Hydrogen Breath Test Preparation for Bacterial Overgrowth

The breath test for bacterial overgrowth allows the doctor to see the amount of bacteria growing in the small intestines. Large number of bacteria will compete for nutrients which will not allow the body to absorb enough nutrients. The breakdown of nutrients by the bacteria can also damage the cells lining the intestinal wall.

The procedure involves fasting (not eating or drinking) before the test and then drinking a dose of lactutose syrup. Breath samples will be given every 15 minutes until 12 samples are given.

The hydrogen breath test cannot be done following a colonoscopy, barium enema, or any tests that require a bowel prep to be given. The bowel prep will cleanse the bacteria.


It is important that you have not received antibiotics or probiotics for at least 2 weeks before the test.

It is a important not to have had severe diarrhea recently. If either one of these conditions apply to you please inform your doctor before starting the test.

Other preparations to follow:

  • FOLLOW the low fiber/low residue diet for three days prior to your breath test for bacterial overgrowth.
  • DO NOT smoke for six hours prior to the test. Smoking can affect the results of the test.
  • DO NOT exercise or chew gum an hour before the test.
  • DO NOT use Imodium, Lomotil, or any product which slow the bowel.
  • DO NOT EAT OR DRINK anything after midnight the night before your test.

If you have any questions or concerns you may contact the nurse in the Endoscopy office at 860-679-4784.

Day of Procedure

You should be ready to go home approximately three hours after your arrival for the test.

Important Notes

  • Follow instructions carefully.
  • Three to seven days before the test, you will receive a call to confirm the appointment. If you do not receive the call please call 860-679-4784.