead, researchers say the reports highlight a potential safety issue that may deserve greater awareness, particularly among patients experiencing prolonged vomiting, substantial weight loss, or inadequate nutritional intake.
What Did the Study Find?
The study, published in the journal Clinical Nutrition, examined reports of Wernicke encephalopathy associated with GLP-1 receptor agonists.
Researchers identified 15 cases. Fourteen of those reports occurred between 2023 and 2024. Thirteen came from the U.S. Food and Drug Administration's Adverse Event Reporting System, while one was identified through previously published medical literature and another came from the researchers' own medical center.
Semaglutide was involved in eight cases, while tirzepatide was involved in six. Semaglutide is the active ingredient in medicines including Ozempic and Wegovy. Tirzepatide is marketed under names such as Mounjaro and Zepbound.
The study also reported that 13 patients experienced at least one gastrointestinal or nutritional issue. These included vomiting, reduced appetite, malnutrition, and weight loss.
Among the 11 patients for whom follow-up information was available, seven experienced long-term neurological complications, according to the researchers.
These numbers are important, but they need to be interpreted carefully. The study involved reports of adverse events rather than a controlled clinical trial designed to determine whether the medications caused Wernicke encephalopathy.
What Is Wernicke Encephalopathy?
Wernicke encephalopathy is a serious neurological disorder caused by a deficiency of thiamine, also known as vitamin B1.
Thiamine plays an important role in the body's energy metabolism and is particularly important for normal brain function. When the body does not have enough of the vitamin, neurological problems can develop.
The condition is traditionally associated with three major symptoms: changes in mental status, problems with coordination or walking, and abnormal eye movements.
However, patients do not necessarily experience all three symptoms. The National Library of Medicine notes that the classic combination is present in only a minority of cases, meaning that the condition can be difficult to recognize.
Other possible symptoms include confusion, dizziness, difficulty concentrating, memory problems, abnormal eye movements, and problems maintaining balance.
Because untreated Wernicke encephalopathy can result in serious and potentially permanent neurological damage, early recognition and treatment are important.
Why Are GLP-1 Medicines Being Discussed?
The researchers highlighted a possible connection between some known effects of GLP-1 medicines and conditions that can contribute to thiamine deficiency.
GLP-1 medications can reduce appetite and food intake. They can also cause gastrointestinal side effects.
For example, the current FDA prescribing information for Ozempic lists nausea, vomiting, diarrhea, abdominal pain, and constipation among its most common adverse reactions. The prescribing information also warns about severe gastrointestinal adverse reactions.
The FDA prescribing information for Zepbound similarly lists nausea, diarrhea, vomiting, constipation, abdominal pain, and other gastrointestinal reactions among its commonly reported adverse reactions.
Researchers therefore proposed that prolonged vomiting, reduced food consumption, substantial weight loss, or poor nutritional intake could potentially contribute to thiamine depletion in certain patients.
This is a proposed biological pathway, however, rather than proof that the medications directly cause Wernicke encephalopathy.
The Study Does Not Establish Cause and Effect
One of the most important points for patients is that adverse-event reports cannot by themselves demonstrate that a particular medicine caused a medical condition.
The FDA's adverse-event reporting system collects reports of health problems that occur after medicines are used. Such reports can be valuable for identifying possible safety signals, but they may contain incomplete information.
There may also be other explanations for a patient's illness, including underlying medical conditions, nutritional deficiencies, rapid weight loss, prolonged vomiting, or other medications and treatments.
The researchers themselves described Wernicke encephalopathy as a potentially rare but serious adverse event and called for increased clinical awareness rather than concluding that GLP-1 drugs directly cause the disorder.
The study also noted that only two of the 15 patients had the complete traditional combination of altered mental status, impaired coordination, and abnormal eye movements. Eleven patients had at least one of those symptoms.
Who Is at Risk of Thiamine Deficiency?
Wernicke encephalopathy is most commonly associated with chronic alcohol misuse, but alcohol is not the only risk factor.
According to the National Library of Medicine, severe malnutrition, prolonged vomiting, bariatric surgery, pregnancy-related vomiting, certain illnesses, and other conditions affecting nutrition can also contribute to thiamine deficiency.
This broader understanding is particularly relevant when evaluating patients who experience major changes in food intake.
For someone taking a GLP-1 medicine, persistent vomiting or an inability to eat adequately should therefore be discussed with a healthcare professional rather than ignored.
Warning Signs Patients Should Recognize
Patients using GLP-1 medicines should be aware of significant or persistent symptoms, particularly when they occur alongside poor food intake or substantial weight loss.
Potential warning signs of Wernicke encephalopathy include:
- New or unexplained confusion
- Significant changes in mental status
- Difficulty walking or maintaining balance
- Abnormal or uncontrolled eye movements
- Severe weakness associated with poor nutritional intake
- Prolonged vomiting or inability to maintain adequate food intake
These symptoms can have many possible causes, and experiencing one of them does not mean a person has Wernicke encephalopathy.
Nevertheless, sudden neurological symptoms require prompt medical assessment.
What Should Patients Do?
People taking semaglutide, tirzepatide, or another GLP-1 medicine should not stop a prescribed medication solely because of this study without first speaking with their healthcare provider.
Instead, patients experiencing persistent vomiting, significant difficulty eating, rapid or substantial weight loss, confusion, walking problems, or unusual eye movements should contact a medical professional promptly.
Wernicke encephalopathy is considered a time-sensitive condition. Current medical references emphasize prompt treatment with parenteral thiamine when the condition is suspected because delaying treatment can increase the risk of lasting neurological complications.
The new study does not mean that most people taking GLP-1 medicines are at risk of developing this disorder. Rather, it raises a question that researchers say deserves further investigation.
As use of GLP-1 medicines continues to expand, monitoring nutritional status and recognizing unusual neurological symptoms may become increasingly important areas of clinical care.
Sources
- PubMed, Clinical Nutrition study: Wernicke encephalopathy associated with GLP-1 receptor agonists, PubMed record 41534460.
- National Library of Medicine, NCBI Bookshelf: Wernicke Encephalopathy, updated January 2026.
- U.S. Food and Drug Administration: Current Ozempic prescribing information, revised May 2026.
- U.S. Food and Drug Administration: Current Zepbound prescribing information, revised February 2026.
Medical Disclaimer
This article is provided for general informational and educational purposes only and is not medical advice. Patients should speak with a qualified healthcare professional about their individual symptoms, nutritional needs, treatment options, and medication decisions. Do not start, stop, or change a prescribed medication without appropriate medical guidance.