Which breath test measures what
This is the page we would have wanted before spending money on a test.
The short version
Of the 5 breath tests below, 1 measures hydrogen sulfide. The other 4 measure hydrogen and methane only and physically cannot detect the third gas. If hydrogen sulfide is part of your question, a two gas test cannot answer it, and a negative result from one does not rule it out.
This matters because of what people do with a negative. A person suspects overgrowth, buys the cheaper test, gets a negative, and concludes the question is settled. It is not settled. It is unmeasured, and those are different things.
| Test | Hydrogen | Methane | Hydrogen sulfide | Price | Prescription |
|---|---|---|---|---|---|
| trio-smartGemelli Biotech | Yes | Yes | Yes | $349–369verified 2026-08-03 | No |
| SIBO 2-hour / 3-hourGenova Diagnostics | Yes | Yes | No | $225–349verified 2026-08-03 | Yes |
| SIBO breath testCommonwealth Diagnostics International | Yes | Yes | No | $295verified 2026-08-03 | Yes |
| QuinTron breath testQuinTron / breathtests.com | Yes | Yes | No | $195–249verified 2026-08-03 | No |
| SIBO breath testAerodiagnostics | Yes | Yes | No | $299verified 2026-08-03 | Yes |
What each test cannot tell you
- trio-smart
- Measures three gases but cannot tell you what to do about the result. There is no validated hydrogen sulfide threshold in any published guideline; the North American Consensus contains no H2S criterion at all. A number without a threshold is not a diagnosis.
- SIBO 2-hour / 3-hour
- Does not measure hydrogen sulfide. Infers it from a third-hour flatline, which is an unvalidated inference rather than a measurement. A negative result does not rule out hydrogen sulfide overgrowth.
- SIBO breath test
- Does not measure hydrogen sulfide, and says so plainly on its own site.Their own site: “no diagnostic technology on the market can test for H2S at levels of parts per billion”
- QuinTron breath test
- Does not measure hydrogen sulfide. Direct to consumer with no clinician required, which also means no clinician interprets the result for you.
- SIBO breath test
- Does not measure hydrogen sulfide. Their shop subdomain had a TLS hostname mismatch when last checked on 3 Aug 2026; we do not link readers to it until that is fixed.
Not a SIBO test
These devices come up constantly in the same conversations. They measure something real. They do not answer the same question, and we do not list them above because doing so would imply they do.
- FoodMarble AIRE 2 $269 (verified 2026-08-03)
- A personal fermentation tracker, not a diagnostic test. No CLIA lab, no timed consensus protocol, no clinician report. It measures your breath after meals you choose, which answers a different question from a standardised substrate challenge.
Why there is no hydrogen sulfide threshold to compare against
The North American Consensus sets thresholds for hydrogen and methane and contains no hydrogen sulfide criterion at all. So even a three gas test returns a number with no published cutoff behind it. Measuring something is not the same as knowing what counts as abnormal.
That gap is why we describe the three gas test as answering a narrower question than it appears to. It tells you a value. The interpretation of that value rests on work that is still in progress, and the most honest version of this page says so rather than implying a clean cutoff exists.
What we relied on
- Pimentel M et al., American Journal of Gastroenterology 2020 Clinical guidelineNo single symptom can be specifically attributed to SIBO. All six recommendations are conditional, and five of the six rest on very low quality evidence.
- Rezaie A et al., American Journal of Gastroenterology 2017 Clinical guidelineA hydrogen rise of 20 ppm or more over baseline by 90 minutes is positive. Methane of 10 ppm or more at any point is positive. The consensus contains no hydrogen sulfide threshold.
- Scalese G et al., Journal of Clinical Medicine 2025 Peer-reviewed studyClinical symptoms did not significantly differ between SIMO subtypes or between test-positive and test-negative groups. Glucose and lactulose concordance was 8.7%.
- Kashyap P et al., Neurogastroenterology & Motility 2024 Peer-reviewed studyBreath testing is inaccurate and should be abandoned. The methane and hydrogen sulfide criteria have never been validated.