Does a positive result mean I should be treated?

That is a clinical decision and it is not automatic. The guideline covering this rates five of its six recommendations as resting on very low quality evidence, and a positive on one substrate frequently comes with a negative on another.

Does a higher number mean a worse case?

The published criteria are thresholds, not severity scales. They were set to divide positive from negative, and no consensus body has established that a larger rise means a more severe problem or a harder one to shift. Reading a number as a grade is a natural thing to do with a lab report and is not supported by what these particular cutoffs are.

Do all labs use the same cutoffs?

The consensus figures are the reference point, but a report will not always tell you which criteria were applied or over what window. That is worth asking, because the same breath sample read against different criteria can produce a different word at the top of the page. The number and its method belong together, and only one of the two is usually printed large.

Reading a breath test result

By BeatSIBO editorial team · Updated August 6, 2026

If you are holding a result, this page is about what the numbers on it are being compared against, and how firm those comparisons are.

The published cutoffs

The short answer

Hydrogen: a rise of 20 parts per million or more over baseline by 90 minutes. Methane: 10 parts per million or more at any point. Both from the North American Consensus. Notice they are different kinds of measurement, a rise within a window against an absolute level at any time, which is worth knowing before comparing them to each other.

Hydrogen
Published cutoff:
Rise of 20 ppm or more over baseline by 90 minutes
Set by:
North American Consensus, 2017
What it does not tell you:
How severe anything is
Methane
Published cutoff:
10 ppm or more at any point
Set by:
North American Consensus, 2017
What it does not tell you:
Whether the level is rising or falling
Hydrogen sulfide
Published cutoff:
None. No consensus body has set one
Set by:
Nobody
What it does not tell you:
Anything, on most tests, because they cannot measure it

Published breath test cutoffs, and the gas that has none
Gas	Published cutoff	Set by	What it does not tell you
Hydrogen	Rise of 20 ppm or more over baseline by 90 minutes	North American Consensus, 2017	How severe anything is
Methane	10 ppm or more at any point	North American Consensus, 2017	Whether the level is rising or falling
Hydrogen sulfide	None. No consensus body has set one	Nobody	Anything, on most tests, because they cannot measure it

These are thresholds, not severity scales. They were set to divide positive from negative, and no consensus body has established that a larger number means a worse problem.

Rezaie A et al., American Journal of Gastroenterology 2017 Clinical guideline

The gas with no threshold

The short answer

Hydrogen sulfide has no criterion in that consensus. None. So a three gas test can give you a hydrogen sulfide value and there is no consensus cutoff to compare it against. The measurement is real; the interpretation is still being worked out at the level of the field.

We put this on the same page as the other two deliberately, because seeing the asymmetry in one place is the point. Two gases have agreed numbers behind them and one does not, and a report printing all three in the same format does not show you that.

Where thresholds come from

These are consensus figures. A group of specialists agreed them, which is a legitimate and normal way to produce a clinical cutoff and is not the same as a number derived from outcome data. That matters most at the margins: a value slightly under a consensus cutoff is slightly under a number that was itself agreed rather than discovered.

What is not settled here

There is an active argument that this testing should not be used for this purpose at all.

Kashyap P et al., Neurogastroenterology & Motility 2024 Peer-reviewed studyWe have not yet confirmed a direct link to this document, so we are not giving you one. The citation above is enough to find it, and we would rather say this than send you to a journal front page.

That position holds the methane and hydrogen sulfide criteria have never been validated. We are not able to settle that and we are not going to present the thresholds as firmer than the people who work with them do.

Why a positive is not a conclusion

Scalese G et al., Journal of Clinical Medicine 2025 Peer-reviewed study

Two things from that work belong next to any result. The two common substrates rarely produced the same diagnosis, so a positive on one is quite likely to sit alongside a negative on the other. And symptoms did not significantly differ between test-positive and test-negative groups, so the result cannot be corroborated by how you feel.

Pimentel M et al., American Journal of Gastroenterology 2020 Clinical guideline

And the guideline itself: all six recommendations conditional, five of six on evidence graded very low quality.

What to do with your result

Take it to a clinician with the substrate used, the timepoints, and any previous result. A number by itself is the least informative version of what you have. A number with its method, next to your history, is a conversation worth having.

Common questions

Does a positive result mean I should be treated?: That is a clinical decision and it is not automatic. The guideline covering this rates five of its six recommendations as resting on very low quality evidence, and a positive on one substrate frequently comes with a negative on another.
Does a higher number mean a worse case?: The published criteria are thresholds, not severity scales. They were set to divide positive from negative, and no consensus body has established that a larger rise means a more severe problem or a harder one to shift. Reading a number as a grade is a natural thing to do with a lab report and is not supported by what these particular cutoffs are.
Do all labs use the same cutoffs?: The consensus figures are the reference point, but a report will not always tell you which criteria were applied or over what window. That is worth asking, because the same breath sample read against different criteria can produce a different word at the top of the page. The number and its method belong together, and only one of the two is usually printed large.