What is SIBO? Symptoms, Diagnosis, and Treatment

SIBO, or small intestinal bacterial overgrowth , is a gastrointestinal disorder. Although it's not classified as a distinct condition, it can be truly disruptive to daily life and negatively impact health. Unfortunately, patients with endometriosis are more susceptible to it. Furthermore, some symptoms are similar, which can complicate accurate diagnosis. That's why we decided to break down this topic. This article is a compendium of knowledge about SIBO that will help you better understand this problem and learn how to manage it.

What is SIBO?

SIBO (small intestinal bacterial overgrowth) is a type of dysbiosis, or a disorder affecting the gut microbiota. Microbiota refers to all the microorganisms that inhabit the intestines. You've likely heard of it before – it's become a hot topic in recent years, and each month brings new scientific reports on its impact on the body. The health of the gut microbiota is the foundation of overall health. It influences inflammation, immunity, metabolism, digestion, and absorption, and even communicates with the nervous system and affects brain function. Microbiota primarily inhabits the large intestine, and the number of microorganisms in the small intestine is tightly controlled. However, sometimes, bacteria overgrow in the small intestine, and this condition is called SIBO.

The bacteria that inhabit our intestines engage in fermentation processes daily. This produces certain vitamins (e.g., vitamin K) and short-chain fatty acids (e.g., butyric acid) with regenerative and anti-inflammatory properties. However, a side effect of fermentation is the production of gases, including hydrogen, methane, and carbon dioxide. Under physiological conditions, our bodies can handle this without causing any discomfort. However, when the intestines are over-colonized with bacteria, increased fermentation and gas production occur, resulting in the most characteristic symptom of SIBO: severe, persistent bloating, resembling a pregnant belly .

It's estimated that SIBO affects approximately 20% of the population, but this figure may be underestimated. This is due, in part, to diagnostic difficulties and the fact that just a few years ago, no one had heard of SIBO. The problem is still often downplayed, with bloating and other gastrointestinal symptoms treated solely as a consequence of excessive stress. Some patients are still told that it's just their appearance. However, remember that SIBO isn't just about bloating. Untreated overgrowth can cause digestive and malabsorption problems, nutritional deficiencies and their consequences, damage to the intestinal villi, and increase the risk of other gastrointestinal problems. If you feel your intestines aren't functioning as they should, seek support from a specialist.

Where does SIBO come from?

SIBO doesn't just appear out of thin air. It always has a cause. Our bodies are physiologically equipped with defenses that protect us from the development of dysbiosis and bacterial overgrowth. However, under the influence of many environmental factors and diseases, these defense mechanisms weaken. There's been a lot of talk online about the causes of SIBO recently, but I'd like to warn you against blindly following all the information. Much of it has a very negative tone and is intended to scare the reader. Serious endocrine, neurological, and even cancer disorders are often cited as the main causes of SIBO. Of course, these can lead to SIBO, but more often than not, its causes are benign, simple, and we can address them ourselves. So remember not to self-diagnose and assume the worst-case scenarios. If you suspect SIBO, consult a doctor and a dietitian, who will guide you through the diagnostic process.

What are the possible causes of SIBO?

• Lack of so-called food hygiene SIBO can begin in the mouth. If you eat quickly, swallow large bites, or don't chew thoroughly, your digestive tract can't handle digestion. Leftover food remains in the intestines longer, promoting bacterial growth and excessive fermentation. 
• Frequent snacking – Meal breaks should be 3-4 hours. This is essential for the proper functioning of the MMC, or the so-called migratory myoelectric complex. I colloquially call it the "intestinal brush." ​​Its role is to cleanse the intestines of food debris. The highest activity of the MMC is observed approximately 2-3 hours after a meal. Snacking and eating more frequently than every 3 hours causes the digestive tract to accumulate too much food debris at once, which the MMC cannot handle. This, in turn, leads to excessive bacterial fermentation, bacterial colonization of the small intestine, and the development of SIBO. Taking care of the MMC is fundamental to the prevention and treatment of SIBO, as well as preventing its recurrence. 
• Gastric hypoacidity The stomach and its proper functioning are a key line of defense against bacterial overgrowth. An acidic environment, hydrochloric acid, and digestive enzymes neutralize bacteria and prevent them from reaching the small intestine. Hypoacidity, or a state of impaired hydrochloric acid production, can predispose to SIBO. Maintaining stomach health is crucial for both the prevention and treatment of SIBO. 
• Irritable bowel syndrome (IBS) IBS and SIBO very often co-occur, although it's not always possible to clearly determine which came first. However, IBS significantly increases the risk of SIBO due to factors such as its impact on intestinal peristalsis and visceral sensitivity. Both disorders are also closely linked to stress. You can read more about IBS in our article. "Irritable bowel syndrome." 
• Hypothyroidism – I don't know if you know this, but thyroid hormones not only affect thyroid function and fertility, but also determine the proper functioning of our intestines. A deficiency in thyroid hormones causes slower intestinal peristalsis, which in turn promotes the retention of food waste and the growth of bacteria. 
• Parasitic diseases – Parasites can disrupt the composition and diversity of the intestinal microbiota, as well as the functioning of the MMC complex. In the case of recurrent SIBO symptoms, it is recommended survey for parasitic infections. 

SIBO can also be caused by previous abdominal surgery, including cesarean section. Disturbances in the ileocecal valve, which is located between the small and large intestines, can also contribute to the development of SIBO. Its main function is to prevent the reflux of food and bacteria from the large intestine into the small intestine. As a result of previous surgery, the use of certain medications, or individual anatomical differences, its function may be impaired. 

SIBO and endometriosis

Endometriosis and SIBO often coexist, and the relationship between them is bidirectional. On the one hand, endometriosis increases the risk of SIBO. This is related to inflammation and the presence of endometrial foci and adhesions, which affect intestinal motility. On the other hand, SIBO can worsen the course of endometriosis and exacerbate its symptoms. Why does this happen? Dysbiosis is associated with increased production of inflammatory mediators. Additionally, SIBO can result in an excess of bacteria that produce beta-glucoronidase, an enzyme that inhibits the removal of estrogen from the body. Remember that endometriosis is an estrogen-dependent disease, so maintaining estrogen balance is crucial.

If you struggle with endometriosis and SIBO, you may want to consider our EndoBiotic , which contains probiotic bacteria and potent anti-inflammatory substances. It's best used after SIBO treatment.

Symptoms of SIBO

Bacteria that overpopulate the small intestine use food waste for fermentation, producing gases—hydrogen and/or methane. Their excessive production causes the most characteristic symptom of SIBO: severe abdominal bloating. This often persists throughout the day, regardless of food, stress, or physical activity. Some patients report that even after a glass of water, their stomach feels like a balloon. Additionally, bloating or constipation may occur. An overgrowth of hydrogen-producing bacteria ( hydrogen SIBO ) primarily causes diarrhea. However, an overgrowth of archaea ( methane SIBO ), i.e., methane-producing bacteria, causes constipation. Hydrogen-methane SIBO is also possible , with alternating diarrhea and constipation.

Additionally, SIBO can cause excessive gas, a feeling of heaviness and fullness, and intestinal gurgling. However, it's important to remember that the clinical presentation of SIBO can be highly variable. Due to the lack of specific symptoms, the presence of symptoms alone is only a guide for further diagnosis and does not necessarily determine the presence or absence of SIBO. 

Untreated and long-term SIBO can also cause nonspecific symptoms related to digestive and malabsorption disorders, and nutritional deficiencies. Patients with SIBO often struggle with deficiencies in iron, vitamin B12, and fat-soluble vitamins. Excessive hair loss, dry and pale skin, weakened immunity, and poor physical condition are common symptoms associated with SIBO.

SIBO diagnosis

SIBO poses a diagnostic challenge for both patients and specialists. The gold standard is duodenal aspiration and culture , but this test is highly invasive and difficult to access, so it is primarily used in clinical trials rather than in everyday medical practice. Patients suspected of SIBO are therefore referred for a hydrogen-methane breath test with lactulose . Its advantage is that it is noninvasive and painless, but its correct interpretation is very difficult. Furthermore, meticulous preparation is necessary to reduce the risk of false positive results.

What does the hydrogen-methane test involve? Here's how it works in a few steps:

1. Preparation for the examination. Before the test, you must follow a very strict diet for 24-48 hours. During this time, you are only allowed to eat cooked meat, fish, and eggs. No fruits, vegetables, carbohydrates, dairy products, or large amounts of fat are allowed. Additionally, you should discontinue all antibiotics and probiotics for approximately 4-6 weeks before the test, and avoid supplements and non-essential medications for 2-3 weeks. The test is performed in the morning. Before the test, you should refrain from brushing your teeth, chewing gum, eating, drinking, or exercising. 
2. Taking the first sample. First, a so-called zero breath sample is collected. Based on the results, it is possible to initially assess whether the test preparation was correct. 
3. Drinking lactulose solution. The patient then drinks a lactulose solution.
4. Sampling. During the test, breath samples are collected approximately every 20 minutes. The entire test takes approximately three hours. During this time, you should not eat, drink, or change position. 
5. Sample analysis: The concentration of hydrogen and methane in exhaled air is measured using a specialized analyzer. 

As you can see, this is a non-invasive and painless test, though quite tedious. Proper preparation is essential for reliable results – even the slightest deviation from the recommended diet before the test, or the introduction of medications or supplements, can completely distort the results. Interpreting the results is unfortunately not easy and should be performed by an experienced gastroenterologist with the support of a clinical dietitian. Do not self-diagnose or compare your results to others. The test results should be compared with the reported symptoms and approached comprehensively.

How to treat SIBO?

In SIBO treatment, a holistic approach and collaboration between multiple specialists are crucial: a physician, dietitian, physiotherapist, and psychologist. A combination of antibiotics and dietary therapy is most often used. Unfortunately, this is a lengthy process that can take up to several months and requires significant commitment from both specialists and the patient. In my experience, some of the main and most common causes of SIBO treatment failure are acting on your own and without a plan, the desire for quick results, excessive supplementation, and underestimating the role of both diet and lifestyle. Remember, self-care isn't a quick fix, and quick fixes aren't always beneficial. Health is our greatest asset and our most valuable resource. Take care of it wisely and don't entrust it to just anyone.

SIBO – drug treatment

The first stage of SIBO treatment is usually antibiotic therapy, which lasts 10-14 days. For some people, a single course is sufficient, but sometimes it needs to be repeated several times every 30 days. Rifaximin or a combination of rifaximin and neomycin is used to treat SIBO. Rifaximin has a eubiotic effect, meaning it restores the balance of the intestinal microbiota – it reduces bacterial overgrowth but also positively influences beneficial intestinal bacteria, so it doesn't lead to the sterilization of the microbiota like many other antibiotics. It acts locally, exclusively within the intestines, as it is not absorbed from the gastrointestinal tract, so it rarely causes side effects.

Low FODMAP Diet for SIBO

After completing antibiotic therapy, appropriate dietary therapy should be implemented. The most common is the low-FODMAP diet . Although this is the gold standard for IBS treatment, and research evaluating its use in SIBO is still limited, most patients with bacterial overgrowth experience significant improvement and symptom relief after implementing it.

The low-FODMAP diet involves limiting foods high in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. These components are most susceptible to fermentation by intestinal bacteria, increase osmotic pressure, and are poorly absorbed in the small intestine. Restricting these sources provides relief for many SIBO patients, but remember that the low-FODMAP diet is not a lifelong diet. It is a very strict dietary therapy protocol that should be followed in specific cases, for a specific period of time, in a specific manner, and under the supervision of an experienced specialist.

You can read more about the low FODMAP diet in our article " Low FODMAP diet and endometriosis – how and when to use it? "

Elemental diet for SIBO

The elemental diet is another dietary model that can be considered for SIBO. Unlike the low-FODMAP diet, its effectiveness in SIBO has been scientifically proven. However, it's worth emphasizing that this form of treatment is reserved for special cases and, in practice, is only used when other methods have failed.

What does an elemental diet involve? It involves administering special mixtures containing macronutrients in their most easily digestible form – amino acids instead of proteins, and simple sugars instead of carbohydrates. Additionally, the mixtures include all essential vitamins and minerals. Patients on an elemental diet consume special, medically prepared preparations rather than standard, self-prepared meals. This approach allows the intestines to "rest" and regenerate. In simple terms, an elemental diet leads to the starvation of intestinal bacteria, thus reducing their numbers.

When and how should you use the elemental diet for SIBO? It should be used for no longer than two weeks. It can be considered when antibiotic therapy has failed, in patients suffering from multiple allergies and food intolerances, and when SIBO is accompanied by other gastrointestinal diseases, especially inflammatory ones. Remember, this decision should never be made on your own. The elemental diet is relatively expensive (a 14-day treatment can cost up to several thousand zlotys) and must be carefully planned to avoid malnutrition and nutritional deficiencies.

Herbs for SIBO – what is worth using?

Herbal therapy for SIBO is a controversial topic. Theoretically, there are many herbs that could support SIBO therapy through their antibacterial, immunomodulatory, and digestive benefits. However, their practical application is uncertain, and there is still insufficient data to clearly confirm their effectiveness. Currently (September 2025), oregano, allicin, and berberine appear to be the most promising. 

• Oregano oil – contains carvacrol and thymol with strong antibacterial and antimicrobial properties, may support digestion by stimulating the production of bile, saliva and gastric juice. 
• Allicin (garlic extract) – allicin is a biologically active substance found in garlic cloves, which is called a natural antibiotic. 
• Berberine – has antibacterial and anti-inflammatory effects. Research results regarding its use in SIBO are promising, but unfortunately, it can cause side effects, so extreme caution is recommended. 

Prokinetics in SIBO 

Prokinetics are substances whose function is to support the functioning of the myoelectric complex (MMC). They facilitate the cleansing of the digestive tract from residual food, thus preventing excessive bacterial fermentation and gas production. Prokinetics for SIBO should be introduced after completing antibiotic therapy and continued throughout the treatment process. Ginger is a natural prokinetic . You can use it in the form of teas, ginger juice water, or simply by chewing ginger slices between meals.

Summary

SIBO is a condition in which the small intestine contains a higher than normal number of bacteria. The causes of SIBO are complex and may include environmental and hormonal factors. The clinical presentation is highly variable, but in most people, the predominant symptoms are bloating and changes in bowel habits. Unfortunately, diagnosing and treating SIBO are not easy, but with interdisciplinary collaboration between specialists and patient involvement, truly positive results can be observed.

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