SIBO Symptoms: Is Bacterial Overgrowth Behind Your Bloating and Fatigue?

If you have been dealing with chronic bloating, unpredictable bowel habits, and fatigue that no one seems to be able to explain, you may have heard the term SIBO, or small intestinal bacterial overgrowth. You may have also been told your gut tests are normal, or been handed a diagnosis of IBS without any real explanation of what is driving it.

SIBO is one of the most underdiagnosed digestive conditions I see in my practice. It is also one of the most fixable when properly identified. This post is for anyone who suspects their gut might be the source of symptoms that go far beyond just digestion.

Up to 60%  of IBS cases.

Research suggests that small intestinal bacterial overgrowth may be present in a large share of people diagnosed with irritable bowel syndrome, meaning many IBS diagnoses may actually have SIBO as an underlying driver.

What Is SIBO and Why Does It Happen?

The small intestine is designed to be relatively low in bacteria. Most of the gut's microbial population lives in the large intestine. Small intestinal bacterial overgrowth occurs when bacteria, often from the colon, migrate upward and colonize the small intestine in numbers that disrupt normal digestion and absorption. The National Institute of Diabetes and Digestive and Kidney Diseases notes that SIBO can interfere with nutrient absorption and damage the lining of the small intestine over time.

Several factors can disrupt the mechanisms that normally prevent bacterial overgrowth. Reduced stomach acid, whether from aging, stress, or proton pump inhibitor use, allows more bacteria to survive in the upper GI tract. Impaired motility means the wave-like contractions that sweep the gut between meals are not clearing bacteria effectively. Structural issues from surgery or adhesions, immune dysfunction, and conditions like hypothyroidism that slow gut motility are all contributing factors. Chronic stress plays a role as well, which is why SIBO is so commonly found alongside hormonal and autoimmune conditions in the women I work with.

SIBO Symptoms to Watch For

What makes SIBO tricky is that its symptoms overlap heavily with other conditions, including IBS, leaky gut, food intolerances, and even hormonal imbalances. The key distinguishing feature is that SIBO symptoms are often worse after eating, particularly after meals that are high in fermentable carbohydrates.

The most common symptoms I see in patients with confirmed SIBO include chronic bloating that is often worse in the afternoon and evening, excessive gas and belching, abdominal cramping and pain, irregular bowel habits including constipation, diarrhea, or both alternating, nausea particularly after eating, and a feeling of fullness that comes on very quickly during meals.

Beyond the gut, SIBO can produce a surprising range of systemic symptoms. Fatigue and brain fog are extremely common and are thought to result from the inflammation and malabsorption SIBO causes. Joint pain, skin issues including rosacea and eczema, mood disturbances including anxiety and depression, and nutritional deficiencies, particularly B12, iron, and fat-soluble vitamins, are all documented in SIBO patients. This is why SIBO is often missed: patients report symptoms that seem unrelated to their gut and end up with multiple specialist referrals before anyone connects the dots.

Some of the most striking cases I see are patients who have spent years chasing fatigue, brain fog, and joint pain through multiple specialists, with no one thinking to look at the gut. When SIBO turns out to be the missing piece, addressing it can change the entire picture.

-- Dr. Juline Savaya, NMD

How Is SIBO Diagnosed?

The gold standard for SIBO diagnosis is a lactulose or glucose breath test, which measures the hydrogen and methane gases produced by bacteria as they ferment a sugar substrate. Elevated gas levels in the early part of the test indicate bacterial overgrowth in the small intestine. Some practitioners also look at methane levels separately, as methane-dominant SIBO, now more precisely called IMO or intestinal methanogen overgrowth, tends to present more with constipation and responds differently to treatment.

In my practice, I also run comprehensive stool analysis to assess the large intestinal microbiome, markers of gut inflammation, digestive enzyme function, and intestinal permeability. I look at the full picture because SIBO rarely exists in isolation. It is almost always part of a larger pattern of gut dysfunction that needs to be addressed alongside the bacterial overgrowth itself.

How Naturopathic Medicine Addresses SIBO

Conventional treatment for SIBO typically involves a course of rifaximin, an antibiotic that is minimally absorbed into the bloodstream and works primarily within the digestive tract to reduce bacterial overgrowth. While this approach can be effective, SIBO is often more complex than simply having too much bacteria in the small intestine. Without identifying and addressing the underlying drivers, recurrence is common.

This is where naturopathic medicine adds a layer that most conventional approaches skip. In addition to clearing the bacterial overgrowth, I focus on identifying and addressing the root cause, whether that is low stomach acid, impaired motility, thyroid dysfunction, stress-related changes to gut function, or another driver. Without fixing the root cause, SIBO comes back.

Herbal antimicrobial protocols using botanicals like berberine, oregano oil, and allicin have shown comparable efficacy to rifaximin in published research and are often preferred for patients who want to avoid antibiotics or who have had repeated antibiotic courses. Dietary strategies play an important supporting role, and a low-fermentable carbohydrate approach can significantly reduce symptom burden during treatment. Prokinetics, which are agents that support gut motility between meals, are essential for preventing recurrence, and there are effective naturopathic options alongside pharmaceutical ones.

Gut lining repair is typically the final phase of treatment: replacing what SIBO has depleted, restoring the mucosal barrier, and reseeding the microbiome appropriately once the overgrowth has been cleared.

Why SIBO Is So Common in Women with Hormonal Issues

This is something I see constantly in my practice: a patient comes in with PCOS, endometriosis, or thyroid disease, and when we dig into her symptoms, she also has classic signs of SIBO. This overlap is not a coincidence.

Hormones play an important role in digestive function. Estrogen can influence both gut function and the composition of the gut microbiome, while thyroid hormones help regulate gut motility. Hypothyroidism, even when mild, can slow intestinal transit and create conditions where bacteria are more likely to overgrow. Cortisol released during chronic stress can reduce stomach acid production, impair the gut's protective barriers, and disrupt the migrating motor complex (MMC), the gut's natural cleansing wave that helps prevent bacterial overgrowth.

The gut also influences estrogen through what is called the estrobolome, the collection of gut bacteria that help metabolize and regulate circulating estrogen. When the gut microbiome is disrupted, estrogen metabolism can be affected in ways that contribute to hormonal imbalances, which may show up as heavy periods, PMS, or symptoms associated with conditions like endometriosis.

RELATED SERVICE

Digestive Health

How Dr. Savaya approaches IBS, SIBO, and gut health using a root-cause framework, in Arizona and Michigan.

When to Seek an Evaluation for SIBO

Consider a comprehensive gut evaluation if any of the following apply to you:

• You have been diagnosed with IBS but treatment has not resolved your symptoms

• You experience significant bloating, gas, or abdominal distension after meals

• Your bowel habits are unpredictable or have changed significantly

• You have unexplained fatigue, brain fog, or mood changes alongside gut symptoms

• You have a history of frequent antibiotic use, a gut infection, or abdominal surgery

• You have been told you have food intolerances to many different foods

• You have a condition that slows gut motility, including hypothyroidism or a connective tissue disorder

• Your gut symptoms seem to worsen with stress

You do not have to keep living with symptoms that your current care has not been able to explain. SIBO is testable and treatable, and addressing it can have a meaningful ripple effect on symptoms far beyond the gut.

WRITTEN BY

Dr. Juline Savaya, NMD

Licensed Naturopathic Physician (Arizona)  |  Naturopathic Health Consultant (Michigan)

Dr. Savaya specializes in women's health, hormones, fertility, and gut health. She sees patients via telehealth across Arizona and in-person and virtually in Michigan.

Learn more about Dr. Savaya.

References

1. National Institute of Diabetes and Digestive and Kidney Diseases (2023). Small Intestinal Bacterial Overgrowth. niddk.nih.gov

2. Pimentel M. et al. (2020). ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth. American Journal of Gastroenterology.

3. Baker J.M. et al. (2017). Estrogen-gut microbiome axis: physiological and clinical implications. Maturitas. pubmed.ncbi.nlm.nih.gov/28778332

4. Chedid V. et al. (2014). Herbal therapy is equivalent to rifaximin for the treatment of SIBO. Global Advances in Health and Medicine.