What is the best test for small intestinal bacterial overgrowth?

What is the best test for small intestinal bacterial overgrowth?

Small intestinal bacterial overgrowth (SIBO) can cause many IBS symptoms like gas, bloating, diarrhea, constipation and abdominal pain.  The best test for SIBO is a breath test, but there are two different types of breath tests.  Let’s discuss which one you should you get?


Dr. Michael Ruscio, DC: Hi, this is Dr. Ruscio. And if you’re not familiar with small intestinal bacterial overgrowth, or SIBO for short, this may be responsible for many of the symptoms of IBS — gas, bloating, abdominal pain, altered bowel frequency (meaning constipation or diarrhea). And so this is a condition. IBS affects about 10% of the population. So it’s a fairly common condition. And small intestinal bacterial overgrowth or SIBO may underlie many cases of IBS.

[Continue reading below]


DrMR: Now, this can be tested via a breath test. But there are two different types of breath tests that are typically used. There is a lactulose test. And there is a glucose test. And there is controversy as to which one is the best. And so I thought we could talk briefly about the pros and the cons to help you or your doctor determine what the best test might be for you.

“Small intestinal bacterial overgrowth or SIBO may underlie many cases of IBS.”

Now, lactulose is kind of the favored test right now, you could say, in the SIBO community. And there’s something to be aware of with lactulose that I think is very important. Lactulose produces what’s called false positives, meaning the tests show SIBO, but the person doesn’t actually have SIBO. So they’re positive for the test, but they’re falsely positive. It’s a false positive test.

The reason for this is because lactulose makes its way all the way through the small intestine and then into the large intestine. Now, as that lactulose is traveling through the small intestine, the gas reading that we see as a byproduct of that should be low. But when it gets into the large intestine, the gas level should elevate.

SIBOHowever, if for some reason, that lactulose makes its way through the small intestine too quickly and gets into the large intestine during the time period when we think it should be in the small intestine, that will give us a false positive elevation of gas. And this has been consistently shown in many of the studies that the lactulose seems to produce what’s called false positives.

Now, the merit to the lactulose test is that because it travels all the way through the small intestine, it gives you a good indication of what’s happening at the end of the small intestine where small intestinal bacterial overgrowth may be more common. But we have to counterbalance that with the fact that false positives occur.

False Positives

What this means if you’re a patient being treated for SIBO or if you’re a doctor treating a patient for SIBO is that if someone tests positive with lactulose, you treat them, their symptoms improve, but their labs don’t, there’s a probability that that person may not be a good person to use lactulose with. And you may be seeing a false positive test. And we’ve actually talked with patients like that in our newsletter in the past. So it’s very important to keep that in mind.

Now, glucose does not produce the same false positives. So with glucose, if you see a positive, you can rest assured that’s a true positive. The negative aspect of glucose is that it does not make its way all the way to the end of the small intestine in most cases. And if there’s SIBO at the end of the small intestine, you may miss it on glucose testing.

So both these tests have merit. It’s just important that we understand the pros and the cons of each. Lactulose will overreport SIBO, or cause false positives. Glucose may underreport SIBO. However, when we look at the studies, the studies seem to favor glucose, in my opinion, in terms of giving us the most accurate gauge.

In any case, either test can be used. It’s just important you work with a doctor who’s well trained and knows how to interpret these tests and, more importantly, will interpret these tests cautiously.

There certainly seems to be this belief on the internet that you can never get over SIBO. And I think a lot of that has to do with the high use of lactulose testing and people not having the guidance of a good clinician. If someone has symptoms of SIBO, they’re treated for SIBO, and their symptoms get a lot better but their labs stay normal, and they’re using lactulose, I look at that like a false positive or that they don’t have SIBO. And now we can stop treating you because you feel better.

So again, both these tests have merit. If you look at our website, we recently did a podcast, which is fully transcribed, where we went through the studies on this issue point by point and really picked into the details.

But from a big picture perspective, both tests can be used. Lactulose will give false positives, so you have to be aware of that. Glucose seems to be more accurate, but it may miss some cases.

Additional Tips

One other tip I should mention — or two other tips — and one reiteration is that if you’re using lactulose with someone, you test them for SIBO, they’re positive, you treat SIBO, their symptoms get much better or go away, and then you retest them and they still have SIBO via lactulose testing, I would be very suspect of a false positive.

Also, with lactulose, if you only see positive SIBO at the very end of the test at maybe 100 or 120 minutes, if that’s the only positive point you see with lactulose, I’d be suspicious that that might be a false positive because if the lactulose makes its way through the small intestine quickly in that person because it may be acting as an irritant or a laxative for them or they have a congenitally shorter small intestine as some do — and many Asians actually do — then you may get a false positive.

With glucose, if you see positive SIBO, you can rest assured that that’s a true positive. However, there is a possibility that that test could be negative. And if the person still has symptoms, you may have missed a SIBO infection at the very end of the intestines. And that person, you may want to treat and then evaluate how they’re doing. If they respond well, then you’ve kind of affirmed that SIBO was actually there.

Both tests can be used. Both tests have merit. I personally use both. It’s just important to be aware of the pros and the cons.

So this is Dr. Ruscio. And I hope this information helps you get healthy and get back to your life. Thanks!

What do you think? I would like to hear your thoughts or experience with this.

Dr. Ruscio is your leading functional and integrative doctor specializing in gut related disorders such as SIBO, leaky gut, Celiac, IBS and in thyroid disorders such as hypothyroid and hyperthyroid. For more information on how to become a patient, please contact our office. Serving the San Francisco bay area and distance patients via phone and Skype.

Discussion

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34 thoughts on “What is the best test for small intestinal bacterial overgrowth?

  1. Thanks for this! I’m a nutritionist in an internal medicine practice. We’ve just started using Commonwealth Labs lactulose test for many of our patients, making sure to have them do the prep diet. Out of 10 that we have run in the past 6 months, 8 have been ZEROS on hydrogen and minimal rises over baseline in methane (still enough to be positive for Pimentel). Commonwealth says that this only happens in 5% of the tested population, so why am I seeing so many in my small population? I understand that methagens consume hydrogen producing bacteria so this could account for the results. Are you seeing an increase in this patterns in your practice? I’ve also had one patient with zeros across the board. I’ve heard that hydrogen sulfide producing bacteria could be to blame. Do you see this often?

    1. Hi Keri,
      Interesting. I can’t say I see this often but its also important to understand that meticulous analysis of the results are not required, at least not in my opinion. It’s hard to speak to this here because there is a lot to say. Just remember that the testing does not always predict response to treatment so its good not be limited to only treating based upon test results.

  2. Thanks for this! I’m a nutritionist in an internal medicine practice. We’ve just started using Commonwealth Labs lactulose test for many of our patients, making sure to have them do the prep diet. Out of 10 that we have run in the past 6 months, 8 have been ZEROS on hydrogen and minimal rises over baseline in methane (still enough to be positive for Pimentel). Commonwealth says that this only happens in 5% of the tested population, so why am I seeing so many in my small population? I understand that methagens consume hydrogen producing bacteria so this could account for the results. Are you seeing an increase in this patterns in your practice? I’ve also had one patient with zeros across the board. I’ve heard that hydrogen sulfide producing bacteria could be to blame. Do you see this often?

    1. Hi Keri,
      Interesting. I can’t say I see this often but its also important to understand that meticulous analysis of the results are not required, at least not in my opinion. It’s hard to speak to this here because there is a lot to say. Just remember that the testing does not always predict response to treatment so its good not be limited to only treating based upon test results.

  3. “What the study does tell us is that criteria being applied to indicate a high chance of the presence of SIBO in IBS subjects are questionable, supporting other evidence of poor performance characteristics of the LBT. The data do not tell us that the LBT should be used to identify patients for antibiotic therapy as even the worst performing groups had a near 50 % response rate and those with “normal” LBT findings were not treated”

    https://link.springer.com/article/10.1007/s10620-015-3956-6.

  4. “What the study does tell us is that criteria being applied to indicate a high chance of the presence of SIBO in IBS subjects are questionable, supporting other evidence of poor performance characteristics of the LBT. The data do not tell us that the LBT should be used to identify patients for antibiotic therapy as even the worst performing groups had a near 50 % response rate and those with “normal” LBT findings were not treated”

    https://link.springer.com/article/10.1007/s10620-015-3956-6.

  5. For the past year off n on I have been experiencing sulfur burps, nausea , vomiting sometimes and always diarrhea. We have figured out that every episode causes my white count to be high. (16 to 24, 000) I have had a EGD and biosphies are normal. Stool testing , celiac testing , everything normal. I’m seeing a Specialist and he’s thinking bacteria overgrowth . Dr has me on a digestive pill twice a day and probiotic. Also on fodmap diet with no gluten. Seems like it’s helping but only been on it for 3 weeks. I just need answers and a fix. I’m a teacher and teach second graders . At first we though these were viral but there not. One year ago my primary Dr put me on flagel & cipro and I had no more episodes for 4 months with no diet of any kind.. I weigh 114 and can’t afford to lose any weight. Any advice would be appreciated.

    1. Hi Kolby,
      It sounds like you might benefit from a course of herbal antimicrobials. My book lays out a self-treatment plan for exactly how to do this. I would give this a shot. Make sure to run this by your doctor first.

  6. For the past year off n on I have been experiencing sulfur burps, nausea , vomiting sometimes and always diarrhea. We have figured out that every episode causes my white count to be high. (16 to 24, 000) I have had a EGD and biosphies are normal. Stool testing , celiac testing , everything normal. I’m seeing a Specialist and he’s thinking bacteria overgrowth . Dr has me on a digestive pill twice a day and probiotic. Also on fodmap diet with no gluten. Seems like it’s helping but only been on it for 3 weeks. I just need answers and a fix. I’m a teacher and teach second graders . At first we though these were viral but there not. One year ago my primary Dr put me on flagel & cipro and I had no more episodes for 4 months with no diet of any kind.. I weigh 114 and can’t afford to lose any weight. Any advice would be appreciated.

    1. Hi Kolby,
      It sounds like you might benefit from a course of herbal antimicrobials. My book lays out a self-treatment plan for exactly how to do this. I would give this a shot. Make sure to run this by your doctor first.

  7. My daughter recently saw a Functional Medicine Dr. for long standing, debilitating health issues. The Dr. suspected SIBO immediately. She ran a battery of tests, but we have yet to do the breath tests due to increased anxiety about the restrictiveness of the test and the lactulose. My daughter has a long standing history of an eating disorder and she can not afford to lose a pound. She is also lactose intolerant. Is there a way of doing the test without restiction of calories? How much oil or fat can you consume the day before without skewing the results? I would like her to do the test before taking on a course of antibiotics and supplements. Her microbiome is already very low for good bacteria in her gut and she is dealing with candida overgrowth.

  8. My daughter recently saw a Functional Medicine Dr. for long standing, debilitating health issues. The Dr. suspected SIBO immediately. She ran a battery of tests, but we have yet to do the breath tests due to increased anxiety about the restrictiveness of the test and the lactulose. My daughter has a long standing history of an eating disorder and she can not afford to lose a pound. She is also lactose intolerant. Is there a way of doing the test without restiction of calories? How much oil or fat can you consume the day before without skewing the results? I would like her to do the test before taking on a course of antibiotics and supplements. Her microbiome is already very low for good bacteria in her gut and she is dealing with candida overgrowth.

  9. I was diagnosed with ibs 3 years ago I have tried many prescribed drugs hypothesis therapy and diets nothing has worked for me my main troubling symptoms are constant build up of gas and bloating.could sibo be the underlying cause? So frustrating living with chronic pain.

    1. It could be Charlotte. I would go through the protocol contained in my book. Sounds like you have explored some options but I am willing to bet the book protocol provides some you have not yet heard of and that could help. Good luck 🙂

  10. I was diagnosed with ibs 3 years ago I have tried many prescribed drugs hypothesis therapy and diets nothing has worked for me my main troubling symptoms are constant build up of gas and bloating.could sibo be the underlying cause? So frustrating living with chronic pain.

    1. It could be Charlotte. I would go through the protocol contained in my book. Sounds like you have explored some options but I am willing to bet the book protocol provides some you have not yet heard of and that could help. Good luck 🙂

  11. Hi Dr. Ruscio, Thanks for sharing the great information. Do you have a recommendation of an online supplier that I could use to order the SIBO test for myself (as a patient)? It’s hard to determine what suppliers are the best without some feedback from those who have used it in their practice/with patients. Thanks so much!

  12. Hi Dr. Ruscio, Thanks for sharing the great information. Do you have a recommendation of an online supplier that I could use to order the SIBO test for myself (as a patient)? It’s hard to determine what suppliers are the best without some feedback from those who have used it in their practice/with patients. Thanks so much!

  13. Hi Dr Ruscio. I’m having Hydrogen Breath test and have to stick to their instructions the day before. I used to have a bulge on my right side that would show up in pictures. I am lactose intolerant and gluten as well. Little concerned about this false positive thing though. I will definitely discuss this with my Dr once I get those results. He’s also going to biopsy my small intestine when he does the endoscopy as I do have ibs as well

    1. Hi Susan,

      Sorry about the delayed response. I hope everything went well with your doctor and you were able to plan a treatment and are seeing improvements!

  14. Hi Dr Ruscio. I’m having Hydrogen Breath test and have to stick to their instructions the day before. I used to have a bulge on my right side that would show up in pictures. I am lactose intolerant and gluten as well. Little concerned about this false positive thing though. I will definitely discuss this with my Dr once I get those results. He’s also going to biopsy my small intestine when he does the endoscopy as I do have ibs as well

    1. Hi Susan,

      Sorry about the delayed response. I hope everything went well with your doctor and you were able to plan a treatment and are seeing improvements!

  15. Hello

    I have had major bloating, dull pain just below sternum constant for 4 months. It gets MUCH worse within 30 min of eating….regarless of the type of food. Although I want to eat….I am not due to increased pain…so I have lost 22 pounds in a month. I HAVE MAJOR BLOATING AND GAS AFTER I EAT..SOMETIMES DIAR.All of these symptoms began after taking doxycycline AND AUGMINTINE My GI Doctor has run every test you can imagine.
    CT
    CTA
    2 ENDOSCOPES BIOP FOR EVERYTHING
    GASTRIC EMPTY TEST
    HIDACCK
    HILDA
    DOPPLER ULTRA SOUND
    2 REGULAR ULTRASOUNDS
    2 EKG
    BLOOD WORK
    24 HOUR URINE TEST
    FECAL TESTS
    MRI
    ALL COMPLETELY NORMAL.
    The Dr decided to do a Lactose Breath Test…
    But strongly believed was gallbladdee due to my symptoms although gallbladdee was showing as normal…sced me for surgery on gallbladdee..

    THEN JUST GOT BREATH TESTS JUST CAME BACK AS POSITIVE…BUT ONLY SHOWED POSITIVE VERY LATE IN THE TEST…
    Nurse Pract. WANT TO TREAT ME WITH ANTIBIOTICS WHICH SCARE ME AS ALL MY PROBLEMS STARTED AFTER BEING IN ANTIBIOTICS…I WAS COMPLETELY HEALTHY BEFORE THAT….ACTIVE NO DIGESTIVE ISDUES AT ALL!
    I read and the nurse practitioner Said…as test only showed positive very late…could be FALSE POSITIVE…. Don’t want to take another CRAZY antibiotic….if nit needed…,and not get surgery for gallbladder and that is the real issue…it has been 5 MONTHS OF HORRIBLE CONSTANT BLOATING AND DULL PAIN JUST UNDER STERNUM…..
    ADVICE…Please!!!!!
    Thank You!

    1. Hi Mary,

      I’m so sorry to hear you’re dealing with that, digestive issues can be incredibly frustrating and sometimes difficult to sort out. We can’t give personalized medical advice on the site, but I would recommend that you find a practitioner who is very experienced in treating patients with SIBO, as it takes skill and experience to interpret tests and devise a treatment plan. If you want to avoid antibiotics, you may want to consider the elemental diet. If you want to know how Dr Ruscio treats SIBO, you can listen to this podcast episode: https://drruscio.com/sibo-treatment-protocol-episode-39/

      Lastly, I’d recommend picking up a copy of Dr Ruscio’s book, “Healthy Gut, Healthy You” as he walks through the exact protocol he uses with patients in his clinic to help them overcome a variety of gut issues. You can find it here: https://www.drruscio.com/getgutbook

      Good luck!

  16. Hello

    I have had major bloating, dull pain just below sternum constant for 4 months. It gets MUCH worse within 30 min of eating….regarless of the type of food. Although I want to eat….I am not due to increased pain…so I have lost 22 pounds in a month. I HAVE MAJOR BLOATING AND GAS AFTER I EAT..SOMETIMES DIAR.All of these symptoms began after taking doxycycline AND AUGMINTINE My GI Doctor has run every test you can imagine.
    CT
    CTA
    2 ENDOSCOPES BIOP FOR EVERYTHING
    GASTRIC EMPTY TEST
    HIDACCK
    HILDA
    DOPPLER ULTRA SOUND
    2 REGULAR ULTRASOUNDS
    2 EKG
    BLOOD WORK
    24 HOUR URINE TEST
    FECAL TESTS
    MRI
    ALL COMPLETELY NORMAL.
    The Dr decided to do a Lactose Breath Test…
    But strongly believed was gallbladdee due to my symptoms although gallbladdee was showing as normal…sced me for surgery on gallbladdee..

    THEN JUST GOT BREATH TESTS JUST CAME BACK AS POSITIVE…BUT ONLY SHOWED POSITIVE VERY LATE IN THE TEST…
    Nurse Pract. WANT TO TREAT ME WITH ANTIBIOTICS WHICH SCARE ME AS ALL MY PROBLEMS STARTED AFTER BEING IN ANTIBIOTICS…I WAS COMPLETELY HEALTHY BEFORE THAT….ACTIVE NO DIGESTIVE ISDUES AT ALL!
    I read and the nurse practitioner Said…as test only showed positive very late…could be FALSE POSITIVE…. Don’t want to take another CRAZY antibiotic….if nit needed…,and not get surgery for gallbladder and that is the real issue…it has been 5 MONTHS OF HORRIBLE CONSTANT BLOATING AND DULL PAIN JUST UNDER STERNUM…..
    ADVICE…Please!!!!!
    Thank You!

    1. Hi Mary,

      I’m so sorry to hear you’re dealing with that, digestive issues can be incredibly frustrating and sometimes difficult to sort out. We can’t give personalized medical advice on the site, but I would recommend that you find a practitioner who is very experienced in treating patients with SIBO, as it takes skill and experience to interpret tests and devise a treatment plan. If you want to avoid antibiotics, you may want to consider the elemental diet. If you want to know how Dr Ruscio treats SIBO, you can listen to this podcast episode: https://drruscio.com/sibo-treatment-protocol-episode-39/

      Lastly, I’d recommend picking up a copy of Dr Ruscio’s book, “Healthy Gut, Healthy You” as he walks through the exact protocol he uses with patients in his clinic to help them overcome a variety of gut issues. You can find it here: https://www.drruscio.com/getgutbook

      Good luck!

  17. Hi Dr Ruscio,

    thank you so much for very insightful information…

    I recently did GI Effects (Genova) comprehensive stool test , which has reported overabundance and overgrowth of Firmicutes and Bacteroidetes (total of 3 species of Bacteroidetes and 5 of Firmicutes) . Additionally M smithii overgrowth is also reported. Do you think I should get tested for SIBO ? If so, which test you recommend (glucose/lactulose)

    Thanks in advance

    1. Hi Anu,

      First off, I’d say work with your doctor and go off of their recommendation. If you feel you’re experiencing gut issues, I’d actually recommend getting a copy of Dr Ruscio’s book because he lays out a DIY protocol to hep you overcome frustrating conditions without needing to spend lots of money on testing, etc. You can find it here: https://www.drruscio.com/getgutbook.

      If you do want to get tested for SIBO, both of the tests have pros and cons, but I’d recommend watching the video above where he lays them out and then discussing with your doctor which is the best choice for you.

      Good luck!

  18. Hi Dr Ruscio,

    thank you so much for very insightful information…

    I recently did GI Effects (Genova) comprehensive stool test , which has reported overabundance and overgrowth of Firmicutes and Bacteroidetes (total of 3 species of Bacteroidetes and 5 of Firmicutes) . Additionally M smithii overgrowth is also reported. Do you think I should get tested for SIBO ? If so, which test you recommend (glucose/lactulose)

    Thanks in advance

    1. Hi Anu,

      First off, I’d say work with your doctor and go off of their recommendation. If you feel you’re experiencing gut issues, I’d actually recommend getting a copy of Dr Ruscio’s book because he lays out a DIY protocol to hep you overcome frustrating conditions without needing to spend lots of money on testing, etc. You can find it here: https://www.drruscio.com/getgutbook.

      If you do want to get tested for SIBO, both of the tests have pros and cons, but I’d recommend watching the video above where he lays them out and then discussing with your doctor which is the best choice for you.

      Good luck!

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