Can a Doctor Test for SIBO?

When I first started my practice at Dignity Integrative, one of the most frequent questions patients asked me was whether there was actually a reliable test for SIBO. Many had been bouncing from doctor to doctor, dealing with bloating, gas, abdominal pain, and unpredictable bowel movements for months or even years. Some had been told they had irritable bowel syndrome and sent home with symptom management strategies that didn't really help. Others had been through multiple rounds of testing that came back "normal," leaving them frustrated and wondering if their symptoms were all in their head.

The short answer is yes—doctors can absolutely test for SIBO. But like many things in medicine, the longer answer is more nuanced and reveals why so many patients struggle to get an accurate diagnosis.

The Challenge of SIBO Testing

Small Intestinal Bacterial Overgrowth is exactly what it sounds like: too many bacteria living in your small intestine, where only a small, select population of microorganisms should normally reside. Unlike your large intestine, which is supposed to be teeming with trillions of microbes, your small intestine should be relatively sparsely populated.

The challenge is that SIBO symptoms—bloating, gas, abdominal pain, diarrhea, constipation, food sensitivities, and fatigue—overlap significantly with many other digestive conditions. In fact, research suggests that somewhere between one quarter and one half of patients diagnosed with irritable bowel syndrome actually have underlying SIBO. This overlap means that getting the right test is crucial for getting the right treatment.

The Breath Test: Current Standard of Care

The most common way doctors test for SIBO today is through breath testing. This non-invasive test works on a simple principle: bacteria in your small intestine ferment carbohydrates and release gases as byproducts. While 80% of these gases remain in your intestines, the other 20% gets absorbed into your bloodstream, travels to your lungs, and comes out when you exhale.

The test itself is straightforward. After following a specific preparation diet and fasting overnight, you drink a sugary solution containing either glucose or lactulose. Then you collect breath samples by breathing into special tubes at timed intervals—usually every 15 to 20 minutes for up to three hours. These samples are analyzed in a laboratory to measure hydrogen and methane levels.

There are actually three types of SIBO that can be detected through breath testing. Hydrogen SIBO is the most common, caused by bacteria that produce hydrogen gas. Methane SIBO—now more accurately called Intestinal Methanogen Overgrowth or IMO—involves methane-producing organisms called archaea. These ancient microorganisms aren't technically bacteria, but they can cause similar symptoms, particularly constipation. There's also a third type involving hydrogen sulfide production, which was undetectable until recently with the introduction of specialized testing like the Trio-Smart breath test.

The Accuracy Question

Here's where things get complicated. While breath testing is widely available and non-invasive, it's not perfect. The accuracy of these tests ranges from about 42% to 83%, depending on the specific test and how it's performed. This means there can be false positives—where the test suggests you have SIBO when you don't—and false negatives, where you actually have SIBO but the test doesn't detect it.

Several factors can affect test accuracy. People who digest food faster than average are more likely to get false positive results. Those with gastroparesis, where the stomach empties slowly, might get false negative results. The type of sugar used in the test also matters: glucose tests tend to be more specific but potentially less sensitive, while lactulose tests might catch more cases but could produce more false positives.

The preparation for the test is crucial. Patients need to avoid certain foods for 24 hours before testing, stop taking antibiotics at least four weeks prior, and discontinue certain medications like prokinetic drugs and laxatives about a week beforehand, though this should always be done under medical supervision.

The "Gold Standard" That Isn't Really Golden

Traditionally, the most accurate way to diagnose SIBO has been through small intestine aspiration—a procedure where a doctor passes a flexible tube down your throat and into your small intestine to collect a sample of intestinal fluid. This fluid is then tested in a laboratory for bacterial growth.

Recent advances have brought this test back into focus. UC Davis Health made headlines in 2024 as the first hospital in their region to perform what they call the "gold standard" small intestine aspirate procedure. Dr. Hisham Hussan, who performs these procedures, notes that traditional breath tests are only about 60% accurate, meaning many patients who undergo breath testing will be misdiagnosed.

The aspirate procedure offers several advantages beyond just better accuracy. It can identify the specific bacteria causing the overgrowth and test their sensitivity to different antibiotics, allowing for more targeted treatment. It can also diagnose Small Intestine Fungal Overgrowth, another condition that breath testing can't detect.

However, this more accurate test comes with significant limitations. It's expensive, invasive, and not widely available. The procedure requires sedation, carries small risks like any endoscopic procedure, and requires specialized expertise that most medical centers don't have. There's also a risk of contamination from bacteria in the mouth, which can lead to incorrect diagnoses.

Even calling it a "gold standard" is somewhat misleading. There's actually no true gold standard test for SIBO diagnosis because experts still don't fully agree on the exact definition of the condition or the bacterial thresholds that constitute overgrowth.

At-Home SIBO Testing: Convenience with Considerations

One significant development in SIBO testing has been the availability of at-home breath test kits. These kits, which can cost anywhere from $100 to $300, allow patients to collect breath samples in the comfort of their own homes and mail them to laboratories for analysis.

The convenience factor is obvious—no need to take time off work or travel to a medical facility. For people with mild to moderate symptoms who haven't been previously diagnosed, these tests can provide valuable initial information. Some are available over-the-counter, while others require a prescription and may be covered by insurance.

However, at-home testing isn't appropriate for everyone. People with a history of gastrointestinal disorders, those who have been previously treated for SIBO, or patients with complex medical conditions should generally test under medical supervision. The interpretation of results is also crucial—what looks like a positive test might not actually indicate SIBO, and what appears negative might not rule it out, especially without proper clinical context.

The Integrative Medicine Difference

As an integrative medicine physician, I've learned that SIBO testing is just one piece of a much larger puzzle. While getting an accurate diagnosis is important, the more crucial question is often why someone developed SIBO in the first place.

Traditional gastroenterology typically focuses on confirming the diagnosis and prescribing antibiotics like rifaximin. This approach can be effective, but it often misses the underlying factors that allowed bacterial overgrowth to develop. Without addressing these root causes, many patients find their symptoms returning even after successful treatment.

In my practice, I use breath testing as part of a more comprehensive evaluation. Beyond the standard breath test, I often recommend comprehensive stool analysis to get a complete picture of gut health, and depending on the individual case, additional testing to rule out other conditions or identify underlying causes. This might include evaluating thyroid function, checking for heavy metal exposure, assessing digestive enzyme adequacy, or examining gut motility. All of these tests come with pros and cons requiring interpretation in the context of the individual patient.

The key insight is that SIBO is rarely a random occurrence. It's usually the result of underlying dysfunction—perhaps slowed gut motility due to thyroid issues, structural problems from previous surgeries, digestive deficits from long-term stress, or medication effects. Identifying and addressing these underlying issues is crucial for long-term success.

What This Means for Patients

If you're experiencing persistent digestive symptoms that suggest SIBO, the good news is that testing is definitely available. The breath test, despite its limitations, remains the most practical and widely accessible option. It's non-invasive, relatively inexpensive, and can provide valuable information when interpreted by an experienced practitioner.

The key is working with a healthcare provider who understands both the capabilities and limitations of SIBO testing. They should be able to interpret results in the context of your overall health picture and help you understand what the findings mean for your specific situation.

It's also important to understand that SIBO testing, like many medical tests, is a tool for gathering information—not necessarily a definitive answer. A positive test doesn't automatically mean you need aggressive antibiotic treatment, and a negative test doesn't necessarily rule out SIBO if your symptoms strongly suggest it.

For patients dealing with recurrent SIBO, the testing becomes even more complex. The high recurrence rates we see with SIBO—between 40 and 60% within 9 to 12 months after treatment—suggest that simply testing for and treating the bacterial overgrowth isn't enough. This is where working with a practitioner trained in functional or integrative medicine can be invaluable, as they're more likely to investigate and address the underlying factors that allowed SIBO to develop.

Looking Forward

The field of SIBO testing continues to evolve. We're seeing improvements in breath testing technology, like the ability to measure hydrogen sulfide in addition to hydrogen and methane. There's also growing research into the gut microbiome that may eventually lead to better diagnostic tools.

What hasn't changed is the importance of a thoughtful, comprehensive approach to diagnosis and treatment. SIBO testing is most useful when it's part of a broader evaluation that considers the whole person, not just the bacterial overgrowth.

For patients struggling with digestive symptoms, the message is clear: yes, doctors can test for SIBO, and testing can provide valuable information. But the real key to long-term success lies in finding a practitioner who can interpret those test results in the context of your individual health needs and help address not just the bacterial overgrowth, but the underlying factors that allowed it to develop in the first place.

If you're struggling with persistent digestive symptoms and wondering whether SIBO testing might be right for you, consider scheduling a free, 15-minute consultation with Dignity Integrative. We can help you understand your testing options and develop a comprehensive approach to addressing your digestive health.