How long should I fast for before I take the small intestinal bacterial overgrowth (SIBO) test?

You need to fast for 8 to 12 hours before you take the test.

Start with a fasting breath sample before you drink the lactulose solution. By 'fasting' you must not eat for 8 to 12 hours before taking the test, but you can drink water.

Most people prefer to take the test first thing in the morning, as they would have naturally fasted overnight.

After taking the first 'fasting' sample, continue to take a series of breath samples at specific timed intervals, according to the full instructions. 

You also must avoid eating during the 2.5 hour test period. 

You also need to follow the test prep diet for a day beforehand, which you can find on the SIBO test kit instructions, along with everything else you need to know.