The hydrogen/methane breath test is a diagnostic test for the determination of SIBO. You still have a lot of bloating, gas, and stomach discomfort, but your breath test results were negative.

Is it possible to still have SIBO, if your breath test results were negative?

What is a Hydrogen Breath Test and What are the Positives and Negatives Associated with the Test?

The hydrogen/methane breath test is a non-invasive fasting test in which your doctor has you breathe into a machine that monitors excess hydrogen or methane that is released by the opportunistic bacteria in your digestive tract from fermenting an ingested substrate. You are either given glucose or lactulose as a substrate during the test to consume, and exhaled test data is collected at twenty-minute intervals for at least three to five hours. If you produce at least twenty parts per million (ppm) of hydrogen or three ppm of methane after the first thirty to sixty minutes and before the last test markers, you test positive for active SIBO (but even a result of twelve ppm hydrogen should be treated at the very minimum). If your hydrogen and methane are flat-lined or do not rise during the test, you may have the third type of SIBO, hydrogen sulfide producing bacterial dysbiosis.1

It is debatable about which substrate is better at determining SIBO, lactulose, or glucose? Lactulose is a synthetic, non-digestible sugar that is used in the treatment of constipation and to reduce ammonia burden in people suffering from liver disease. Lactulose is a disaccharide formed from one molecule of fructose and galactose. Bacteria have to ferment lactulose in our intestinal tract first for any to be absorbed. We lack the necessary enzymes to metabolize lactulose ourselves. Lactulose use is only by prescription in the United States. Glucose is a simple sugar (monosaccharide) directly absorbed by our gastrointestinal system and is easily metabolized by our body. The use of glucose as a test marker may give a false negative reading because at least seventeen feet of the small intestine may not be tested because the glucose might be absorbed before it reaches the distal part of the small intestine to see if it is fermented by bacteria. Furthermore, people dealing with hydrogen dominant SIBO with diarrhea (fast motility), glucose, or lactulose might reach the cecum (the first part of the large intestine) quicker, creating a false positive SIBO result in people with strictly colonic overgrowth. If your hydrogen and methane levels are normal until the last few timed intervals at the end of the test and you suffer from normal motility or SIBO-D then you might not have SIBO but colonic dysbiosis depending on how elevated your test markers are and if you have lower abdominal bloating.2 3 4 5 6

There are some issues with the use of lactulose as well as a substrate. Not all strains of bacteria/archaea ferment lactulose, which may cause a false-negative test result. Lactulose decreases bowel transit time as an osmotic laxative, which may also skew the test results. It might be best to perform both tests if possible (glucose and lactulose) to accurately determine if you have SIBO. Finally, it may be best to have a bowel transit test done as well, like a sitz marker test to determine one’s motility and how long it will take the substances to reach the large intestine.7 8 9 10

The Following are Possible Testing Outcomes:

Your test results show elevated hydrogen (at least twelve ppm) during the beginning of the test. You might be dealing with upper gut dysbiosis of hydrogen-producing bacteria.

Your test results show elevated hydrogen (at least twelve ppm) during the beginning and the middle of the test. You might be dealing with upper gut dysbiosis and SIBO-D from hydrogen-producing bacteria.

Your test results show elevated hydrogen (at least twelve) ppm during the middle of the test. You might be dealing with upper gut dysbiosis and SIBO-D from hydrogen-producing bacteria.

Your test results show elevated hydrogen (above fifty ppm and symptomatic with bloating) at the end of the test. You might be dealing with colonic dysbiosis from hydrogen-producing bacteria.

Your test results show elevated hydrogen (at least twelve ppm) throughout the entire test. You might be dealing with digestive tract dysbiosis from hydrogen-producing bacteria.

Your test results show elevated hydrogen and methane during the beginning of the test, but the gases decrease over time. You might be dealing with upper gut dysbiosis of hydrogen-producing bacteria and methane-producing archaea and possibly SIBO if it maintains elevation during the middle of the test.

Your test results show elevated hydrogen during the beginning of the test. Hydrogen decreases, and methane starts to increase in the middle of the test. You might be dealing with upper gut dysbiosis of hydrogen-producing bacteria and methane-producing archaea dominant SIBO-C.

Your test results show a flat line (all zeroes) of gas production throughout the test. You might be dealing with hydrogen sulfide dysbiosis of the entire digestive tract.

Your test results only show a flat line (all zeroes) of gas production during the middle of the test results. You might be dealing with hydrogen sulfide SIBO.

Your test results only show a flat line (all zeroes) of gas production during the end of the test results. You might be dealing with hydrogen sulfide colonic dysbiosis.

Remember, for most people suffering from archaea dysbiosis, you are probably suffering from hydrogen-producing bacterial dysbiosis as well upstream within your digestive tract because they produce hydrogen that archaea consume, which would decrease the hydrogen you exhale during a breath test.

The Following is a Link to Recommended Guidelines Before Breath Testing.

People can still have symptoms of SIBO, and both tests come back negative. How can that be?

Again, not every type of bacterial overgrowth within the gut will contain bacteria that produce hydrogen from fermentation, so these tests could be inaccurate in determining SIBO. There is also no unified medical interpretation of SIBO breath tests. Therefore, a doctor might perceive your test results as normal, and they are not, you have SIBO. If your values do not rise during the test, you may have hydrogen sulfide producing bacterial dysbiosis within the small intestine. A test to determine hydrogen sulfide dysbiosis will hopefully be out soon, and in widespread use, it has been in development for years. I recommend using the guidelines of hydrogen/methane breath interpretation by the leading SIBO expert, Dr. Allison Seibecker.11 12 13

I recommend getting a GI MAP stool test performed by Diagnostic Solutions through your gastroenterologist. I can help interpret the results of your bacterial culture, lactoferrin levels, pH, and antibody levels to determine if you have SIBO. Contact me for Health Coaching if you are interested.

It is best to tackle your SIBO if you have many of the symptoms of SIBO, instead of relying on breath test results. If you are not any better within a month of following the FODMAP diet and SIBO protocols then SIBO was either not your problem in the first place (might be a yeast issue instead or SIYO), or the protocol was not strong enough to eliminate some hardy bacteria including MAP or Klebsiella.