If you have had a SIBO breath test and seen your results, I bet you are probably wondering what do the results mean for you.

General Interpretation Principles

There are a few general guidelines that are useful in SIBO breath interpretation. The first is humans do not make hydrogen or methane, thus the presence of either on the test is an indication of microorganisms in the gastrointestinal (gi) tract.  Also, while humans do make hydrogen sulfide, excess amounts of hydrogen sulfide on testing indicates microorganisms in the gi tract making excess hydrogen sulfide.

The second guideline that is useful to remember in interpretation of the SIBO breath test is the concept of transient time.  Transient time refers to the time it takes the lactulose solution to get through the small intestine, which is approximately 90 minutes.  Hydrogen gas values that increase by 20 ppm or more within the first 90 minutes of the test are indicative of a positive test for SIBO caused by hydrogen producing microorganisms.

There are different interpretation parameters for methane.  For methane, at any time during the test, if the methane is measured at 10 ppm or greater that is a positive test, and the diagnosis of intestinal methanogen overgrowth (IMO) is made. However, many experienced SIBO clinicians whose patients are experiencing constipation will interpret methane positivity with methane levels at 3 ppm or greater.

Hydrogen sulfide SIBO diagnosis remains a little more nuanced at this time.  There is one test that measures hydrogen sulfide presence directly, while the remainder of the SIBO breath tests only directly measure hydrogen and methane gasses.  The diagnosis of hydrogen sulfide in the absence of direct testing depends upon symptomatology of the patient and the pattern of methane and hydrogen gas patterns.

Straightforward Test Example

In this patient, there is clearly a rise of greater than 20 ppm of hydrogen gas.  There is also clearly greater than 10 ppm of methane gas during the test.  So this patient has both hydrogen SIBO and IMO.  This patient is being treated for both hydrogen and methane SIBO.

Nuanced Test Example

This patient has a lot of gas, bloating and significant constipation.  So while this patient did not have greater than 10 ppm of methane gas during the test, she had 9 ppm of methane gas in the presence of significant constipation.  Thus she was diagnosed and treated for IMO with subsequent improvement.


Testing for diagnostic purposes and retesting after therapy is crucial.  The initial testing identifies the gas or gasses present, thus allowing for the appropriate therapeutic option to be started.  Retesting is very beneficial, especially if symptoms persist or if the initial gas levels were very high.  Retesting allows for the assessment of therapeutic effectiveness and gives information to guide additional therapy.

Remember you are important.  Your health is vital to all you want to do and become.  We at Vytal Health are here to help.

Learn about Dr. Carr