Which is better — a lactulose or glucose SIBO test?

Neither is universally better. Lactulose surveys the full small intestine; glucose focuses on the upper portion. Practitioners choose based on the clinical question, and many at-home kits use lactulose.

What does methane on a SIBO test mean?

Methane is produced by archaea rather than bacteria, and elevated methane is discussed under the term intestinal methanogen overgrowth (IMO). It's associated with a constipation-leaning symptom pattern and is interpreted by your practitioner alongside hydrogen results.

How long does a SIBO breath test take?

Typically two to three hours on test morning, collecting breath samples at fixed intervals after drinking the test solution — plus a prep diet the day before and an overnight fast.

Types of SIBO Breath Tests

Not all SIBO breath tests are identical. Two choices define most kits: which test sugar you drink, and which gases the lab measures. Here's what each difference means in plain English.

Lactulose vs. glucose

Lactulose isn't absorbed by the body, so it travels the full length of the small intestine — which is why lactulose tests aim to survey the whole small bowel and typically run longer, with samples collected over two to three hours. Glucose is absorbed early in the small intestine, so glucose tests focus on the upper portion and may run shorter. Practitioners choose between them based on what they want to see; many at-home kits use lactulose for its full-length view.

Hydrogen and methane

Different gut organisms produce different gases. Hydrogen comes from bacterial fermentation. Methane comes from archaea — organisms that consume hydrogen and release methane — and elevated methane has its own associated symptom pattern, often constipation-leaning, now commonly discussed under the term intestinal methanogen overgrowth (IMO). Modern tests typically measure both gases from the same breath samples, which is worth confirming when comparing kits.

What the schedule looks like

Whatever the sugar, the structure is the same: a baseline breath sample before drinking the solution, then samples at fixed intervals — commonly every 15 to 20 minutes — for the test's duration. The lab plots gas levels over time, and the shape and timing of any rise is what a practitioner interprets.

Choosing well

The practical checklist when evaluating any SIBO breath test: which sugar it uses, whether it measures both hydrogen and methane, how many samples it collects, and whether results are reviewed with a practitioner. When kits are available here, those details will be stated plainly — join the waitlist to be notified.

Frequently asked questions

Which is better — a lactulose or glucose SIBO test?: Neither is universally better. Lactulose surveys the full small intestine; glucose focuses on the upper portion. Practitioners choose based on the clinical question, and many at-home kits use lactulose.
What does methane on a SIBO test mean?: Methane is produced by archaea rather than bacteria, and elevated methane is discussed under the term intestinal methanogen overgrowth (IMO). It's associated with a constipation-leaning symptom pattern and is interpreted by your practitioner alongside hydrogen results.
How long does a SIBO breath test take?: Typically two to three hours on test morning, collecting breath samples at fixed intervals after drinking the test solution — plus a prep diet the day before and an overnight fast.

At-home SIBO testing is coming to this site.

Join the waitlist and you'll be the first to know when kits are available — plus get our free prep guide so you're ready to test correctly on day one.

This site is for educational purposes only and is not medical advice, diagnosis, or treatment. If you have digestive symptoms, talk with your healthcare provider about whether testing is right for you.