Auto-Brewery Syndrome: Why Your Gut Can Make You Drunk Without a Single Drink — and How It's Treated

Medically reviewed by Dr. Baraa Alnahhal, MD. Last reviewed October 13, 2026. This content is for educational purposes and is not medical advice.

Quick Answer

Auto-brewery syndrome is a rare condition in which gut microbes ferment the sugars you eat into alcohol, making you intoxicated without drinking [1]. It results from an overgrowth of ethanol-producing yeasts or bacteria [1]. Symptoms resemble drunkenness and follow carb-heavy meals [1]. Treatment uses antibiotics or antifungals plus a reduced-carbohydrate diet [1]; most people recover, though it can return if triggers come back [1].

What the research says

• The evidence on auto-brewery syndrome is still small. A 2023 review screened the published medical literature and narrowed it to 24 relevant articles covering ABS’s epidemiology, causes, diagnostic difficulties, and management. The authors describe ABS as the gastrointestinal tract producing excessive endogenous ethanol, and they aimed to identify gaps in understanding to improve detection, treatment, and awareness (Paramsothy et al., Cureus, 2023) [5].

• Antifungal treatment ended symptoms in a well-documented case, and a prior antibiotic course may have set it up. In a case report with literature review, a man had fungal yeast forms in his upper small bowel and cecum, confirmed with a standardized carbohydrate challenge test followed by endoscopy. After antifungal treatment he could eat carbohydrates without symptoms. He had been exposed to a prolonged antibiotic course, which the authors postulated altered his gut microbiome and allowed fungal growth. He stayed on a carbohydrate-free diet for the first 6 weeks, and the authors noted the role of probiotics in this condition has not been studied (Malik et al., BMJ Open Gastroenterology, 2019) [4].

• Think of ABS when someone shows alcohol intoxication, has measured blood ethanol, and denies drinking. A case report described a patient with symptoms of intoxication and objectively elevated blood ethanol levels but no history of alcohol consumption. The authors link the syndrome to yeast overgrowth causing ethanol fermentation in the gut, and note that information on it in the medical literature is limited (Akhavan et al., ACG Case Reports Journal, 2019) [2].

What Is Auto-Brewery Syndrome?

Auto-brewery syndrome (ABS) is a rare condition that causes alcohol intoxication in people who haven’t consumed any alcohol [1] [2]. It’s also known as gut fermentation syndrome (GFS) [1] [4]. It happens when microbes in your intestines ferment the sugars that you eat to produce ethanol [1], just like a brewery in your gut.

We all have microbes living in our guts, usually harmlessly. Alcohol-producing bacteria and fungi like Saccharomyces cerevisiae (brewer’s yeast) are part of a normal gut microbiome [1]. They also produce small amounts of ethanol in all of us. A normal metabolism usually clears it before it reaches our bloodstream [1].

In auto-brewery syndrome, these microbes produce ethanol at a rate that exceeds your body’s capacity to clear it [1]. The excess alcohol in your bloodstream causes your blood alcohol content (BAC) to rise to intoxication levels. Yeast overgrowth, high blood sugar and impaired metabolism can all contribute [1].

How Rare Is Auto-Brewery Syndrome?

There are fewer than a hundred documented cases of auto-brewery syndrome [1], but most researchers suspect it’s more common than we know [1]. Low awareness of the condition makes it hard for people and their healthcare providers to recognize it. It can also be difficult to diagnose when they do suspect it.

What Are the Symptoms of Auto-Brewery Syndrome?

Auto-brewery syndrome causes alcohol intoxication, just like drinking alcohol does. The symptoms are subtler at lower levels. But as blood alcohol content (BAC) rises, they’ll more closely resemble what we know as “drunkenness.”

Milder symptoms might include brain fog, clumsiness, delayed reaction time, drowsiness, impaired judgment, memory issues, and reduced inhibitions [1].

More advanced symptoms can include agitation, balance issues, blurred vision, dilated pupils, flushed face, mood swings, vomiting, and slurred speech [1].

When you’re not intoxicated, you might have other symptoms, like abdominal pain, blackouts, bloating and gas, fatigue, food sensitivities, hangover, changes in your bowel habits, and runny nose or cough [1].

Symptoms of intoxication tend to follow meals and drinks high in carbohydrates, like pasta, potatoes and fruit juice [1]. The process can take up to 24 hours [1]. If you’re not aware of how this works, symptoms will seem to occur randomly. They can interfere with important social events and activities like driving.

What Causes Auto-Brewery Syndrome?

Auto-brewery syndrome happens when microbes living in your gut ferment the carbohydrates passing through it and produce ethanol, so much that it intoxicates your bloodstream, making you “drunk.” For this to occur, one or several things in your digestive system are out of balance or not working right.

There Are Too Many Ethanol-Producing Microbes in Your Gut

A healthy gut microbiome supports many different types of microorganisms, most of which are harmless, and many of which are helpful to us. The variety of microbes in your gut helps prevent any one type from overgrowing. But certain conditions can throw this balance off. This is called dysbiosis (an imbalance in your gut’s normal mix of microbes) [1].

In auto-brewery syndrome, an overgrowth of gram-negative bacteria or yeasts like Saccharomyces cerevisiae or Candida albicans causes an excess of fermentation in your gut [1]. Many different factors can contribute to gut dysbiosis, but the most significant ones are medications and medical conditions.

Contributing factors may include frequent or long-term use of antibiotics; gastrointestinal diseases that slow down the movement (motility) of your GI tract; higher blood sugar than average, providing more fuel for these microbes to ferment; and a weakened immune system due to medical conditions or medications [1].

You Aren’t Metabolizing Ethanol Effectively

Even normal, healthy guts produce small amounts of fermentation and alcohol (endogenous ethanol). But not much of it will ever reach your bloodstream. That’s because your liver takes the first pass at metabolizing the alcohol in your gut before the leftovers begin to accumulate in your blood [1].

But certain conditions can affect this first-pass metabolism. Some people have a genetic variation that impairs one of the enzymes you need to metabolize alcohol in your liver. Advanced liver disease can also impair your liver’s ability to metabolize alcohol. These conditions can sometimes contribute to ABS [1].

What Are the Risk Factors?

You might be more likely to develop auto-brewery syndrome if you have or have had a diet high in carbohydrates, alcohol intolerance, candidiasis (a yeast infection condition), cirrhosis of the liver, diabetes, metabolic dysfunction-associated steatotic liver disease (MASLD, formerly known as fatty liver disease), metabolic syndrome, or small intestinal bacterial overgrowth (SIBO) [1].

What Are the Complications?

Auto-brewery syndrome affects your body, brain and life just the way frequent alcohol use would. The potential complications are the same as those for alcohol use disorder [1]. Besides interfering with your relationships and job performance, frequent intoxication will affect your mental and physical health.

Complications can include accidents and injuries; blackouts, assaults and DUIs; brain damage; depression and suicidal thoughts; fetal alcohol syndrome; and liver disease [1].

Alcohol intoxication can be life-threatening at higher levels, when it becomes alcohol poisoning. This usually occurs at BAC levels over 0.30 [1]. Auto-brewery syndrome can cause these levels of intoxication, though it’s unlikely [1]. Alcohol poisoning is more of a risk for children and people with lower tolerance [1].

How Is Auto-Brewery Syndrome Diagnosed?

A healthcare provider might suspect auto-brewery syndrome if you have symptoms consistent with alcohol intoxication, an elevated blood alcohol content, and haven’t consumed alcohol [1] [4].

They’ll confirm these things through observation, discussion and testing. They’ll ask about your eating and drinking habits, then observe your symptoms and test them repeatedly over a period of time.

Tests might include a physical exam and other routine diagnostics; blood tests or breathalyzer tests for blood alcohol content (BAC); an oral glucose tolerance test to observe your response to carbohydrates; a hydrogen breath test to identify bacterial overgrowth; a stool test and culture to identify fungal overgrowth; and an endoscopy to take a fluid sample from your GI tract [1].

How Is Auto-Brewery Syndrome Treated?

First-line treatment for auto-brewery syndrome focuses on restoring balance to your gut microbiome. Your healthcare provider will prescribe antibiotics or antifungals to target the overgrowth [1]. Then, they’ll review your diet, reduce carbohydrates and sometimes make other personalized recommendations [1].

This approach works for most people [1]. But some people with severe dysbiosis might have a harder time rebooting their gut microbiomes. They might need a little extra support, like a personalized nutrition plan, targeted probiotics or treatment for other conditions contributing to auto-brewery syndrome [1].

What Foods Should You Avoid With Auto-Brewery Syndrome?

While living with and recovering from auto-brewery syndrome, your healthcare provider will advise you to cut back on carbohydrates (sugars and starches). These are the foods that feed the yeasts in your gut and provide fuel for fermentation. Reducing them will reduce fermentation and your yeast population.

Foods to avoid include white bread, white rice, potatoes, pasta, crackers and chips, fruit juice, milk, and anything with added sugar [1].

Can You Drive With Auto-Brewery Syndrome?

If you don’t know when symptoms of intoxication are going to pop up, you probably shouldn’t drive. But if you’re aware of your condition and how your eating habits affect it, you might be able to predict the cycle and schedule your driving around it. Hopefully, treatment will eventually make this unnecessary.

Is Auto-Brewery Syndrome Curable?

The treatment approach to auto-brewery syndrome is simple and straightforward, and it’s usually successful. But some people do have a harder time fixing it than others. Treatment also won’t necessarily cure ABS forever. If the conditions that caused it become active again, ABS could return [1].

How Can I Lower My Risk of Auto-Brewery Syndrome?

If you have one or more of the risk factors, you might want to take extra care of your gut health to help prevent dysbiosis. This begins with eating a good variety of plants and other whole foods, and reducing sweets and starches.

You can also make a point of adding probiotic and prebiotic foods to your diet to boost your gut flora, or ask your healthcare provider to recommend a good probiotic supplement. This is especially important if you’ve recently taken antibiotics or other medications that may have depleted your gut microbiome.

What Is Urinary Auto-Brewery Syndrome?

This lesser-known variation of auto-brewery syndrome occurs in your bladder instead of in your gut. It’s also called bladder fermentation syndrome [1]. In urinary ABS, fungal overgrowth in your urinary system feeds on excess sugars in your urine, producing alcohol in your pee that passes to your bloodstream [1].

What Questions Should I Ask My Healthcare Provider?

You may want to ask your provider what is causing your symptoms, whether your gut microbes could be fermenting the foods you eat, and what tests can confirm auto-brewery syndrome. Other useful questions include what foods you should avoid, whether antibiotics or antifungals are right for you, how long treatment usually takes, and what to do if symptoms return after treatment.

Conclusion: A Brewery in Your Gut, and a Simple Path Out

Auto-brewery syndrome is one of the strangest conditions in medicine: your own gut microbes ferment the carbohydrates you eat into enough ethanol to intoxicate you, without a single drop of alcohol. Fewer than a hundred cases have been documented, yet most researchers suspect the condition is more common than we know, because low awareness makes it hard for patients and providers to recognize.

The trigger is a gut imbalance called dysbiosis, usually an overgrowth of yeasts like Saccharomyces cerevisiae or Candida albicans, and the symptoms (drowsiness, slurred speech, blurred vision, mood swings) tend to follow high-carb meals and can take up to 24 hours to appear. The good news is that treatment is simple and usually successful: antibiotics or antifungals to target the overgrowth, plus a lower-carbohydrate diet to starve the fermenting microbes.

While ABS isn’t guaranteed to stay away forever, since it can return if the underlying triggers come back, most people get their gut back in balance and their life back on track. If you or someone you love experiences unexplained drunkenness after meals, don’t write it off as random: talk to a healthcare provider. Explore Rinnit.com’s library of gut health and digestive condition guides for more plain-language answers.

Frequently Asked Questions

What is auto-brewery syndrome? Auto-brewery syndrome (ABS) is a rare condition that causes alcohol intoxication in people who haven’t consumed any alcohol. Also called gut fermentation syndrome, it happens when microbes in your intestines ferment the sugars you eat to produce ethanol.

How does your gut make alcohol? Microbes in your gut, including brewer’s yeast (Saccharomyces cerevisiae), naturally ferment carbohydrates into small amounts of ethanol in everyone. Normally, your metabolism clears it before it reaches your bloodstream. In ABS, the microbes produce ethanol faster than your body can clear it, so your blood alcohol content rises to intoxication levels.

What are the symptoms of auto-brewery syndrome? Symptoms mimic drunkenness: brain fog, clumsiness, drowsiness, impaired judgment, reduced inhibitions, slurred speech, blurred vision, dilated pupils, flushed face, mood swings, agitation, balance issues and vomiting. Between episodes, you might have abdominal pain, blackouts, bloating, fatigue, food sensitivities, hangover, bowel changes, or a runny nose or cough.

When do symptoms appear? Symptoms of intoxication tend to follow meals and drinks high in carbohydrates, like pasta, potatoes and fruit juice. The process can take up to 24 hours, so if you’re not aware of how it works, symptoms can seem to occur randomly.

How rare is auto-brewery syndrome? There are fewer than a hundred documented cases, but most researchers suspect it’s more common than we know. Low awareness makes it hard for people and providers to recognize, and it’s difficult to diagnose even when suspected.

What causes auto-brewery syndrome? An overgrowth of ethanol-producing microbes (gram-negative bacteria or yeasts like Saccharomyces cerevisiae or Candida albicans), a condition called dysbiosis. Contributing factors include frequent or long-term antibiotic use, GI diseases that slow gut motility, higher-than-average blood sugar, and a weakened immune system. Impaired first-pass metabolism of alcohol in the liver (from a genetic variation or advanced liver disease) can also contribute.

Who is at higher risk? People with a diet high in carbohydrates, alcohol intolerance, candidiasis, cirrhosis of the liver, diabetes, metabolic dysfunction-associated steatotic liver disease (MASLD), metabolic syndrome, or small intestinal bacterial overgrowth (SIBO).

Can auto-brewery syndrome be fatal? Alcohol intoxication becomes life-threatening at high levels (alcohol poisoning), usually at BAC over 0.30. ABS can cause these levels, though it’s unlikely. Alcohol poisoning is more of a risk for children and people with lower tolerance.

What are the complications? The same as alcohol use disorder: accidents and injuries, blackouts, assaults and DUIs, brain damage, depression and suicidal thoughts, fetal alcohol syndrome, liver disease, and interference with relationships and job performance.

How is auto-brewery syndrome diagnosed? A provider suspects it when you have intoxication-like symptoms and elevated BAC despite not drinking alcohol. Tests may include blood tests or breathalyzer (BAC), oral glucose tolerance test, hydrogen breath test (bacterial overgrowth), stool test and culture (fungal overgrowth), endoscopy, and physical exam.

How is it treated? First-line treatment restores balance to your gut microbiome: antibiotics or antifungals to target the overgrowth, plus a review of your diet with reduced carbohydrates. Some people with severe dysbiosis may need a personalized nutrition plan, targeted probiotics, or treatment for contributing conditions.

What foods should you avoid with ABS? Carbohydrates (sugars and starches) feed the fermenting yeasts. Foods to avoid include white bread, white rice, potatoes, pasta, crackers and chips, fruit juice, milk, and anything with added sugar.

Can you drive with auto-brewery syndrome? If you don’t know when symptoms will appear, you probably shouldn’t drive. If you understand how your eating habits trigger symptoms, you may be able to predict the cycle and schedule driving around it, though treatment should eventually make this unnecessary.

Is auto-brewery syndrome curable? Treatment is simple and usually successful, but it won’t necessarily cure ABS forever. If the conditions that caused it become active again, ABS could return.

What is urinary auto-brewery syndrome? A lesser-known variation that occurs in your bladder instead of your gut, also called bladder fermentation syndrome. Fungal overgrowth in your urinary system feeds on excess sugars in your urine, producing alcohol in your pee that passes to your bloodstream.

References

1. Cleveland Clinic. Auto-Brewery Syndrome. Cleveland Clinic. Last updated April 22, 2025. https://my.clevelandclinic.org/health/diseases/auto-brewery-syndrome

2. Akhavan BJ, et al. Drunk Without Drinking: A Case of Auto-Brewery Syndrome. ACG Case Rep J. 2019;6(9):e00208. PMID 31750376. https://doi.org/10.14309/crj.0000000000000208

3. Kruckenberg KM, et al. Urinary Auto-brewery Syndrome: A Case Report. Ann Intern Med. 2020;172(10):702-704. PMID 32092761. https://doi.org/10.7326/L19-0661

4. Malik F, et al. Case report and literature review of auto-brewery syndrome: probably an underdiagnosed medical condition. BMJ Open Gastroenterol. 2019;6(1):e000325. PMID 31423320. https://doi.org/10.1136/bmjgast-2019-000325

5. Paramsothy J, et al. Understanding Auto-Brewery Syndrome in 2023: A Clinical and Comprehensive Review of a Rare Medical Condition. Cureus. 2023;15(4):e37678. PMID 37206535. https://doi.org/10.7759/cureus.37678

Medical Disclaimer

This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay seeking it because of something you have read here.