How Is SIBO Diagnosed? Understanding the Breath Test (and Its Limits)
If you're considering testing for SIBO, the hydrogen/methane breath test is the most common method.
How Does It Work?
You drink a sugar solution (usually glucose or lactulose), and your breath is collected at intervals for 2–3 hours. Elevated hydrogen or methane gas indicates bacterial overgrowth in the small intestine.
What It Can Show:
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Type of SIBO (hydrogen, methane)
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Severity of overgrowth
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Transit time through the small intestine
Pros:
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Non-invasive
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Home test kits available
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Provides insight into gas types
Cons:
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Not 100% accurate
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Diet and antibiotics can affect results
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Doesn’t reliably detect hydrogen sulphide SIBO (yet)
Tip for Best Results:
Follow the prep instructions carefully — this usually includes a restricted diet the day before and fasting overnight.
Breath testing isn’t perfect, but it’s one of the best tools we have. Combined with symptoms and a skilled practitioner, it can guide your next steps.