IAFTC Newsletter. Volume 2. Issue 2. July, 28, 2026.

Andrew D. Ewens, PhD, DABT¹

¹5000 Centregreen Way, Suite 500, Cary, NC 27513. 

Andy.E@ToxicologistExpert.com 

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This is an open-access article under the CC BY-NC-ND license.

Abstract

A new study was published in the journal Obesity [1,2] that reviewed six case reports of patients who were taking GLP-1 drugs and who developed thiamine (Vitamin B1) deficiency and Wernicke's encephalopathy. The classic triad symptoms of Wernicke’s encephalopathy (confusion, nystagmus, and ataxia) can be mistaken for acute alcohol intoxication or as an indication of chronic alcohol use disorder. Of the six patients, five had confusion, delirium, and memory loss, five had nystagmus, and four had ataxic gait disturbances. 

The patients also had GI problems of nausea, vomiting, anorexia, and constipation, which can be caused by both Wernicke’s encephalopathy and are common side effects of GLP-1 agonists. This overlap of symptoms and side effects may complicate diagnosis. Despite treatments with thiamine supplementation, one patient died, four developed irreversible Korsakoff syndrome symptoms, and only one patient fully recovered.

Introduction

Thiamine is an enzymatic cofactor for several enzymes involved in cellular energy production and other metabolic processes (pyruvate dehydrogenase, alpha-ketoglutarate dehydrogenase, branched-chain alpha-keto acid dehydrogenase, and transketolase) [1,2,3,4]. Thiamine deficiency can inhibit glycolysis feeding into the Krebs cycle, leading to lactic acidosis, which can cause brain damage detectable by MRI. Thiamine deficiency is frequently seen in people who have chronic alcohol use disorder due to poor diet and a reduction in thiamine absorption by the intestines. People who take GLP-1 agonist drugs likely develop thiamine deficiency due to their decreased food intake. Additional risks for thiamine deficiency include bariatric surgery, GI disorders, fasting, pregnancy, lactation, malignant disease, diabetes, hemodialysis, systemic infections, AIDS, and renal failure. 

Thiamine is a water-soluble vitamin that does not greatly accumulate in the body, with only limited storage in the liver and other organs [3,5]. Thiamine is rapidly eliminated in the urine, so that daily intake is needed to prevent deficiencies. Because of its low toxicity and accumulation, excess intake of thiamine is well tolerated. Continuous loss of thiamine dietary intake can lead to deficiency in a matter of weeks. Urine thiamine concentrations can indicate daily intake levels. However, detecting deficiencies is less simple, and blood concentrations can be misleading. A measure of erythrocyte transketolase activity provides a more accurate indication of deficiency. Because of the added complexity of blood testing, many cases of deficiency go undiagnosed. 

Thiamine deficiency can cause the condition beriberi, which can produce cardiac failure, edema, lactic acidosis, GI problems, and peripheral neuropathy with symptoms of sensory, motor, and reflex impairment [1,2,3,4]. Prolonged thiamine deficiency can result in Wernicke’s encephalopathy, which commonly causes a triad of symptoms of confusion, ataxic gait, and ocular movement problems, such as nystagmus and ophthalmoplegia. Wernicke’s encephalopathy can be fatal or can progress to Korsakoff syndrome (Korsakoff psychosis) with irreversible memory loss, confusion, and delirium. Treatment of acute disease by thiamine supplementation is usually aggressive and administered intravenously rather than orally due to limitations of intestinal absorption. Early treatment is needed to prevent irreversible damage to the brain.  

What does this mean for you?

GLP-1 agonist drugs can greatly impact the toxicological evaluation of legal cases involving alleged alcohol impairment. It is already known that GLP-1 agonist drugs prolong alcohol absorption by slowing gastric emptying and movement along the gastrointestinal tract. This can cause an expansion of the onset of the elimination phase to almost 6 hours [5,6]. This prolonged onset of reaching the elimination phase can invalidate attempts at calculating a retrograde extrapolation to determine a BAC at the time of driving based on an alcohol test performed after driving. Furthermore, the fasting state produced by these GLP-1 drugs can raise concerns about ketosis, which has the potential to interfere with breath alcohol test results [6].

Now, with this newly published study [1,2], it appears GLP-1 agonist drugs can also impact toxicological evaluations in additional ways by causing thiamine deficiency. The symptoms of Wernicke’s encephalopathy can be mistaken for acute alcohol intoxication (confusion, nystagmus, and ataxia) and could also be mistaken for an indication of chronic alcohol use disorder.

These are just case reports, but the widespread use of GLP-1 agonists is very new and only growing. Be sure to ask your attorneys if their clients are taking these medications and if they have any diagnosed medical conditions.  

Bibliography

[1] Bhattacharya S., semaglutide linked to rare brain illness, Medscape Medical News MedBrief, July 14, 2026. https://www.medscape.com/viewarticle/semaglutide-linked-rare-brain-illness-2026a1000npa?ecd=a2a 

[2] Bidesie, J., Oudman E., Wernicke’s encephalopathy following semaglutide treatment for obesity: A systematic PRISMA review of case-based evidence, Obesity, 0:1-6, 2026. https://doi.org/10.1002/oby.70256

[3] Martel J., Doshi H., Sina R. E., Franklin D. S., Vitamin B1 (Thiamine), StatPearls, StatPearls Publishing, Updated Jan 31, 2024. https://www.ncbi.nlm.nih.gov/books/NBK482360/

[4] Mrowicka M., Mrowicki J., Dragan G., Majsterek I, The importance of thiamine (Vitamin B1) in humans, Bioscience Reports, 43: BSR20230374, 2023. https://doi.org/10.1042/BSR20230374

[5] Ewens A., GLP-1 agonist drug influence on alcohol absorption, IAFTC Annual Conference, International Association of Forensic Toxicology Consultants, May 29, 2026. https://doi.org/10.21428/7c9a8daa.6b5b11ae   

[6] Semenoff J. Semaglutides, Liraglutides & Ketone Production: Can use as a weight loss medication create false-positive breath testing results? Counterpoint: The journal of science and the law, 7(3):1, Updated June 2025. https://www.counterpoint-journal.com/vol-7-iss-2-art-6-semaglutides-and-ketoacidosis.html 

Competing Interests

Andrew D. Ewens, PhD, DABT, is a forensic toxicology consultant and provides expert testimony in civil and criminal cases.