Resources for patients, gastroenterologists and other clinicians using Lactulose Breath Testing results

Note: If you are waiting to have a lactulose breath test and have significant bloating and distension after meals, and have never followed a low FODMAP diet, you can try this. The University of Michigan’s website will guide you to follow this diet. This may help improve your symptoms.

Information for patients with an abnormal lactulose breath test indicating SIBO or IMO

Small intestinal bacterial overgrowth, or SIBO, is not the same in all people. Everyone has a different mix of bacterial species, and the sources of the bacteria, the normal bacterial population of the colon or large intestine and/or the oral bacterial flora, are also different in each person. SIBO can cause no symptoms, symptoms such as bloating, diarrhea, or constipation, or more severe symptoms such as diarrhea with malabsorption and weight loss. There is not a single treatment that is best for all patients, and there is currently no single treatment for SIBO that will “cure” everyone. There are multiple diseases and types of surgical history that can increase the risk for SIBO and medications that reduce stomach acid, for example, can also increase the risk.

There is now a new term for patients with abnormal methane values but normal hydrogen values on lactulose breath testing.   It is Intestinal Methanogen Overgrowth, or IMO, in which there is overgrowth of the methane-producing organism methanobrevibacter smithii, which is actually in a group of organisms slightly different than bacteria called Archaea.

For over 25 years, an abnormal lactulose or glucose breath test meant that there was an abnormal level of either hydrogen or methane or both.  For some time, it has been known that some patients with SIBO also or only produce elevated levels of hydrogen sulfide during a breath test, but this testing was only done by researchers.  Now there is a new breath test for SIBO that measures hydrogen sulfide as well as hydrogen and methane.  This test is called trio-smart, and is available only from Gemelli Biotech, in Irvine, California.  This was developed by Dr. Mark Pimentel and his research group at Cedars-Sinai Medical Center.   The website about this test is

Physicians with MD or DO degrees typically offer antibiotic treatment for SIBO with rifaximin (Xifaxan), and also neomycin or metronidazole for patients who have an elevated methane level.  Treatment for patients with abnormal hydrogen sulfide results on lactulose breath testing is still being studied.  It may be that rifaximin or herbal agents plus the bismuth in the form of bismuth subcitrate 500 mg three times a day is a better treatment for the hydrogen sulfide-positive patients.  Bismuth subcitrate capsules can be prepared by compounding pharmacies; it is not available as an over the counter preparation as it is outside the U.S.  Pepto-Bismol contains sweeteners and  contains the subsalicylate form of bismuth which may cause ringing in the ears in higher doses in some people.  However, 1-2 tbsp 3 times a day will not usually cause such side effects.

Naturopaths, health care practitioners with ND degrees, may help patients receive antibiotics such as rifaximin, but also may treat with a combination of dietary guidance and antimicrobial herbal preparations, perhaps with bismuth subcitrate or Pepto-Bismol as well in patient with hydrogen-sulfide SIBO.  Some MD and DO physicians are offering this treatment to some patients as well.   Another possible initial treatment is a 2 week elemental diet, which is using shakes with simple nutrients that do not require digestion as the sole source of calories. There have been some small studies that have shown improvement in breath test results after 4-6 weeks of certain probiotics, but there are also studies showing no improvement in breath testing for SIBO after probiotics.  Probiotics are not generally used in the treatment of SIBO or IMO.

Rifaximin (Xifaxan) is a special antibiotic that must be dissolved in bile to have its antibacterial effect, and very little of this antibiotic is absorbed into the blood stream. This results in much less of an effect on the normal colonic bacteria than from most other antibiotics. But neomycin and metronidazole do affect the colonic bacteria.   There have been rare cases in which Clostridium difficile colitis has occurred during treatment with rifaximin, but in these cases another broad-spectrum antibiotic was also administered to the patient during the rifaximin treatment. Clostridium difficile or C diff grows in the colon when the normal bacterial flora has been reduced by antibiotic therapy, and can produce very severe diarrhea which can be fatal if it occurs in patients with other serious illnesses. Patients who have had C diff often try to avoid being treated with antibiotics, and may be especially interested in treatment for SIBO or IMO that does not include oral antibiotics.

Experts suggest that it may be best not to limit carbohydrate intake during the initial treatment period to make the antibiotics or herbal treatment better at reducing the bacterial count. After eating a normal varied diet during treatment with antibiotics, herbal preparations, or 2 weeks of elemental diet, patients are advised to follow a diet that is lower in processed or refined carbohydrates, such as foods made from white flour, white rice, pastries, sodas, high-carb snacks, pasta, cakes and cookies, candy, and processed breakfast cereals.  Many patients with SIBO also benefit from some reduction in overall fiber intake.  But it is not clear that there is a single diet that is best for all SIBO patients, and there are differences in the diet recommendations from the experts that I include on this website. Registered dieticians are very familiar with helping people with IBS and SIBO to analyze their usual diets and recommend the most important changes to make. Physicians can refer patients to dieticians, and any fees involved in seeing a dietician are usually very reasonable.

After initial treatment with antibiotics, herbal combinations, or elemental diet, and diet modification, another part of treatment is to improve the motility of the small intestine. The experts in SIBO are in agreement that one of the important causes of SIBO is disturbance the in motility or contraction of the small intestine. In particular, the strong contractions that clear out the small bowel during fasting, called migrating motor complexes or MMCs, are often weaker in people with SIBO.  There is evidence that using either a very small dose of erythromycin (50-62.5 mg) or 0.5 mg prucalopride (which is now available by prescription in the US as a 1 mg or 2 mg pill under the brand name Motegrity) on an empty stomach at bedtime can help prevent recurrence of SIBO symptoms.  Low-naltrexone,  at a dose from 2.5 to 5 mg at bedtime, may also be used for this purpose.  More information is available here about prokinetics .  Eating 3 main meals ideally 4-5 hours apart, but no eating for a few hours before bedtime, and avoiding snacks, provides longer fasting periods and a greater chance that the normal stronger small intestinal contractions that should occur during fasting will occur.

Dr. Mark Pimentel has written an article for physicians about SIBO and treatment with antibiotics and diet.  This is from 2019 and does not include discussion of hydrogen sulfide SIBO.  He is also the lead author of the article ACG Clinical Guideline: Small Intestinal Bacterial Overgrowth in the February, 2020, issue of the American Journal of Gastroenterology.  Dr Pimentel and his colleagues Dr. Ali Rezaie and Dr. Satish Rao published an article about treatment of SIBO (this cannot be downloaded for free but is available through medical libraries or downloading from the publisher for a small fee).  Dr. Pimentel also led a study of the use of elemental diet for initial treatment of SIBO.  The Physician’s Elemental Diet is one example of this, and bags of powder to prepare these shakes can be purchased on-line.  A study from 2013 compared antibiotics to herbal combinations as initial treatment for SIBO.  I created a page listing the herbal preparations from that study with links to purchase the products on  Dr. Allison Siebecker, another SIBO expert, has an excellent website explaining SIBO, herbal treatment and diet which includes an 8-page diet chart.  Note that this chart assumes the reader has read about avoiding all grains as much as possible, as explained on her website under Treatment-Diet.  A page that explains Dr. Siebecker’s herbal treatment options can be found here:  herbal treatment for SIBO.  Another herbal preparation used to treat IMO is Atrantil, a combination herbal product created by a team led by a gastroenterologist, which in some small studies was more effective than placebo in improving symptoms.  Some patients do well following the low FODMAP diet developed by physicians and dieticians at Monash University in Melbourne, Australia.  The GI department at the University of Michigan created a website about the low FODMAP diet to help patients do that.

I hope that this introduction and the resources I have included are helpful to patients and their health care providers as they treat the symptoms of SIBO.

For gastroenterologists and other health care providers treating SIBO:

The documents and website links included here are ones that I have found helpful in deciding how to treat patients with abnormal lactulose hydrogen-methane breath results.  My thanks to Allison Siebecker, ND, one of the creators of the NUNM SIBO Center, Drs. Mark Pimentel and Ali Rezaie and their colleagues at Cedars Sinai Medical Center in Los Angeles, the GI divisions at The Johns Hopkins Hospital in Baltimore, the University Pittsburgh Medical Center,  and the University of Michigan Medical Center in Ann Arbor, and Dr. Kenneth Brown, the developer of Atrantil.

Prokinetics for maintenance of response after initial treatment-3-2021-1

Small intestinal bacterial overgrowth_ Management – UpToDate

Pimentel-_A 14-day elemental diet is highly effective in normalizing the lactulose breath test

How to Order the Physicians Elemental Diet-1

Johns Hopkins-U Pittsburgh Herbal Rx for SIBO article

Links to Amazon-SIBO Herbal Treatments-1

A Siebecker-sibo_specific_diet_food_guide_sept_2014

Herbal treatment for SIBO from Alison Siebecker, ND