SIBO (Small Intestine Bacterial Overgrowth) Breath Test


Is the SIBO breath test the right laboratory test for you?

In our experience, many persons having digestive symptoms receive a diagnosis of irritable bowel syndrome (IBS), but no particular guidance in identifying possible causes, or options for treatment other than symptom management (e.g., laxatives). SIBO (Small Intestinal Bacterial Overgrowth) breath testing may be the first step to understanding your digestive symptoms, and taking action at the “root cause” level.

Although this test is commonly referred to as SIBO breath testing, it may also be used to diagnose carbohydrate (sugar) malabsorption.

This laboratory test is used primarily to identify possible causes of:

  1. Unexplained irritable bowel syndrome (IBS) symptoms1 (abdominal pain, bloating, gas; diarrhea and/or constipation; mucous in stool2)
  2. Unexplained abdominal bloating3

Other health conditions associated with SIBO include:

  • Weight loss1
  • Anemia1
  • Malnutrition1
  • Hypothyroidism
  • Fibromyalgia1
  • Parkinson’s disease1

Specifically, this test diagnoses:

  1. Overgrowth of bacteria in the small intestine, or migration of bacteria from the large intestine to the small intestine3

  2. Carbohydrate (sugar) malabsorption3

How does SIBO breath testing work?

Breath testing relies on measurement of gases produced in the intestines that diffuse into the bloodstream and are ultimately expired through the lungs.3

Two of the main gases found in the breath, and produced exclusively by microbial fermentation of carbohydrates, are hydrogen and methane.3

Excess hydrogen and/or methane will be produced if excessive gut bacteria cause excessive fermentation of carbohydrates, either:

  1. In the small intestine because of small intestine bacterial overgrowth (SIBO)4, or
  2. Malabsorption of carbohydrates in the small intestine, allowing excessive carbohydrate to progress to the large intestine (colon), where there is excessive fermentation by bacteria.4

Basically: expired air is collected, and if it contains excessive hydrogen or methane, the only possible causes are excessive fermentation of carbohydrates by bacteria, either in the small or large intestine (depending on the timing of the higher than normal readings).

How does this SIBO breath test compare with other assessment options?

At Toronto-Centre for Naturopathic Medicine, we use BioHealth Laboratory’s test for SIBO breath testing, which is the most comprehensive option available to naturopathic doctors in Ontario.

The BioHealth Laboratory test:

  1. Measures both expired hydrogen and methane, and
  2. Offers testing using any combination of lactulose, glucose and fructose as test substrates.

These are important considerations, as:

  • 15% or more persons will produce methane rather than hydrogen   with microbial fermentation of carbohydrates. Tests measuring only hydrogen may result in a “false-normal” result for these persons.5
  •  Although measuring glucose fermentation alone is more sensitive (i.e., less likely to miss a diagnosis) than measuring lactulose fermentation alone in assessment of SIBO4, measuring both offers the most accurate assessment of gut bacteria status. Glucose is completely absorbed in the first section of the small intestine4, lactulose is absorbed throughout the small intestine, including the later portion of the small intestine6 and large intestine.Measurement of both allows for the most sensitive assessment of SIBO the first section of the small intestine; (slightly less sensitive) assessment of the later portion of the small intestine; and carbohydrate malabsorption resulting in excessive fermentation in the large intestine. 
  • Fructose malabsorption, although poorly understood as related to digestive symptoms, has been demonstrated to relate to increased severity of IBS symptoms.1

Importantly, breath testing is more reliable for “ruling in” SIBO than “ruling out” SIBO – if breath testing demonstrates you have SIBO, you almost certainly do; if breath testing suggests you do not, you probably do not, but be open to the possibility the test is incorrect.4

Other methods for assessing possible SIBO are:

  1. Bacterial culture – the most direct method, considered by some to be the “gold standard” (other experts are of the opinion no “gold standard” exists for diagnosis of SIBO4), but inconvenient to the patient, and prone to “false-normal” (i.e., incorrectly “ruling out” SIBO) results and contamination in the sampling process1, 4
  2. Urine organic acids testing (OAT) – sometimes suggested as an assessment option, but not diagnostic for SIBO7
  3. Stool analysis – sometimes suggested as an assessment option, but not diagnostic for SIBO7

How can you ensure the most accurate result possible?

Different laboratories suggest different (or no) guidelines for preparing for breath testing, but according to guidelines established in the 2017 Hydrogen and Methane-Based Breath Testing in Gastrointestinal Disorders: The North American Consensus statement3, in order ensure the most accurate result possible:

  1. Antibiotics should be avoided for four weeks prior to breath testing.
  2. (If possible), promotility drugs and laxatives should be stopped at least one week prior to breath testing.
  3. Fermentable foods such as complex carbohydrates should be avoided on the day prior to breath testing.
  4. A fasting period  of 8 to 12 hours prior to breath testing.
  5. Smoking should be avoided on the day of breath testing.
  6. Physical activity should be limited during breath testing.
  7. Discontinuation of proton pump inhibitors prior to breath testing is not necessary.

What is the procedure for SIBO breath testing?

This test is conducted at home with a provided test kit.

  1. Beginning 24-hours before beginning the testing procedure, the specified diet must be followed.
  2. Beginning 12-hours before  beginning the testing procedure, the patient must fast.
  3. A baseline breath sample is collected.
  4. The glucose, lactulose or fructose mixture is consumed.
  5. Breath samples are collected every 15-minutes following mixture consumption until all 9 to 12 vials are filled (135 to 180 minutes, depending on test conducted).

In a nutshell:

  1. Consider this laboratory assessment if you have been diagnosed with IBS, or have digestive symptoms, with no identifiable cause.
  2. Measurement of both hydrogen and methane (as opposed to hydrogen only) allows for the  most accurate assessment of SIBO and carbohydrate malabsorption.
  3. Hydrogen/methane breath test using lactulose-only as a test mixture is more affordable (compared to lactulose and glucose test mixtures), and although slightly less sensitive, more reliably assesses the entire length of the small intestine.
  4. Testing for fructose malabsorption may be considered if suffering from severe IBS symptoms.
  5. This test is non-invasive, conducted at home, and requires up to three hours to complete.

Jonah Lusis, ND


  1. Simrén M, Stotzer PO. Use and abuse of hydrogen breath tests. Gut. 2006;55(3):297-303. Available at:
  2. Mayo Clinic [Internet]. Irritable bowel syndrome. [cited 2018 Nov 23]. Available at:
  3. Rezaie A, Buresi M, Lembo A et al. Hydrogen and methane-based breath testing in gastrointestinal disorders: the North American consensus. Am J Gastroenterol. 2017;112(5):775-784. Available at:
  4. Ghoshal UC. How to interpret hydrogen breath tests. J Neurogastroenterol Motil. 2011;17(3):312-7. Available at:
  5. deLacy Costello BP, Ledochowski M, Ratcliffe NM. The importance of methane breath testing: a review. J Breath Res. 2013 Jun;7(2):024001. doin:10.1088/1752-7155/7/2/024001.
  6. BioHealth Laboratory [Internet]. Small intestinal bacterial overgrowth (SIBO) breath testing.  [cited 2018 Nov 23]. Available at:
  7. Siebecker A, Sandburg-Lewis S. SIBO: the finer points of diagnosis, test interpretation, and treatment. Naturopathic Doctor News and Review [Internet]. 2014 Jan 7 [cited 2018 Nov 23]. Available at:



Posted: 2018 Nov 23