Ajax Harwood Clinic
SIBO breath test
Full name: SIBO breath test (lactulose/glucose hydrogen, ± methane, 3-gas)
This test is useful only in specific situations — it's not right for everyone who asks about it.
What this test is
For this test, you drink a sugar solution. Then you breathe into a bag every 15 to 20 minutes for a few hours. It measures hydrogen and sometimes methane gas. This can show if bacteria have overgrown in your small intestine. This is a real condition called SIBO. This test has a real, useful role. It is especially useful if you have had certain bowel surgeries. It is also useful if you have a motility problem. It helps with ongoing bloating and gas that has not improved with treatment. One thing to know: the test is not perfectly accurate. Results can vary depending on how carefully the lab follows the method. A positive result should be read together with your symptoms, not on its own.
Want to see the full clinical reasoning? The reference we use for this test is open to anyone — it is detailed and written for clinicians, and you are welcome to read it.
Open the clinician reference →Looking for other tests, or more on a condition an ND raised? Explore ask.ajaxharwoodclinic.com →
General health information for Ajax Harwood Clinic patients and the public — not medical advice, and not a substitute for seeing your own doctor. Last reviewed 2026-09-23.