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What are the Common Symptoms of SIBO?
Updated on June 26, 2023
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What are the Common Symptoms of SIBO?
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SIBO, or Small Intestinal Bacterial Overgrowth, is a condition marked by abnormal growth in the population of bacteria in the small intestine.1

About 1,000 organisms/mL typically inhabit the upper small intestine. Most of them are Gram-positive. In SIBO, this number increases, ballooning to about 100,000–1,000,000 organisms/mL

Dr. Rizza Mira, our in-house medical expert

It is also known as Small Bowel Bacterial Overgrowth or SBBO.

A variety of factors can cause bacterial overgrowth. The most common factor is alteration in gut immune function and changes in bowel motility. Together, this leads to more bad bacteria overpopulating the good ones.

SIBO mainly affects the gut, causing digestive symptoms like stomach pains after eating, gas, bloating, etc. It can also cause more severe and chronic health problems if left untreated.

Risk Factors and Causes of SIBO

Several factors can increase your risk of developing SIBO. Some of them are defects in the structure and function of the digestive tract.  

Other factors are related to medications or lifestyle habits. The most common risk factors and causes of SIBO include:1

  • Gastric motility issues, such as gastroparesis or irritable bowel syndrome (IBS)
  • Use of certain medications, like proton pump inhibitors (PPIs) and narcotic pain medications2
  • Abdominal surgeries or bowel obstruction
  • Celiac disease, Crohn's disease, or other inflammatory bowel diseases
  • Immunodeficiency disorders, such as HIV/AIDS or common variable immunodeficiency (CVID)3
  • Diabetes, mainly when it results in nerve damage or delayed gastric emptying (gastroparesis)
  • Small bowel diverticulosis or the presence of small pouches (diverticula) in the small intestine lining. They can trap bacteria, leading to overgrowth4

If you have any of these risk factors, discussing them with your healthcare provider is essential. They will consider these details in determining the best action to prevent or treat SIBO.

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Most Common SIBO Symptoms

Gastrointestinal (GI) Symptoms

SIBO symptoms often mimic those of other digestive disorders, making diagnosing difficult. Common symptoms include:5

  • Abdominal pain
  • Abdominal distension
  • Bloating
  • Constipation
  • Diarrhea
  • Gas
  • Indigestion
  • Nausea

These symptoms can be caused by excess gas production and changes in bowel motility, suggesting bacterial overgrowth in the small intestine.

The intensity and duration of these symptoms can vary depending on the severity of your condition. 

“More severe symptoms can be attributed to a larger number of bacterial populations,” says Dr. Mira. 

SIBO may also resemble many other GI conditions or are caused by them.

Nutrient Malabsorption and Deficiencies

Nutrient malabsorption and deficiencies are also signs of SIBO. 

The primary role of the small intestines is to absorb nutrients from foods. However, conditions like SIBO can disrupt the absorption of essential nutrients. 

Fat Malabsorption and Diarrhea

The excess bacteria in the small intestines break down the bile salts, which usually are needed to digest fats. It can result in poor digestion of fats and diarrhea.1 

Damage to the Mucous Lining and Impaired Nutrient Absorption

These bacteria may also produce harmful byproducts that can damage the small intestine's mucous lining.5 

“They also induce an inflammatory response that can lead to fatigue and weakness, among other things,” says Dr. Mira.

It can impair the absorption of carbs and proteins, which are essential for maintaining overall health.

Nutrient Deficiencies

Studies show bacterial overgrowth can compete with the body for available food and deprive it of essential nutrients.6 

Malnutrition and Weight Loss

Malnutrition and weight loss can result from the combination of the above factors:

  • Bacterial competition for nutrients
  • Impaired absorption
  • Diarrhea

Fatigue and Other Non-Gastrointestinal Symptoms

SIBO primarily affects the GI system. It causes localized symptoms like abdominal pain, bloating, gas, etc. 

However, SIBO can manifest in more systemic ways, impacting your overall health and well-being. 

The bacterial overgrowth can trigger an inflammatory response in the small intestine. The reaction produces many symptoms linked to SIBO, such as:

  • Joint pain
  • Skin inflammations
  • Brain fog

Nutrient deficiencies, inflammation, and other factors might contribute to these symptoms in people with SIBO.

How is SIBO Different from IBS?

Small Intestinal Bacterial Overgrowth (SIBO) and Irritable Bowel Syndrome (IBS) are both gut-related conditions. They can sometimes be interchanged due to the overlap in their symptoms.

However, they are different in terms of their causes and the areas of the digestive system they affect. 

SIBO is marked by an overgrowth of bacteria caused by an imbalance in the small intestinal bacterial population. This includes certain bacteria types that aren't typically in the small intestine

The exact causes of SIBO remain unclear, but different factors may contribute to its development, such as:

  • Structural problems in the gut
  • Low small bowel motility
  • Certain medical conditions (e.g., Crohn's disease, Parkinson's disease, diabetes)
  • Low stomach acid levels

On the other hand, IBS affects the large intestine. The exact cause of IBS is unknown, but most attribute it to be immune-mediated. An interplay of several factors, such as stress, diet, and imbalances in the gut microbiome, also increases the risk.7

How Can I Tell if My Symptoms Indicate SIBO or IBS?

SIBO and IBS share overlapping symptoms (abdominal pain, bloating, gas, constipation, and diarrhea). But health experts can clinically verify and treat bacterial overgrowth.

A diagnostic process helps them distinguish if the symptoms you’re experiencing indicate SIBO or  IBS. 

When diagnosing SIBO, your doctor will measure your breath's hydrogen and methane concentrations using breath tests.8 

The test is a non-invasive way to help trace the presence of bacterial overgrowth in the small intestine. However, some cases need an invasive procedure such as an endoscopy. 

“However, there are no exact studies that support one diagnostic modality as the gold standard for SIBO. This is an evolving illness,” says Dr. Mira.

On the other hand, IBS is a functional GI disorder. Experts can only diagnose it when a clinically known cause cannot explain the symptoms.9

Your doctor will likely use the Rome IV criteria for IBS diagnosis. To diagnose IBS, you must have had recurrent abdominal pain for at least one day per week in the last three months. 

It must be associated with two or more of the following:9

  • Pain related to defecation
  • A change in the frequency of stool
  • A change in the form (appearance) of stool

Additionally, before an IBS diagnosis, your doctor will rule out other potential causes of your symptoms. It includes infections, inflammatory bowel disease, or celiac disease. 

The key differences between the SIBO and IBS diagnostic procedures are the methods used and the focus of the test. 

This distinction in diagnostic methods helps doctors separate between the two conditions. It can also help provide appropriate treatment.

In cases when you have both SIBO and IBS simultaneously, diagnosis and treatment can be more complicated. 

If you suspect you have both, you must consult a healthcare professional for a thorough assessment. They can offer appropriate guidance on your treatment options and how to manage your condition. 

How is SIBO Diagnosed and Treated?

Doctors diagnose SIBO through non-invasive tests such as breath tests or more invasive procedures like endoscopy. 

Treatment typically involves antibiotics and dietary changes. In some cases, doctors also give medications to improve gut motility.

Diagnosis and Testing

Doctors typically recommend SIBO testing if you experience chronic or long-term symptoms. Currently, the methods used to diagnose SIBO are the following:

Breath Testing

The bacteria in the small intestine produce hydrogen or methane when they react with sugar. These gases expand the small intestine, causing familiar symptoms like bloating, burping, gas, discomfort, and so on.10

“Breath testing is more favored than other diagnostic methods because it is non-invasive and is easier to perform,” says Dr. Mira.

Your body absorbs these bacteria into the bloodstream. Once they reach your lungs, the body emits them through your breath. 

Two types of breath tests are used to diagnose SIBO: the lactose and the glucose breath tests. 

  • Lactulose breath tests involve checking your breath routinely after you take a sugary drink called lactulose. The presence of hydrogen before hitting the 90-minute mark indicates SIBO. 
  • The glucose breath test involves ingesting a glucose solution instead. The small intestine absorbs glucose more rapidly, making this test less sensitive. However, it may not effectively detect SIBO in the distal small intestine. But a positive glucose breath test can still indicate bacterial overgrowth in the small intestine. 

Your healthcare provider will determine which breath test suits your situation more.


In the past, the gold standard for SIBO testing was the small intestine aspirate and fluid culture. To perform this test, doctors insert a long, flexible tube called an endoscope down your throat.1 

They'll navigate the endoscope through your upper digestive tract until it reaches the small intestine. 

“This method is helpful if ulcerations along the gastrointestinal tract (called Peptic Ulcer Disease) are considered,” says Dr. Mira.

Next, a fluid sample is aspirated or collected. It will be cultured and analyzed in the lab to determine the presence of bacterial overgrowth

However, research suggests that the small intestine aspirate and fluid culture method may only detect a small percentage of the microbiota in the small intestine.11,12 

It’s because SIBO can occur inconsistently throughout the small intestine. In addition, the aspirate might not accurately measure overgrowth in areas far from the test site.

Moreover, some bacterial species within the small intestine could be more challenging to culture effectively. 

Due to these limitations, this method has become less commonly used in clinical practice to diagnose SIBO.

Stool Testing

Stool testing can detect some signs of SIBO. It can uncover fat malabsorption and bacterial composition changes in the colon

But it's not considered a reliable method for diagnosing SIBO. The significant difference between the large and small intestines environments reduces the reliability of stool tests for SIBO detection.

“Some invasive gastrointestinal tract infections can also produce the same symptoms as SIBO. In this case, stool testing is the most useful method,” says Dr. Mira.

Treatment Options

The standard treatment options for SIBO include antibiotics, dietary changes, and probiotics.


Antibiotic therapy is currently the leading approach to lessen small intestine bacterial overgrowth. 

It is also believed that antibiotics address malabsorption by alleviating the inflammation in the small intestine lining.

SIBO has two types: 

  • Methane-dominant SIBO, which usually results in constipation
  • Hydrogen-dominant SIBO, which causes diarrhea

Doctors prescribe antibiotics to treat both SIBO types. But, you may need to include fiber in your diet when treating methane-dominant SIBO. 

The primary antibiotic treatment for SIBO sometimes varies. This can include broad-spectrum antibiotics, Rifaximin, and/or Metronidazole, which kills different bacteria strains to help improve your condition. Studies show that most people respond positively to this treatment.13

Dietary Changes

Changing your diet is a crucial part of managing SIBO. It can help regulate the bacterial balance in your intestine. 

By avoiding foods that trigger symptoms, you can effectively manage symptoms and other issues related to SIBO.

Additionally, dietary changes can help address nutritional deficiencies caused by SIBO. It ensures that your body receives the necessary nutrients.


Probiotic supplements contain beneficial bacteria. They can help restore a healthy balance of gut flora after antibiotic treatment. 

However, the use of probiotics for SIBO is still being studied. But some research suggests they may help reduce symptoms and prevent the recurrence of SIBO

How Can I Manage My SIBO Symptoms Through Diet?

You can help manage your SIBO symptoms through a diet that eliminates specific carbs and includes gut-friendly foods. 

This diet promotes a balanced gut microbiome and may help alleviate discomfort.

FODMAP Diet and Other Diets

A low-FODMAP (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) diet can be beneficial in reducing symptoms of SIBO.14 

It can relieve discomfort due to symptoms, help improve gut health, and potentially prevent the recurrence of your symptoms. 

Low-FODMAP diet limits the consumption of carbs that are difficult to digest and ferment in the gut. It was designed to manage the symptoms of IBS.  

“Difficult-to-digest carbohydrates produce more gas that can worsen your symptoms,” says Dr. Mira.

When customizing a low-FODMAP diet for SIBO flare-ups, focus on avoiding the primary categories, such as:

  • Fructose: Simple sugars commonly found in fruits, certain vegetables, honey, and agave nectar
  • Lactose: A sugar molecule present in dairy products
  • Fructans: A sugar compound found in gluten products, fruits, some vegetables, and prebiotics
  • Galactans: A compound found in specific legumes
  • Polyols: Sugar alcohols often used as sweeteners in various products

In SIBO, inflammation in the small intestine lining may lead to poor absorption of two FODMAP types—lactose and fructose

In addition, gut bacteria improperly located in the small intestine may ferment other non-absorbed FODMAPs. It leads to bloating and various digestive symptoms.

A low-FODMAP diet can benefit those with SIBO by limiting carbohydrate intake and depriving the small intestinal bacteria

“The first step of this diet is eliminating high FODMAP foods. The next steps are slow reintroduction to see which ones you can hardly tolerate,” says Dr. Mira.

However, it's important to note that no clinical studies have been conducted on this subject so far.

Alternative Dietary Approaches for SIBO

The low-FODMAP diet is the most commonly recommended dietary approach for managing your symptoms. 

Other alternative diets, such as the Specific Carbohydrate Diet (SCD) and the GAPS diet, can be helpful to some people.15

SCD focuses on removing complex carbs and emphasizing easily digestible, nutrient-dense foods. It restricts the consumption of grains, lactose, and certain sugars

The GAPS diet is designed to improve gut health and has been used by some people to manage SIBO. It focuses on consuming nutrient-dense, easily digestible foods like bone broths, fermented foods, and organic meats

It aims to eliminate grains, refined sugars, and processed foods.

Foods to Avoid and Foods to Include

When there’s an excessive presence of bacteria in your small intestine, they get to benefit from the foods you eat first before your body. 

These bacteria produce gas as they use your food for fuel, which leads to discomfort and bloating

Consider avoiding foods that have higher amounts of FODMAPs, such as:

  • High-fructose corn syrup
  • Agave nectar
  • Honey
  • Soda and soft drinks
  • Apples
  • Dried fruits
  • Flavored yogurt
  • Ice cream
  • Garlic
  • Onions
  • Asparagus
  • Butternut squash
  • Cauliflower
  • Artichokes
  • Barley
  • Rye
  • Grains
  • Beans
  • Peas
  • Sausage
  • Sweetened cereals

A SIBO diet may appear restrictive since it limits different types of food. But you can still consume plenty of food while following this temporary diet plan. The elimination part of the diet typically ranges from two to six weeks. 

A SIBO-friendly diet focuses on foods that are high in fiber and low in sugar, such as:

  • Protein foods: Beef, pork, lamb, chicken, turkey, duck, fish, shellfish, eggs, milk
  • Plant-based protein foods: Tofu, tempeh, unsweetened peanut butter, unsweetened almond butter, nuts, and seeds (1oz or less per serving)
  • Grains and Cereals: Gluten-free crackers, oatmeal, unsweetened cereal (made from low FODMAP grains), rice or gluten-free noodles, quinoa
  • Vegetables: Spaghetti squash and summer squashes, broccoli (heads only, less than 3/4 cup), leafy greens, carrots, potatoes, pumpkin
  • Fruits: Blueberries, grapes, oranges, strawberries

When Should I See a Doctor for My SIBO Symptoms?

It’s essential to seek appropriate medical care for SIBO symptoms when they persist or worsen or if they significantly impact your quality of life. 

If you’re experiencing the following issues, it’s time to consult a doctor for proper diagnosis and treatment:

  • Persistent GI symptoms, such as abdominal pain, bloating, excessive gas, diarrhea, or constipation that don't improve with over-the-counter remedies or dietary changes
  • Unintentional weight loss or fatigue
  • Nutritional deficiencies despite eating a balanced diet
  • If your symptoms return or worsen after an initial improvement

An accurate diagnosis can help identify the underlying cause and implement the appropriate treatment plan. 

Additionally, proper treatment can help prevent complications such as malabsorption, nutritional deficiencies, and other long-term health issues.

Remember, self-diagnosis and self-treatment may not always be safe. It's best to consult with a healthcare professional to ensure you receive the appropriate care for your specific needs.

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Updated on June 26, 2023
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15 sources cited
Updated on June 26, 2023
  1. Small intestinal bacterial overgrowth (SIBO).” Mayo Clinic.
  2. What are the effects of proton pump inhibitors on the small intestine?” World Journal of Gastroenterology.
  3. Small bowel bacterial overgrowth and immunodeficiency.” American Academy of Allergy Asthma and Immunology.
  4. Diverticular Disease of the Stomach and Small Bowel.” MSD Manual.
  5. Small Intestinal Bacterial Overgrowth.” Gastroenterology and Hepatology.
  6. Uninvited Guests: The Impact of Small Intestinal Bacterial Overgrowth on Nutritional Status.” Nutrition Issues In Gastroenterology.
  7. Irritable bowel syndrome (IBS).” NHS Inform.
  8. 4 Best Ways To Test For SIBO.” Integrative Naturopathic Medical Centre.
  9. Rome Criteria and a Diagnostic Approach to Irritable Bowel Syndrome.” Journal of Clinical Medicine.
  10. Symptoms & Causes of Gas in the Digestive Tract.” NIH: National Institute of Diabetes and Digestive and Kidney Diseases.
  11. Small intestinal bacterial overgrowth syndrome.” World Journal of Gastroenterology.
  12. Retained Surgical Foreign Bodies after Surgery.” Open Access Macedonian Journal of Medical Sciences.
  13. Preferential usage of rifaximin for the treatment of hydrogen-positive small intestinal bacterial overgrowth.” Scielo.
  14. Low fermentable oligosaccharides, disaccharides, monosaccharides, and polyols diet in children.” World Journal of Clinical Cases.
  15. SIBO Diets - GAPS diet and SCD.” IBS Diets.
Cristine Santander
Cristine Santander
Content Contributor
Cristine Santander is a content writer for KnowYourDNA. She has a B.S. in Psychology and enjoys writing about health and wellness.
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