SIBO Breath Test
Detect small intestinal bacterial overgrowth with a clinician-grade 3-hour glucose breath test — measuring hydrogen and methane gas levels at timed intervals to pinpoint exactly where overgrowth is occurring.
Do any of these sound familiar?
Select every symptom you recognise. If you match 2 or more, the SIBO Breath Test can help identify whether small intestinal bacterial overgrowth is the underlying cause.
The hallmark symptom of SIBO. Bacteria that should not be in the small intestine ferment carbohydrates prematurely, producing hydrogen and methane gas before food reaches the large bowel. This causes visible abdominal distension, pressure, and discomfort — often worsening throughout the day and after meals.
When bacteria colonise the small intestine, they ferment sugars and starches that would normally be absorbed. The result is excessive hydrogen, methane, or hydrogen sulphide gas production far higher than normal. This breath test measures these gases directly to determine if bacterial overgrowth is the source.
Methane-dominant SIBO specifically slows intestinal transit. The methane gas produced by archaea (primarily Methanobrevibacter smithii) directly inhibits smooth muscle contractions in the gut wall, leading to chronic constipation that does not respond to fibre supplementation or standard laxatives. This test detects elevated methane levels.
Hydrogen-dominant SIBO typically presents with loose stools, urgency, and increased bowel frequency. Excess bacteria in the small intestine damage the mucosal lining, impair nutrient absorption, and draw water into the bowel through osmotic mechanisms — producing watery diarrhoea that can mimic IBS-D.
Many SIBO patients alternate between the two. This mixed pattern often reflects a combination of hydrogen and methane-producing organisms competing in the small intestine. Standard IBS treatment rarely resolves it because the underlying bacterial overgrowth is not being addressed.
SIBO increases intra-abdominal pressure through excessive gas production, which can force stomach contents upward through the lower oesophageal sphincter. If your reflux has not responded to PPIs or diet changes, bacterial overgrowth in the small intestine may be the mechanical driver your gastroenterologist has not tested for.
If you have become increasingly reactive to foods you used to tolerate — particularly FODMAPs, garlic, onion, bread, or legumes — SIBO may be the cause. Overgrown bacteria ferment these foods aggressively in the small intestine, producing symptoms that look like food intolerance but are actually a bacterial problem.
Post-meal nausea — especially within 30–90 minutes of eating — can indicate SIBO. Bacterial fermentation begins in the small intestine almost immediately after food arrives, producing gas and distension that triggers nausea, early satiety, and upper abdominal discomfort before food even reaches the colon.
Chronic cramping and abdominal pain — particularly in the central or upper abdomen — can result from gas distension and inflammation caused by bacterial overgrowth in the small intestine. The pain often fluctuates with meals and is poorly explained by standard imaging or endoscopy.
Up to 78% of IBS patients test positive for SIBO when properly tested. If you have been diagnosed with Irritable Bowel Syndrome but treatments have not worked, the underlying cause may be bacterial overgrowth that standard IBS protocols do not address. This breath test can confirm or rule it out.
SIBO impairs absorption of key nutrients including iron, B12, and fat-soluble vitamins. Bacterial overgrowth also increases intestinal permeability (‘leaky gut’), allowing endotoxins into the bloodstream that trigger systemic inflammation. The result is persistent fatigue, brain fog, and low energy that blood tests may not explain.
Unexplained low iron, B12, or vitamin D despite adequate diet can indicate SIBO. Overgrown bacteria in the small intestine consume nutrients before your body can absorb them and damage the brush border enzymes needed for absorption. If supplementation is not raising your levels, SIBO may be the reason.
If your gut has never been the same since a bout of food poisoning or gastro, you may have post-infectious SIBO. The original infection can damage the migrating motor complex (MMC) — the ‘cleansing wave’ that sweeps bacteria out of the small intestine between meals — allowing overgrowth to develop and persist.
Research has linked SIBO to rosacea, acne, and eczema through the gut-skin axis. Bacterial overgrowth increases intestinal permeability, allowing inflammatory molecules to enter the bloodstream and trigger skin inflammation. Studies show that treating SIBO can lead to significant improvement in rosacea symptoms.
If probiotics, prebiotic fibre, or fermented foods make your symptoms worse instead of better, SIBO is a likely explanation. These products feed bacteria — and if bacteria are already overgrown in the small intestine, adding more fuel to the fire increases fermentation, gas, and discomfort rather than helping.
Not sure if this test is right for you?
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How it works
From your couch to the lab and back — four simple steps, no doctor visit needed. Your SIBO breath test results arrive in 5–7 business days.
Testing that actually tells you something.
Standard tests check if something is broken. Ours map the ecosystem living inside you.
In partnership with NutriPATH
All results interpreted by qualified microbiome practitioners.
What's inside your report
Your SIBO breath test report maps hydrogen, methane, and combined gas levels across 8 timed collection points over 3 hours — with diagnostic thresholds, gas curves, and clinical interpretation.
| Evaluation | Result | Flag | Threshold |
|---|---|---|---|
| Hydrogen (H₂) change over baseline by 90 min | 17 ppm | <20 ppm | |
| Methane (CH₄) peak at any point | 46 ppm | H | <10 ppm |
| Combined H₂+CH₄ peak | 97 ppm | H | — |
| CO₂ range (sample validation) | 3.3–4.6% | OK | >2.0% |
A methane peak ≥10 ppm at any collection point indicates methane-positive SIBO (IMO). The hydrogen change of 17 ppm is below the 20 ppm diagnostic threshold for hydrogen-dominant SIBO. CO₂ levels confirm valid sample collection.
| Sample | Time | Interval | H₂ (ppm) |
|---|---|---|---|
| S1 (Baseline) | 06:30 | 0 min | 2 |
| S2 | 07:05 | 35 min | 8 |
| S3 | 07:20 | 50 min | 13 |
| S4 | 07:40 | 70 min | 19 |
| S5 | 08:15 | 105 min | 28 |
| S6 | 08:45 | 135 min | 35 |
| S7 | 09:10 | 160 min | 44 |
| S8 | 09:30 | 180 min | 51 |
A rise of ≥20 ppm from baseline by 90 minutes is considered SIBO-positive for hydrogen. Change at 90 min: 17 ppm (below threshold).
| Sample | Time | Interval | CH₄ (ppm) |
|---|---|---|---|
| S1 (Baseline) | 06:30 | 0 min | 4 |
| S2 | 07:05 | 35 min | 8 |
| S3 | 07:20 | 50 min | 15 |
| S4 | 07:40 | 70 min | 21 |
| S5 | 08:15 | 105 min | 28 |
| S6 | 08:45 | 135 min | 33 |
| S7 | 09:10 | 160 min | 40 |
| S8 | 09:30 | 180 min | 46 |
A peak methane level ≥10 ppm at any point indicates methane-positive SIBO (IMO). Peak CH₄: 46 ppm — positive result.
Everything you need to know about SIBO testing
Answers to the questions we hear most from patients considering a SIBO Breath Test.
Book a free discovery call or email us at hello@themicrobiomeclinic.com.au
It measures hydrogen and methane gas levels in your breath at 10 collection points over 3 hours to detect bacterial overgrowth in your small intestine.
The H. pylori test uses a single breath sample to detect one bacterium, while the SIBO test tracks gas patterns across 3 hours to map where and what type of overgrowth is occurring.
You breathe into sealed collection tubes at 20-minute intervals over 3 hours at home — no needles, no clinic visit required.
You'll follow a simple restricted diet for 24 hours before the test and fast for 12 hours overnight.
SIBO results are our fastest — typically ready within 5–7 business days from when the lab receives your sample.
Research suggests up to 78% of people diagnosed with IBS actually have underlying SIBO, so this test could identify the treatable cause behind your diagnosis.
If you have SIBO, the overgrown bacteria in your small intestine ferment these supplements and produce the very gas causing your symptoms.
Yes — hydrogen-dominant SIBO typically presents with diarrhoea while methane-dominant presents with constipation, and each requires a different treatment protocol.