I'm actually getting tested for this next Monday. I have 12 hours of fasting prior. Then at my GI's office they give me a sucrose liquid to drink, then you breathe into something and they measure your bacterial levels. Then if they are not too high, they have you do this either every 15 minutes or every 30 minutes (sorry directions are at home) and test your breath each time.
My GI said that based on all of my symptom descriptions he thinks I have this. If You have a bacterial overgrowth it usually shows up in the first or second breath test he said.
His plan is to put me on a week of antibiotics, then 3 weeks off, then a week on, etc etc