You've done everything right: timed your meals, taken post-dinner walks, filled your plate with nutritious foods, and even resisted the tempting donuts in the pantry. So why are you still bloated, gassy, and nauseous?
You might be dealing with a condition called SIBO, or small intestinal bacterial overgrowth.
In this guide, we’ll discuss SIBO, its symptoms, causes, and how to manage it. If you’re looking to regain control of your gut health, you’ve come to the right place.
What is SIBO, and why does it matter?
Your body contains trillions of bacteria, and most of these reside in the large intestine or colon. In a healthy gut, the small intestine has far fewer bacteria [1].
SIBO occurs when bacteria, usually found in the colon, grow in large numbers in the small intestine. When these bacteria digest carbohydrates from food, they produce gas, causing uncomfortable symptoms.
Common SIBO symptoms:
- Bloating or feeling overly full (especially after eating)
- Stomach cramps or discomfort
- Difficulty passing stools, constipation, or infrequent bowel movements
- Excess gas, leading to burping or flatulence
- Loose or watery stools, sometimes alternating with constipation [2]
SIBO affects up to 13% to 35% of otherwise healthy people [3]. It is often underdiagnosed and could be a root cause for those who present with conditions such as Irritable Bowel Syndrome (IBS) and inflammatory bowel disease (IBD) [4],[5].
SIBO vs. IMO
When SIBO symptoms are coupled with high levels of a microbe named Methanobrevibacter smithii, it may indicate a related condition, intestinal methanogen overgrowth (IMO) [6].
While SIBO is bacterial overgrowth in the small intestine, IMO involves the overgrowth of methane-producing microbes in any part of the digestive tract. Some practitioners refer to IMO as methanogenic SIBO.
Both conditions can be hard to diagnose because their symptoms—like bloating, constipation, and abdominal discomfort—overlap with other gut issues, such as food intolerances, irritable bowel syndrome (IBS), or celiac disease.
What causes SIBO?
Your gut has natural defenses against bacterial overgrowth—think of it as a security system. This includes gastric acid and bile, which break down harmful bacteria, along with proteolytic enzymes that digest unwanted invaders. Peristalsis—your gut's natural "wave-like motion"—keeps things moving, while secretory IgA acts like a first-line antibody defense. Finally, the ileocecal valve ensures bacteria from the colon don’t backtrack into the small intestine [7].
When the system fails, problems arise. Now let’s dive in further to the main SIBO causes.
Poor gut motility (gastroparesis)
Your stomach and intestinal muscles naturally work together to push food through the digestive tract. In gastroparesis, these muscles weaken and slow down, causing food to move too slowly, creating an opportunity for bacteria to grow [8]. In other words, poor gut motility can lead to SIBO.
Drugs that reduce gut motility may also increase SIBO risk. These include:
- GLP-1 drugs [9]
- Opioids [10]
- Anticholinergics [11]
Stress also reduces gut motility [12], and anything that causes food to linger in the small intestine has the potential to encourage bacterial overgrowth [13]. Once SIBO develops, it can worsen nutrient deficiencies and increase inflammation, which may intensify mental health symptoms, creating a vicious cycle.
Underlying chronic conditions
Certain pre-existing health conditions can increase the risk of SIBO by affecting gut motility, digestion, or bacterial balance.
You’re more likely to develop SIBO if you also have:
- Celiac disease [14]
- Crohn’s disease [15]
- Diabetes [16]
- Hypothyroidism [17]
- IBS [18]
- Liver cirrhosis [19]
- Obesity [20]
- Pancreatitis [21]
- Scleroderma [22]
Low stomach acid
While stomach acid often gets a bad rap, it’s actually very important for your health. It breaks down food, activates enzymes that turn proteins into amino acids and kills unfriendly bacteria that could make you ill. Low stomach acid, or hypochlorhydria, can be a major problem as it impairs digestion and reduces your body’s ability to moderate bacterial growth.
A common reason your stomach acid could be low is taking antacids or Proton Pump Inhibitors (PPIs) [23]. These medications reduce your stomach acid, which normally helps control bacterial growth, and this can contribute to SIBO.
Helicobacter pylori infection also increases the odds of developing SIBO, because H. pylori reduces the amount of acid your stomach makes [24].
Finally, having gastric bypass surgery can also affect your stomach acid production. SIBO develops in 29% of patients within three years of gastric bypass surgery [25]. In addition, intestinal surgeries can create "blind loops" where bacteria stagnate and grow [7].
Long-term effects of SIBO:
SIBO doesn’t just affect your gut—it can lead to nutrient deficiencies, chronic discomfort, and even systemic health problems.
In fact, SIBO can cause poor absorption of essential nutrients, like proteins, carbohydrates, and essential fatty acids [26]. This may lead to long-term health issues, such as:
- Low iron and vitamin B12 levels which often lead to weakness, weight loss, or anemia [26].
- A damaged gut lining (leaky gut) which can allow harmful substances into the bloodstream, triggering inflammation [27].
- Brain fog, mood swings, and worsened mood disorders like anxiety and depression [28].
- Skin issues, such as acne, rosacea, and psoriasis [29],[30],[31].
Bottom line, if you’re experiencing symptoms of SIBO, talk to your healthcare provider. Taking action now can reduce the likelihood of future health conditions.
How is SIBO diagnosed?
If you’ve been dealing with chronic bloating, irregular bowel movements, or unexplained digestive discomfort, it might be time to explore SIBO tests with your practitioner.
Breath testing
A breath test is a simple, non-invasive test that measures hydrogen or methane gas levels in your breath after you consume a sugar solution (like glucose or lactulose) [32]. When bacteria in your small intestine ferment these sugars, they produce gases that enter your bloodstream and are exhaled.
The glucose breath test is ideal for detecting overgrowth in the upper small intestine, where SIBO often begins [33]. A Lactulose test is useful for identifying overgrowth throughout the small intestine, though it carries a higher risk of false positives [34]. Talk to your practitioner about which test is right for you.
How breath testing works
Before taking a breath test, you’ll need to follow guidelines from your practitioner to prepare so the results are as accurate as possible. According to Cleveland Clinic, the preparation starts weeks before the test [35]:
- One month before: Stop taking antibiotics and probiotics.
- One week before: Stop taking laxatives, fiber supplements, antacids, and prokinetics.
- One day before: Limit your diet to only low-fiber, easily digested foods such as baked or boiled fish or poultry with salt and pepper. Your practitioner will typically recommend you avoid oils, fats, sweeteners, seasonings, dairy, and grains (except white bread and white rice). A strict diet without fermentable foods is crucial [36].
- Day of the test: No food or water for 12 hours. You’ll be asked to avoid exercising or sleeping within a few hours of the test.
The test itself usually takes 2 to 3 hours. Here’s what to expect:
- Your practitioner will collect a baseline breath sample.
- You’ll drink a special sugary drink (a solution of glucose, lactulose, or xylose—sugars that gut bacteria ferment).
- Your practitioner takes samples of your breath periodically.
- The samples are analyzed for the presence of hydrogen and methane.
What the results mean: hydrogen vs. methane
During your breath test, a rise in hydrogen or methane indicates bacterial overgrowth.
- Hydrogen: A rise in hydrogen (≥20 ppm within 90 minutes) typically indicates SIBO.
- Methane: A methane value of ≥10 ppm in your baseline sample or within 120 minutes of starting the test typically indicates IMO [37].
Challenges of breath testing
Breath testing, while widely used, has a few limitations:
- False Positives: Sugars moving too quickly to the large intestine can trigger misleading results.
- False Negatives: Slow digestion or low bacterial activity may fail to show overgrowth.
- Accuracy Issues: Factors like gut transit time or improper preparation can affect results [38], [32].
This said, breath testing remains the most practical and widely available tool for diagnosing SIBO and IMO, an important first step toward healing.
Duodenal aspirate culture
Another form of test for SIBO or IMO is a duodenal aspirate culture. During an upper endoscopy, a health practitioner directly samples fluid from your small intestine to check for bacterial overgrowth [39]. While this test is considered more accurate than a breath test, it’s invasive and rarely used in routine practice.
New diagnostic tools
Researchers are developing new swallowable capsule technology to improve SIBO testing [40]. One type of capsule measures hydrogen and carbon dioxide levels in the body after eating carbohydrates, offering a more accurate alternative to breath tests. Another type collects bacteria directly from the small intestine, providing a clearer and more precise evaluation of SIBO.
These advancements may enhance the accuracy and reliability of SIBO diagnosis in the future, paving the way for more effective treatments.
Managing SIBO: Approaches to healing
If you’re struggling with gut issues, understanding what’s causing the imbalance is essential. Food sensitivities, certain medications, and lifestyle habits could all be contributing factors. Let’s start by discussing how SIBO is typically treated, followed by strategies you can take to get to the root cause and support your gut health long-term.
Antibiotic therapy for SIBO
Oral antibiotics are a key for SIBO treatment [41]. The goal of antibiotics is not to completely eliminate bacteria but to reduce and balance them in the small intestine to relieve symptoms.
Several antibiotics, including amoxicillin with clavulanic acid, ciprofloxacin, doxycycline, and metronidazole, have been studied for SIBO treatment [42]. However, repeated antibiotic use carries risks of antibiotic resistance, recurrence, gut imbalances, and infections like Clostridium difficile.
Rifaximin has emerged as a preferred treatment option for SIBO due to its benefits:
- Studies show that rifaximin successfully resolves SIBO in 71% of cases [43].
- Unlike other antibiotics, rifaximin acts like a eubiotic, targeting specific microbes while supporting beneficial bacteria like Lactobacillus and Bifidobacterium [44].
- Rifaximin doesn’t lead to bacterial resistance, making it suitable for repeat use [45].
Testing your gut microbiome
When managing SIBO, a good place to start is addressing its root cause. An Adult Gut Health Test gives a holistic picture of your gut microbiome and may identify imbalances contributing to your SIBO or other gut issues. Your Gut Health Report provides deep insights, such as:
- Gut diversity: A diverse range of gut bacteria is a sign of better overall health, as more of the right species support a stronger, more balanced microbiome.
- Beneficial bacteria: Identifying bacteria that help boost metabolism and fight inflammation, which is key to gut and overall wellness.
- Disruptive microbes: It can also identify potential problems, like unfriendly pathogens or bacteria that degrade the gut’s protective mucus layer.
Every Tiny Health test comes with a personalized Action Plan with recommendations for diet, supplements, and lifestyle changes to help re-balance your disrupted gut. A coaching session with a microbiome specialist helps you navigate the results and your next steps, keeping in mind the symptoms you’re experiencing.
Dietary approaches to manage SIBO
What you eat directly impacts bacterial growth and fermentation in your gut. By carefully choosing foods, you can reduce symptoms like bloating, gas, and discomfort while healing your gut over several months. Let’s explore some key approaches for managing SIBO through diet.
Low-FODMAP diet
FODMAP stands for fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. This diet eliminates fermentable carbs like fructose, lactose, and sugar alcohols, which feed bacteria in the small intestine [46]. By limiting these, gas production and bloating are significantly reduced.
Choosing prebiotic foods wisely
Prebiotic foods nourish beneficial bacteria, but for people with SIBO, certain prebiotics can worsen symptoms by overfeeding bacteria in the small intestine. Careful moderation is key.
These SIBO-friendly prebiotic foods offer nutrients and support gut health without excessive fermentation:
- Green bananas and plantains contain resistant starch that feeds good bacteria without causing gas [47].
- Unripe papaya provides digestive enzymes and minimal fermentable fibers [48].
- Kiwi offers fiber and enzymes, often well-tolerated in small amounts [49].
- Zucchini, cucumbers (seedless), and carrots are sources of soluble fiber that are less likely to cause bloating [50].
- Flaxseeds are rich in omega-3 fatty acids and soluble fiber, which support the gut lining without overfeeding bacteria [51].
Avoid high-FODMAP foods and those rich in insoluble fiber, which can worsen SIBO symptoms, including:
- Onions and garlic (especially raw or whole).
- Asparagus, artichokes, and brussels sprouts.
- Legumes like lentils and chickpeas.
- Fruits such as apples, pears, and watermelon.
Elemental diet
The elemental diet is a liquid diet containing pre-digested nutrients that “starves” harmful bacteria while still providing essential nutrition. It’s often used short-term for severe cases to offer quick symptom relief [52].
Bi-phasic diet
The bi-phasic diet is a phased approach that starts by strictly reducing bacterial fuel and gradually reintroducing foods to assess tolerance [53]. Eating smaller, well-spaced meals also supports digestion and improves gut motility.
Fiber management
Not all fiber is created equal. Soluble fiber dissolves in water, forming a gel-like substance that’s gentler on digestion. Insoluble fiber adds bulk to stool but can worsen fermentation and symptoms in SIBO.
Tailoring fiber intake to your needs is important [54]—some may benefit from reducing fiber, while others may tolerate specific types that don’t trigger gas.
By focusing on foods that are easier to digest and being mindful of potential triggers, you can better manage SIBO symptoms and work toward a healthier, balanced gut.
Supplements for SIBO
Finding the right supplements can help you address deficiencies, support digestion, and promote gut healing. Here are some supplements your practitioner may recommend:
- Digestive enzymes help with proper food breakdown, especially if pancreatic enzyme production is low [55].
- Probiotics like Lactobacillus and Bifidobacterium may help support gut balance [56].
- Peppermint oil and ginger can help improve gut motility and reduce discomfort [57],[58].
- Gut-healing nutrients like L-glutamine and zinc support the repair of the stomach and intestine lining and help reduce inflammation [59],[60].
Take control of your digestive health
SIBO can really take a toll on your daily life, but understanding it is the first step to finding healing. It’s important to talk with a health practitioner if you are experiencing ongoing symptoms so you can find the right SIBO test and treatment plan.
Take control of your digestive health and get to the root cause of symptoms like bloating, gas, and constipation. Discover a science-backed approach to long-lasting relief with a Tiny+ membership, which includes a gut health test to establish your baseline, a coaching session with a microbiome specialist, and a follow-up gut health test to track your progress. This is your sign to take action, get to know your gut microbiome, and make changes to your diet and lifestyle to help soothe your gut, helping you get back to feeling like yourself again.
