A rare and potentially fatal brain disorder has been reported in people using weight loss medications, according to a new study.
Wernicke encephalopathy is a neurological condition marked by severe confusion and disorientation. Without prompt treatment, the symptoms can continue to worsen.
The disorder is caused by a deficiency of thiamine, also known as vitamin B1. Found in foods including meat, fish and whole grains, the nutrient is essential for healthy brain function.
In cases not associated with GLP-1 medications, patients are typically middle-aged and have an alcohol use disorder, which can disrupt the body’s ability to absorb nutrients. Other intestinal conditions that impair nutrient absorption can also lead to the disease.
However, researchers in Israel have now identified 15 reported cases of Wernicke encephalopathy in people taking GLP-1 drugs.
Eight patients had been taking semaglutide, the active ingredient in Ozempic and Wegovy, before their diagnosis. Six were using tirzepatide, found in Zepbound and Mounjaro, while one patient had been taking liraglutide, the active ingredient in the older weight loss drug Saxenda.
The patients had an average age of 59 and had used the medications for roughly five months before developing Wernicke encephalopathy. All reported other symptoms, including gastrointestinal problems.
Dr Dana Lev, an internal medicine specialist at Sheba Medical Center and the study’s first author, and her colleagues wrote: ‘Wernicke encephalopathy is a potentially rare but severe adverse event of [weight loss drug] treatment.
Scientists have warned that weight loss drugs may be linked to Wernicke encephalopathy, a neurological disorder that causes severe confusion and disorientation
‘As early detection may prevent [progression], increased clinical awareness is warranted, especially in individuals experiencing severe gastrointestinal symptoms.’
The research found an association but did not establish that weight loss drugs cause the potentially deadly brain disorder.
Nevertheless, the findings may serve as an important warning for clinicians, who are being encouraged to remain alert to the possibility that patients could develop the condition.
Most of the cases analyzed came from the FDA’s Adverse Event Reporting System, a database used to report suspected medication side effects.
Reports submitted to the system are not verified, as anyone can file one. It is intended to function as a basic early-warning system for possible drug-related side effects.
The study, published in the journal Clinical Nutrition, found that difficulty walking and confusion were the most frequently recorded symptoms before diagnosis. Seven patients experienced each of these symptoms.
Abnormal mental status and paralysis or weakness of the eye muscles were the second most common, each reported in three patients.
Before the patients were diagnosed with the condition, six reported suffering from vomiting, while five suffered from decreased appetite and malnutrition and three suffered from gastroparesis, or paralysis of the stomach.
The condition is caused by a lack of vitamin B1, a vital nutrient for the functioning of the brain
Almost all the cases reported in the study occurred during the reporting year 2023 to 2024. One was recorded during the reporting year 2017 to 2018.
Ten were recorded in the US, while two each were in Europe and Asia and one was reported in South America.
Of the nine patients with prescription information available, four had been prescribed weight loss drugs for their diabetes, three had been prescribed them for weight loss and two had been prescribed them for both weight loss and diabetes.
Eight of the cases were reported by clinicians, while four were reported by healthcare providers and three by consumer attorneys.
It was not clear what may have caused the patients to develop the condition, but the researchers said it could be linked to deficiencies.
They wrote: ‘The prominent weight loss associated with [weight loss drug] treatments alongside the relatively frequent gastrointestinal side effects provides a biologically plausible basis for our findings and suggests increased susceptibility to nutritional deficiencies, including thiamine depletion.’
Although vitamin B1 is vital for the body, it cannot make it itself – instead humans rely on animal and plant sources to ensure a sufficient intake.
Almost everyone gets enough of this vitamin from a standard diet, but weight loss drug users often consume significantly less food than others, putting them at risk of vitamin and mineral deficiencies.
They may also have gastrointestinal problems, which affect nutrient absorption, and vomit regularly, which also reduces the amount of vitamins their body absorbs, raising the risk of deficiencies.
Wernicke encephalopathy has already been linked to patients who undergo bariatric surgery, which can cause malnutrition because a patient cannot eat standard meals for six to eight weeks after the procedure.
Estimates suggest up to 18 percent of bariatric surgery patients develop some degree of vitamin B1 deficiency, raising the risk of suffering from the neurological condition.
Scientists noted, however, that the 15 cases among weight loss drug users were reported out of the millions already taking the medication.
Estimates suggest 30 million Americans have used a weight loss drug at least once to date, equivalent to 11 percent of the population.
Doctors say people with Wernicke encephalopathy have three main symptoms: confusion, inability to coordinate movements and visual changes.
If these symptoms are left untreated, they cause lasting damage to brain and nerve cells, leading to a second condition, Korsakoff syndrome, which causes severe memory loss and the inability to form new memories.
The condition is fatal because it raises the risk of injury and incapacity, which can be life-threatening. It also leaves an individual unable to look after themselves.
Studies suggest up to two percent of people worldwide suffer from Wernicke encephalopathy, although it isn’t clear how many people may have the condition in the US.
Doctors can slowly reverse symptoms of the condition by administering vitamin B1 as pill supplements or injections.
If someone has suffered brain damage already due to the condition, however, they will not be able to completely cure the condition.
Counseling for alcohol use disorder or nutritional support can help to prevent the disease.
