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Feeling drunk without alcohol? Gut bacteria may be to blame

Researchers uncover how changes in gut microbes can lead to alcohol production inside the body.

3 min readNew DelhiUpdated: Jan 16, 2026 10:17 AM IST

It has also been difficult to diagnose ABS; the most reliable method is closely monitored blood alcohol testing, which is not always available or easy to set up. (Image: Freepik)

For a small number of people, feeling drunk has nothing to do with drinking alcohol. Instead, it starts in the gut. In individuals with auto-brewery syndrome (ABS), a rare condition that causes the body to produce its own alcohol, scientists have now found more convincing evidence explaining how this occurs.

Certain gut bacteria and biological processes can convert common carbohydrates into ethanol, the same kind of alcohol found in beer or wine, according to researchers studying the illness. Once produced, that alcohol enters the bloodstream and can make a person appear intoxicated, even though they haven’t consumed any alcohol at all, according to a research paper published in Nature.

Auto-brewery syndrome is incredibly uncommon and frequently misdiagnosed. Many people suffer from the illness for years before getting a proper diagnosis due to low awareness and confusing symptoms. It has also been difficult to diagnose ABS; the most reliable method is closely monitored blood alcohol testing, which is not always available or easy to set up.

They may face major challenges during that time, such as health problems, social stigma, and even legal issues related to unexplained intoxication. Many patients now lack support and clear answers as a result.

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Researchers examined gut microbes from ABS patients, their household partners without the illness, and a different group of healthy people to better understand what causes the condition. Stool samples from ABS patients produced significantly more alcohol than samples from the other groups when tested during active symptom flare-ups. The result indicates that the stool sample tests may yield an easier and more valid diagnostic approach for ABS.

Additionally, the study helped to identify certain bacteria that are found to be associated with ABS, including Klebsiella pneumoniae and Escherichia coli. The notion of gut flora change being the primary cause for alcohol production is further supported by an increase in fermentation-associated enzymes in patients during flare-ups. Researchers indicate that it remains challenging to make an accurate identification of the exact microbes present in each patient.

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In one closely observed case, a patient who had struggled with symptoms saw significant improvement after receiving a faecal microbiota transplant, a treatment designed to restore healthy gut bacteria. Earlier treatments had not worked. Changes in gut bacteria closely matched periods of relapse and recovery, reinforcing the biological basis of the condition. After a second transplant using a different antibiotic approach, the patient showed no symptoms for more than 1.5 years.

Researchers believe that these findings could mark a breakthrough. By accurately identifying the bacteria and pathways involved, scientists hope to improve ABS diagnosis, expand treatment options, and reduce the stigma and confusion experienced by many patients.

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