Endometriosis and SIBO: The Overlap Most Doctors Miss

You’re lying on the couch after dinner, watching your belly swell like you’re six months pregnant — even though all you ate was a salad. You’ve told your doctor about the bloating dozens of times, but the conversation always dead-ends at “it’s just your endo” or “try a low-FODMAP diet.”

How Common Is SIBO in People With Endometriosis?

Observational studies suggest that a large majority of people with endometriosis report gastrointestinal symptoms — including bloating, constipation, diarrhea, and nausea — at rates far higher than the general population. One Australian cross-sectional study found that 90% of women with confirmed endometriosis had one or more GI complaints. In one 2025 case-control study of women who underwent breath testing at a French GI laboratory (n=296 matched pairs drawn from a cohort of 1,027), SIBO or IMO was detected in 91.9% of endometriosis patients versus 83.1% of controls — a statistically significant difference (p=0.0223). Importantly, the high rate in both groups reflects the fact that this cohort was enriched for GI-symptomatic individuals who sought breath testing, rather than a general population sample.

These two conditions don’t just happen to coexist — they actively fuel each other. Endometriosis creates the conditions for SIBO to develop, and SIBO amplifies the inflammation and bloating that make endometriosis symptoms worse. This bidirectional relationship is what practitioners call the gut-pelvic axis: a framework connecting pelvic inflammation, gut bacteria, intestinal motility, and hormonal cross-talk into one interconnected system. If you want a deeper look at how this shows up in the belly, see endo belly: what causes it and how to calm it.

What Is SIBO?

SIBO affects an estimated 2.5–22% of the general population, depending on the testing method used, and that number climbs sharply in people with conditions that slow gut motility. In simple terms, SIBO means bacteria that normally live in your large intestine have migrated into your small intestine, where they don’t belong.

Your small intestine is designed to be relatively low in bacteria. It has built-in cleaning mechanisms — waves of muscular contractions called the migrating motor complex (MMC) that sweep bacteria downward roughly every 90 minutes during fasting. When those cleaning waves are disrupted, bacteria accumulate, ferment the food you eat, and produce excess gas. That gas is what causes the intense bloating, abdominal distension, and discomfort that can feel indistinguishable from endo belly.

How does the estrobolome connect endometriosis to gut symptoms?

The estrobolome is the collection of gut bacteria that produce enzymes — particularly beta-glucuronidase and sulfatases — capable of metabolizing estrogen. These enzymes deconjugate estrogen that the liver has already processed for excretion, allowing it to be reabsorbed into circulation rather than eliminated. When the bacteria producing these enzymes are overrepresented, your body keeps recycling estrogen it is trying to clear.

The estrobolome is altered in endometriosis. A 2023 mouse model study found that endometriosis is associated with estrobolome dysregulation and altered immune metabolism. The exact direction is still being worked out: it is unclear whether dysbiosis drives endometriosis, whether endometriosis drives dysbiosis, or whether both are true at once. Endometriotic lesions themselves also produce estrogen locally through increased aromatase expression, which is one reason hormonal suppression alone does not always provide complete symptom relief — the gut and the lesions are both contributing to the estrogenic environment.

Why Does Endometriosis Increase SIBO Risk?

Gut motility changes

In the same 2025 case-control study, 85.8% of endometriosis patients had altered intestinal transit, compared with 71% of controls. Endometriosis-related inflammation may impair the migrating motor complex — those cleaning waves that keep bacteria from accumulating. When motility slows, bacteria have time to settle and multiply in the small intestine. Progesterone, which rises in the second half of the menstrual cycle, also naturally slows gut motility, which may help explain why endo belly often worsens in the luteal phase.

Inflammation and intestinal permeability

Endometriosis is a chronic inflammatory disease that elevates cytokines and immune mediators throughout the body — not just in the pelvis. This systemic inflammation can increase intestinal permeability (sometimes called “leaky gut”), allowing bacterial byproducts like lipopolysaccharide (LPS) to cross the gut lining and trigger further immune activation. A pilot case-control study found significantly higher plasma LPS levels in women with endometriosis than in controls, supporting the idea that the intestinal barrier is more permeable in endo. Once bacterial products like LPS enter the bloodstream, they trigger systemic inflammation and immune activation, creating a feedback loop: inflammation damages the gut barrier, more bacterial products cross through, and more inflammation follows. Pelvic inflammation disrupts the gut, and gut disruption worsens pelvic inflammation.

Bacterial translocation from the gut

A 2025 paper in Gut demonstrated that gut bacteria can translocate from the intestine into the peritoneal cavity in endometriosis. Gut-derived bacteria, particularly Pseudomonas, cross the intestinal barrier and reach endometriotic lesions, where they trigger immune responses (including NETosis) that promote disease progression. In the same study, fecal microbiota transplantation from endometriosis patients to mice disrupted the intestinal barrier and promoted this translocation. This is not just a correlation between gut health and endo — bacteria appear to be physically crossing from the gut into the pelvis and making the disease worse.

Surgery and adhesions

Pelvic and abdominal surgeries — including laparoscopic excision for endometriosis — can create adhesions (bands of scar tissue) that kink or partially obstruct the small intestine. The ACG Clinical Guideline on SIBO identifies post-surgical adhesions and anatomical changes as established risk factors for bacterial overgrowth. Research consistently documents meaningfully higher SIBO prevalence after abdominal surgery compared with non-surgical controls. This doesn’t mean you should avoid necessary surgery — it means post-surgical gut health deserves attention.

Hormonal factors

A key piece of the puzzle is the estrobolome — a collection of gut bacteria that help metabolize estrogen. When gut bacteria are out of balance, the estrobolome can recirculate a significant proportion of estrogen back into circulation instead of clearing it. Because endometriosis is estrogen-dependent, this excess estrogen may contribute to lesion growth, which in turn is linked to more inflammation and more gut disruption. Recent reviews of the endometriosis microbiome literature have documented consistent differences in gut microbiota diversity between women with and without endometriosis, though the estrobolome’s exact role in endometriosis is still being studied.

GI doctors tend to treat SIBO as a standalone gut problem, and gynecologists tend to treat endo belly as a standalone pelvic problem. But the gut-pelvic axis means these are the same problem viewed from two different angles. Motility, microbiome, hormones, and inflammation are all talking to each other — and effective treatment needs to address the whole conversation.

What Are the Symptoms That Suggest SIBO?

In the 2025 case-control study, 67.8% of endometriosis patients with SIBO reported constipation, compared with 44.7% of those without endometriosis, and dizziness was also significantly more common (44.8% vs. 28.7%). Symptoms that may point to SIBO on top of your endometriosis include:

• Bloating that worsens within 30–90 minutes of eating
• Excessive gas and belching
• Alternating constipation and diarrhea
• Bloating that doesn’t follow your menstrual cycle pattern (endo belly typically worsens premenstrually, while SIBO bloating is more constant)
• Nausea or acid reflux
• Fatigue and brain fog
• Symptoms that don’t fully improve with hormonal endo treatments

Bloating is often called the hallmark SIBO symptom, but a 2020 systematic review and meta-analysis found that diarrhea — not bloating — actually has the strongest association with SIBO. If you have unexplained loose stools alongside your endo symptoms, that is an important clue worth flagging to your provider.

How Is SIBO Tested?

The gold standard for SIBO diagnosis is a small bowel aspirate and culture, but this requires an endoscopy and is rarely used in practice. The most common clinical test is a breath test — either a lactulose or glucose breath test — which measures hydrogen and methane gases produced by bacteria after you drink a sugar solution.

You fast overnight, drink the solution, and breathe into collection tubes every 15–20 minutes for about 90 minutes. A rise in hydrogen of ≥20 parts per million (ppm) above baseline within 90 minutes suggests SIBO. A methane level ≥10 ppm at any point suggests intestinal methanogen overgrowth (IMO), which is more closely linked to constipation. In the 2025 endometriosis study, methane overgrowth accounted for roughly 63% of positive results in endo patients — a pattern that aligns with the constipation-predominant symptoms many people with endometriosis report.

What Are the Treatment Approaches for SIBO?

A single 7- to 10-day course of antibiotics improves symptoms in 46–90% of SIBO patients and normalizes breath tests in 20–75%. The most studied antibiotic is rifaximin, a gut-targeted antibiotic with a roughly 70% eradication rate in a meta-analysis of 32 clinical trials. ACG guidelines recommend rifaximin 550 mg three times daily for 14 days as first-line therapy.

For methane-dominant overgrowth (IMO) — which is common in endometriosis — a combination of rifaximin plus neomycin may be more effective, because methane-producing archaea don’t respond as well to rifaximin alone. Beyond antibiotics, treatment should address the underlying reasons SIBO developed:

• Prokinetic agents to restore the migrating motor complex and prevent recurrence
• Dietary modifications such as a short-term low-FODMAP or elemental diet to reduce fermentable substrates
• Addressing hormonal drivers through coordinated endometriosis management
• Probiotics, which have shown promise in reducing endometriosis-associated symptoms in early research, though clinical trial data remain limited

Recurrence is common — up to 44% within 9 months in one follow-up study — which is why treating the root causes (motility, inflammation, hormonal imbalance) matters as much as the antibiotic itself. For overlap with IBS symptoms, see endometriosis and IBS: the gut-pelvic connection.

Why Can Treating SIBO Ease Endo Belly?

When SIBO is contributing to your bloating, treating it can provide significant relief — but the key word is contributing. Endo belly has multiple drivers, including pelvic inflammation, fluid retention, and visceral hypersensitivity (a lower pain threshold in the intestinal wall). SIBO adds bacterial gas production on top of all of that.

Treating SIBO won’t “cure” endo belly — but it can remove one major layer of the problem. Think of it as turning down one of several volume knobs. When you reduce the bacterial gas production, the remaining symptoms become more manageable and more responsive to endo-specific treatments. For day-of flare-ups, see how to stop an endometriosis flare fast.

How do you tell if your IBS is actually endometriosis?

Endometriosis patients are roughly 3 times more likely to meet criteria for IBS than women without endometriosis, a finding confirmed across multiple meta-analyses. Many people spend years on FODMAP protocols and probiotics for an IBS label that never quite explains everything. The symptom overlap is substantial — bloating, abdominal pain, altered bowel habits, cramping — but there are patterns that suggest endometriosis is the upstream driver:

Cyclical worsening. If your GI symptoms consistently worsen during menstruation or specific phases of your cycle, that is a pattern IBS alone does not explain. Rome criteria for diagnosing IBS do not account for cyclical patterns or gynecological symptoms — which is exactly how endometriosis gets missed.

Symptom clustering. Endometriosis rarely shows up as gut symptoms in isolation. Painful periods, pain with intercourse, chronic pelvic pain, and fatigue alongside GI complaints point to a systemic condition, not a functional bowel disorder.

Treatment resistance. If you have done the low-FODMAP diet, tried probiotics, cut gluten, and still cycle through the same symptoms monthly, the IBS playbook is not addressing what is actually happening. A 2025 RCT did show that about 60% of women with endometriosis respond to a low-FODMAP diet, but dietary modification does not address the inflammatory environment driving the dysbiosis.

Direct bowel involvement. Endometriotic lesions can infiltrate the bowel wall directly. These may not be visible on standard colonoscopy if they sit in the submucosa or serosa. A negative colonoscopy does not rule out endometriosis affecting the bowel. For more on this, see why bowel endometriosis causes digestive problems.

When to Seek Care

Contact a provider if you experience:

• Abdominal pain rated 7/10 or higher that doesn’t respond to your usual management
• Fever above 100.4°F (38°C) with abdominal symptoms
• Unintentional weight loss of more than 5% of body weight over 6–12 months
• Persistent diarrhea lasting more than 4 weeks
• Signs of nutritional deficiency (unusual fatigue, numbness or tingling, easy bruising)
• Bloating so severe it interferes with eating, sleeping, or daily activities

These symptoms may indicate SIBO, but they can also signal other conditions that need evaluation.

How Do You Find a Provider Who Treats Both?

Most endometriosis patients wait an average of 7–10 years for a diagnosis. Adding SIBO to the picture requires a provider who can see both the pelvic and the gut sides of the equation. Based on current evidence, endometriosis does not directly “cause” SIBO — but it is associated with a constellation of risk factors (impaired motility, chronic inflammation, surgical adhesions, and hormonal disruption) that make SIBO significantly more likely to develop. Treating the endo without addressing the gut, or treating the gut without addressing the endo, often leaves patients stuck in a cycle of partial improvement and frustrating recurrence. If gut symptoms are showing up with nervous-system flare-ups too, see endometriosis and nervous system dysregulation.

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