InstalabSIBO Panel
Should you take a SIBO Panel test?
This test is most useful if any of these apply to you.
3 biomarkers included
- Peak Hydrogen (H₂)Tracks fermentation by bacteria in your small intestine. A rise after the sugar drink is the classic signal of small intestinal bacterial overgrowth, the pattern most often tied to diarrhea and bloating.A hydrogen rise of at least 20 parts per million by 90 minutes points to bacterial overgrowth as a driver of your symptoms.
- Peak Methane (CH₄)Tracks methane-making archaea, a separate group of microbes a hydrogen-only test misses. Because they consume hydrogen, measuring methane catches overgrowth that would otherwise read as a false negative.Methane at or above 10 parts per million signals methanogen overgrowth, the pattern most closely linked to constipation and slow transit.
- Peak H₂ + CO₂Pairs hydrogen with carbon dioxide, the gas from deep in your lungs. Because deep breath holds steady carbon dioxide, this reading helps confirm the sample was collected correctly rather than diluted with mouth air.A low carbon dioxide reading flags a diluted sample, warning that a normal-looking hydrogen result may actually be falsely low.
About SIBO Panel
Bloating, gas, and unpredictable bowel habits are among the most common reasons people sense something is off with their gut, yet routine tests often come back clean. One reason is that standard workups rarely look at where microbes are actually living in your digestive tract. This panel does.
After you drink a measured sugar solution, microbes in your small intestine ferment it and release gases that cross into your blood and turn up in your breath. By capturing those gases over roughly two hours, this panel shows whether that fermentation is happening where it should not be.
What This Panel Reveals
Your small intestine is meant to stay relatively low in microbes. When bacteria or a separate group of microbes called archaea grow there in excess, they ferment your food and produce gases your own cells cannot make. Measuring those gases is an indirect way to detect that overgrowth without a scope or surgery.
The hydrogen reading tracks fermentation by bacteria. A meaningful rise points to small intestinal bacterial overgrowth (called SIBO), a pattern more often tied to diarrhea and urgency.
The methane reading tracks a different culprit: methane-making archaea, led by a species called Methanobrevibacter smithii. High methane points to intestinal methanogen overgrowth (called IMO), which is linked to constipation and slower transit. Because these archaea consume hydrogen to make methane, a hydrogen-only test can read falsely low in these people. Measuring both is what catches them.
The third reading pairs hydrogen with carbon dioxide (the gas you normally breathe out). Deep breath from your lungs holds a fairly steady amount of carbon dioxide, so this measurement helps confirm your sample came from deep breath rather than diluted mouth air, and it can flag a falsely low hydrogen value caused by poor sampling. This sample-quality check is emphasized in breath-testing reviews more than in major society guidelines.
How to Read Your Results Together
Guidelines read a hydrogen rise of at least 20 parts per million (a measure of gas concentration, abbreviated ppm) by 90 minutes as positive for bacterial overgrowth, and methane at or above 10 ppm at any point as positive for methanogen overgrowth. The value of the panel is the pattern across all three.
| Your Pattern | What It Suggests |
|---|---|
| High hydrogen rise, normal methane | Bacterial overgrowth (SIBO), more often linked with diarrhea |
| Normal hydrogen, high methane | Methanogen overgrowth (IMO), more often linked with constipation |
| Both elevated | A mixed pattern; both microbial groups are active |
| Low carbon dioxide on a normal-looking test | Sample may have been diluted, so the gas values could read falsely low |
What to Do with Your Results
A positive result is a reason to work with a gastroenterologist on next steps, not a diagnosis to act on alone. In people with diarrhea-predominant irritable bowel syndrome (a common gut-brain disorder abbreviated IBS), a positive hydrogen breath test predicted a better response to the antibiotic rifaximin: 59.7% of positive patients improved versus 25.8% of negative patients. Methane-predominant patterns often respond less well to that single antibiotic and may call for a different approach.
If your result is positive, check for downstream effects and overlapping conditions, since overgrowth can impair absorption of vitamin B12 and iron, and celiac disease can produce nearly identical symptoms. When you retest to confirm treatment worked, use the same sugar and the same preparation both times, because results shift with diet, recent antibiotics, and how the sample is collected.
When Results Can Be Misleading
These readings are useful surrogates, not proof. The most important confounder affects the whole panel at once: if the sugar solution moves quickly into your large intestine, the normal microbes there ferment it and produce a gas rise that mimics small intestinal overgrowth without actually being it.
Preparation matters for every reading. Antibiotics within the prior four weeks, laxatives or promotility drugs within the past week, a high-fiber meal the day before, or smoking on test day can all shift your gases. Compared against laboratory sampling of intestinal fluid, breath testing catches only about half of true cases (pooled sensitivity 42.0% for lactulose and 54.5% for glucose), so a negative result does not fully rule overgrowth out.