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Genova SIBO Testing 101

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Genova SIBO Testing 101

Small intestinal bacterial overgrowth (SIBO) is a commonly overlooked digestive condition characterized by bacterial overgrowth in the upper digestive tract. SIBO can develop due to low stomach acidity, slowed small intestinal motility, anatomical variations, and gastrointestinal infections that predispose to an overgrowth of bacteria in the small intestine. SIBO typically causes uncomfortable digestive symptoms like bloating, abdominal pain, and changes in bowel habits. However, with increased recognition, newer research suggests that SIBO is associated with signs and conditions outside the gastrointestinal system. SIBO breath testing is a convenient, at-home breath test for diagnosing SIBO. This article will discuss Genova Diagnostics' 2- and 3-Hour SIBO Lactulose Breath Tests available for order through the Rupa Health portal.


What is the SIBO 2-Hour Test from Genova Diagnostics?

The SIBO 2-Hour Breath Test is a non-invasive diagnostic method for diagnosing SIBO. After the patient drinks a lactulose-containing solution, breath samples are collected for two hours at spaced intervals. A total of six breath samples are collected at home during the test.

As the lactulose travels through the intestines, bacteria (hydrogen-producers) and archaea (methane-producers) ferment the sugar, creating hydrogen (H2) and methane (CH4) gases that are expired through the lungs. Understanding what we know about intestinal transit time, the timing of the breath collections reflects the location of bacteria in the intestines. A 2-hour breath test measures gases derived from bacteria and archaea colonizing the small intestine.

What is the SIBO 3-Hour Test from Genova Diagnostics?

Genova's SIBO 3-Hour Breath Test is almost identical to the 2-Hour version, except for a longer testing period. Instead of collecting a total of six breath samples, the patient performing the test collects breath samples at spaced time intervals for three hours. A total of eight breath samples are collected at home during the test.

Why Choose a 2-Hour vs. 3-Hour Test?

The small intestine has three parts: the duodenum, jejunum, and ileum. In a patient with regular intestinal transit, the first 90-120 minutes measures gases derived in the small intestine; the third hour of the 3-Hour test measures gases derived in the large intestine.

The 2-Hour test can be problematic and less accurate than the 3-Hour test for a couple of reasons. First, people who have slowed intestinal motility may need an extended test to assess for bacterial overgrowth in the small intestine more accurately. Additionally, we now understand that CH4 overproduction (termed "intestinal methanogen overgrowth") in the small or large intestines can contribute to negative digestive symptoms. So, while a 2-Hour test may be sufficient in diagnosing H2-SIBO, a 3-Hour test is required to measure CH4 gas levels sufficiently.

Which Patients is Genova's SIBO Test Best Used For?

Genova's SIBO Breath Test should be ordered for anyone you suspect has SIBO. SIBO can cause many symptoms, not always specific to the gut. Common symptoms that may warrant evaluation for SIBO include:

  • Gastrointestinal: bloating, gas, diarrhea, constipation, abdominal pain, heartburn, nausea, food intolerances
  • Psychological: anxiety, depression, brain fog
  • Constitutional: fatigue, weight loss
  • Musculoskeletal: muscle and joint pain

SIBO has also been found to be associated with many other medical conditions. The diagnosis and treatment of SIBO can help get to the root cause of the following diseases:


Irritable Bowel Syndrome (IBS): Research has indicated that up to 78% of patients with IBS have co-existing SIBO. Methane overproduction has been associated with slowed intestinal motility and constipation, whereas hydrogen predominance is associated with diarrheal presentations.


Inflammatory Bowel Disease (IBD): A large meta-analysis including 11 studies and over 1000 patients with IBD determined that over 20% of patients with IBD also had SIBO and that patients with an IBD diagnosis had a ninefold increased risk of developing SIBO than healthy individuals.  

Celiac Diesease

Celiac Disease: Another systematic review, including 11 studies, revealed a 20% prevalence rate of SIBO in patients with celiac disease. SIBO needs to be ruled out in patients with celiac disease who do not experience an improvement in symptoms with a gluten-free diet.


Diabetes: 29% of patients with diabetes mellitus have SIBO, and the risk of SIBO in these patients is 2.91 times higher than in patients without diabetes.


Fibromyalgia: Patients with fibromyalgia have a high rate of SIBO occurrence. Additionally, the degree of hydrogen abnormality measured on the breath test correlates with somatic pain experienced by people with fibromyalgia.


Rosacea: Not only does research show that rosacea patients have a significantly higher SIBO prevalence than those who do not, but SIBO eradication results in almost a complete regression of rosacea lesions.

Parkinson's Disease

Parkinson's Disease: A 2021 systematic review concluded that almost half of patients with Parkinson's test positive for SIBO. This may not be surprising, knowing that chronic constipation is common among people who have Parkinson's, and it is suggested that constipation may be an early symptom of the disease before classic neurological symptoms appear.


Obesity: A systematic review including five studies and over 500 patients assessing the risk of SIBO in the obese population concluded that obesity predisposes SIBO development.

Restless Leg Syndrome

Restless Leg Syndrome (RLS): A high prevalence of bacterial overgrowth has been observed in people with neuromuscular disorders, such as RLS. Additionally, RLS occurs much more frequently in patients with coexisting IBS.

Interstitial Cystitis

Interstitial Cystitis (IC): IBS often coexists with and increases the risk of developing IC. A high rate of positive SIBO breath tests is associated with patients with both gastrointestinal and urinary symptoms.


Hypothyroidism: Slowed intestinal motility caused by low thyroid hormones can increase the risk of bacterial overgrowth and digestive symptoms.

Malabsoprtion Syndrome

Malabsorption Syndrome: The presence of SIBO disrupts the healthy digestive processes of the gastrointestinal tract, commonly causing nutritional deficiencies of vitamin B12, iron, and fat-soluble vitamins.

How to Use Genova's SIBO Test in Clinic

The SIBO 2- or 3-Hour Breath Test can be used clinically to diagnose SIBO, differentiate between SIBO subtypes (H2-SIBO vs. CH4-intestinal methanogen overgrowth vs. mixed H2/CH4), and determine SIBO severity. The North American Consensus considers a positive breath test if hydrogen levels rise at least 20 ppm by 90 minutes and/or if peak methane levels reach at least 10 ppm at any point during the test. If neither single gas level is positive using the Consensus guidelines, a positive test can be determined with a combined H2 and CH4 level of at least 15 ppm after baseline.

Common but preventable mistakes leading to inaccurate test results involve incorrect patient preparation and collection procedure. Ensure the patient is well-informed on both before sending them home with the test kit.

Patients must follow a day-long modified preparation diet the day before collecting breath samples. Foods allowed to be eaten 24 hours before test collection include plain chicken, fish, turkey, white bread, steamed white rice, eggs, clear chicken and beef broth, and water. Patients should not eat or drink anything other than water for 12 hours before and during the test.

Additionally, it is recommended that this test not be collected within four weeks of undergoing colonoscopy or barium enema. Natural and prescription antibiotics can interfere with test results if taken 2-4 weeks before patient collection. It is not recommended to take them during this timeframe before an initial/baseline SIBO breath test, but it is ok to take them leading up to a SIBO retest to monitor treatment efficacy. Medications like laxatives, stool softeners, and stool-bulking agents can also interfere with the test results.

This SIBO breath test should not be ordered for anyone allergic to lactulose. Lactose intolerant patients generally can tolerate the lactulose solution but should be advised that the test may aggravate digestive symptoms. Lactulose can also cause blood sugar elevations, so caution should be taken when ordering the test for patients with diabetes.

SIBO eradication requires natural and/or prescriptive antibiotic therapy. An elemental diet is a treatment alternative to antimicrobial therapy. Dietary modifications, such as the low FODMAP diet, are also often recommended to palliate digestive symptoms during treatment.


SIBO breath testing can be an exceptionally helpful diagnostic tool for patients struggling with digestive, neuromuscular, endocrine, and skin conditions. Genova Diagnostics offers a lactulose breath test for SIBO diagnosis, which can be performed by the patient at home in either two or three hours. Test results confirm a SIBO diagnosis and differentiate between hydrogen and methane subtypes, helping to guide treatment recommendations.

The information provided is not intended to be a substitute for professional medical advice. Always consult with your doctor or other qualified healthcare provider before taking any dietary supplement or making any changes to your diet or exercise routine.
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