Which SIBO breath test measures hydrogen sulfide?

Of the five tests we track, one measures hydrogen sulfide directly. The others detect hydrogen and methane only and physically cannot register the third gas, so a negative from one of them is not information about hydrogen sulfide.

Is a more expensive breath test better?

Only if the extra money buys a capability you need. The three gas test costs more because it measures an additional gas. If hydrogen sulfide is not part of your question, that capability is not worth the difference to you.

What does a negative breath test actually rule out?

Only the gases the test can measure, at the thresholds published for them. A two gas test returning negative leaves hydrogen sulfide entirely unexamined, and no breath test rules out the several other conditions that produce the same symptoms.

Do I need a prescription?

It depends on the test. Some are sold direct to consumers with no clinician involved, others are practitioner-ordered only. Both arrangements appear in the table above, and direct access also means nobody interprets the result for you.

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.

Prices verified on the date shown against each provider’s own page. A price without a date is a claim about today made from memory.
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. We do not link directly to their storefront; order through a clinician or the provider's main site.

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.

Going deeper on any of these

Hydrogen sulfide testing: one test, no thresholdOne breath test on the US market measures hydrogen sulfide. No published guideline sets a threshold for what the number means. Both facts matter before you buy.
Lactulose or glucose? They agree 8.7% of the timeThe two common breath tests use different sugars and reach different parts of the small intestine. In one study they agreed on 8.7% of cases.
The DAO blood test: not conclusive, widely soldA national allergy guideline says serum diamine oxidase testing cannot be considered conclusive. It remains one of the most commonly sold tests in this space.

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%.We have not yet confirmed a direct link to this document, so we are not giving you one. The citation is enough to find it, and we would rather say this than send you to a journal front page.
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.We have not yet confirmed a direct link to this document, so we are not giving you one. The citation is enough to find it, and we would rather say this than send you to a journal front page.

Common questions

Which SIBO breath test measures hydrogen sulfide?: Of the five tests we track, one measures hydrogen sulfide directly. The others detect hydrogen and methane only and physically cannot register the third gas, so a negative from one of them is not information about hydrogen sulfide.
Is a more expensive breath test better?: Only if the extra money buys a capability you need. The three gas test costs more because it measures an additional gas. If hydrogen sulfide is not part of your question, that capability is not worth the difference to you.
What does a negative breath test actually rule out?: Only the gases the test can measure, at the thresholds published for them. A two gas test returning negative leaves hydrogen sulfide entirely unexamined, and no breath test rules out the several other conditions that produce the same symptoms.
Do I need a prescription?: It depends on the test. Some are sold direct to consumers with no clinician involved, others are practitioner-ordered only. Both arrangements appear in the table above, and direct access also means nobody interprets the result for you.
Is there an agreed threshold for hydrogen sulfide?: No. 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, which is a real limitation rather than a technicality.