Diagnosing SIBO: Breath Testing Basics

Hi friends!

I wanted to write a post on the basics surrounding the breath tests for diagnosing SIBO. Because the information out there is not so basic, or easy to understand, and there is a lot of conflicting information, I will do my best to try and ease your suffering!

This post will cover the two main types of breath tests, their differences, where you can purchase breath test kits online, breath test preparation diet, procedure, and finally as a bonus, my before-and-after results!

In case you aren’t yet familiar with my story, I was diagnosed with SIBO in August 2018. Before being diagnosed, I suffered from the common symptoms associated with SIBO, such as bloating, nausea, indigestion, fatigue, low energy and constipation (which got much much worse after the Elemental Diet).

I would like to walk you through the process of diagnosing SIBO, so that you are familiar with the best methods, as well as feel more at ease going through the steps yourself! I know this information can be conflicting and overwhelming, so I will do my best to help you understand it, and have a clear picture of the data all in one place!

Best Ways to Diagnose SIBO

Right now, the best way to diagnose SIBO is through a breath test. There are two main types of breath tests available for diagnosing SIBO: Lactulose and Glucose breath tests.

There is also a new test called the IBS-Smart, a blood test, which can help diagnose SIBO or other IBS-type symptoms, caused by food poisoning (also known as post-infectious IBS).

Another option is to do a GI-Map test.The GI Microbial Assay Plus (or GI-MAP™) test is a DNA-based stool test that provides a detailed analysis of your individual gut microbiome. It provides an accurate analysis of pathogens including bacteria, toxins, parasites and viruses, and how they contribute to perturbations in the GI flora and relate to many inflammatory, autoimmune, metabolic, cardiovascular, and other chronic diseases.

The benefits of the GI-Map test are that they will tell you exactly which strains of “bad” bacteria or pathogens are present. This will allow for an individualized treatment plan, and could help explain some of the symptoms you are experiencing.

Results sample from a GI-Map test

There are various other tests available that can help you understand your symptoms and put you on the best treatment plan. More information can be found here, with detailed descriptions of each option.

What is a Breath Test?

Breath testing is a non-invasive test that is used fairly frequently as a way to diagnose or rule out SIBO. The test works by testing for the presence of hydrogen or methane in the breath at specific intervals, after a person drinks a liquid containing a sugar solution, such as glucose or lactulose.

The hydrogen produced by the bacteria is absorbed through the wall of the small or large intestine or both. The hydrogen-containing blood travels to the lungs where the hydrogen is released and exhaled in the breath where it can be measured.

The presence of hydrogen in the breath prior to the 90-minute mark is thought to indicate that bacteria are present in the small intestine as they are interacting with the consumed sugar and releasing hydrogen or methane, which is then excreted through the breath. This cut-off time period is based on the fact that it typically takes two hours for an ingested sugar to reach the gut bacteria that are present within the large intestine, which is where such colonies are supposed to be.

What is the Difference Between the Lactulose and Glucose Breath Tests?

The main difference between the two tests appears to be both the solution that is consumed (lactulose and glucose are both sugars but different types) as well as the validity each provides.

Lactulose is a simple disaccharide. Generally, there is no lactulase enzyme in the small intestine to hydrolyze this sugar, therefore it is transported intact to the colon where it is metabolized by colonic bacteria. End products of its metabolism include H2 and CH4.
Glucose is straight away absorbed in the small intestine. However, if there is bacterial overgrowth in the small intestine, bacterial fermentation of glucose leading to production of H2 can take place prior to the absorption of glucose, which is measured by increase in H2/CH4 conc0entration.

There is some research that shows that the Lactulose breath test (LBT) is more likely to find SIBO, but also comes with a higher false positive rate (meaning the person comes back positive on the lab test but they don’t actually have SIBO), than the glucose breath test (GBT).

Based on many studies, in summary, it appears the LBT seems to be over reporting positive results for SIBO.

Also, according to another study, the diagnostic accuracy of glucose was found to be 72%. The diagnostic accuracy of lactulose was found to be 55%.

What Constitutes a Positive Test Result?

You might be wondering how to interpret your breath test once you receive the results. No worries! It isn’t difficult once you have the information you need to understand how to read the test 🙂

Here is an example from Genova Diagnostics that shows a positive Hydrogen (H2), negative Methane (CH4) reading:

Here is an example from Genova Diagnostics that shows a positive Methane (CH4) and negative Hydrogen (H2) reading

Unfortunately there seems to be no consensus in the SIBO community on the exact increase amount that determines a positive reading on a breath test. However, the data that exists currently according to different sources, are quite similar, so at least there’s that!

Take a look below to see what different sources are saying:

According to NCBI

Glucose (GBT): Any increase ≥ 10 ppm in H2/CH4 concentration in two consecutive readings above the basal value is to be considered as significant and indicates about SIBO.

Lactulose (LBT): The time interval between ingestion of lactulose and rise in breath H2/CH4 concentration ≥ 10 ppm in two consecutive readings above the basal value is measure of orocecal transit time.

According to SIBO Center
SIBO may be suspected for increases ≥ 20 PPM for H2, ≥ 12 PPM for CH4.

According to Genova Diagnostics
A rise of H2 of ≥20 ppm over baseline in the first 90 minutes of testing is positive for SIBO.
A peak methane level > 10 ppm at any point is indicative of a methane-positive result

These are general guidelines and unfortunately they are not concrete at this time. There are also a few assumptions being made that may make your diagnosis incorrect:

One of the biggest assumptions being made that leaves room for error is the following. If we are going based on Dr. Pimental’s (a doctor considered an expert on SIBO) criterion for a positive SIBO breath test, which is a rise in breath hydrogen 20 ppm above basal levels within 90 minutes after ingestion of lactulose, it is presuming that mouth-to-cecum transit time is always greater than 90 minutes. It is assuming that a peak in breath hydrogen within 90 minutes after lactulose ingestion must be due to bacterial fermentation in the small bowel.

However, this assumption is not necessarily correct. According to several studies, mouth-to-cecum transit time in Asian populations is often shorter than 90 minutes. In one study, median mouth-to-cecum transit time in 12 healthy Indian subjects was 65 minutes (range 40 to 110 minutes). In a study of 45 healthy Taiwanese, mean mouth-to-cecum transit time was 85 minutes.

Therefore, a large proportion of these healthy subjects would have been falsely diagnosed as having SIBO if Pimentel’s criterion had been employed.

According to Dr. Ruscio (another doctor who is considered a SIBO expert) says that its not that lactulose cannot or should not be used, but that we need to consider these factors before making a diagnosis.

Dr. Ruscio also makes an interesting point, when asked why we should have any faith in a lactulose breath test:

“Let’s assume for a moment we have a negative lactulose breath test. If it’s negative, we’re not going to have a rise of parts per million of hydrogen or methane in the small intestine. We all can agree to that. What if at test tubes eight, nine, and ten, where we know for sure we’re in the colon, we don’t get a rise? So that then can tell me, hold on here. We could have a false negative with lactulose. So lactulose can give us some very good data”.

Overall, lactulose testing appears to have a higher false positive rate, meanwhile glucose testing can underestimate SIBO, but is unlikely to overestimate SIBO.

If I may add some of my own thoughts on the subject: Use your symptoms and the test results as a guide!
Something interesting happened to me when I went to do my second lactulose breath test, after my SIBO treatment. I had all of the same symptoms, literally not a single one improved after treatment, if anything I felt worse (I discuss some of that in my elemental diet post) !

But miraculously, the lactulose breath test came back negative (I only had a rise after the 120 minute mark). If my doctor was going based on my test results alone, I would have been sent home with no further action. This would have been very unhelpful seeing as I was still unwell.

Yes, the test results were negative, but I evidently still needed to do a lot of work and healing. Luckily, after switching to Paleo AIP, and getting on the right supplements, I was able to reduce a lot of my remaining (not quite all) symptoms.

When I speak with people about whether or not they should re-test after their treatment, even though they still feel the same, or with little improvement, I always tell them it’s important to re-test, because data is valuable: did your treatment work, and how much did it affect your numbers?

Your second set of test results will help tell you which direction you should go in, after your first set of treatment. If I had gone simply based on symptoms, I probably would have done another round of herbals (completely unnecessarily)! Remember that herbals also kill off the beneficial (“good”) bacteria, along with the overgrown or misplaced (“bad”) bacteria.

I would have also not known that I had successfully cleared SIBO, and that something else was needing my attention (in my case it was a leaky gut, and needing a diet overhaul!). Not to mention the sadness and frustration that we would go through, thinking our treatment didn’t do a damn thing, when in reality, at least in my case, it did just the trick!

On that note, also make sure your doctor gives you your test results! I see far too many people not receiving their test results, but rather their doctors simply telling them “Nope, not SIBO”, or worse “You have SIBO” but not give you any indication as to what kind (hydrogen-dominant or methane-dominant), nor the numbers you got from doing the test.

This is important to know for two reasons:
1 – Knowing which type of SIBO you have will help you choose which herbals or antibiotics to take (for example, allicin is great for methane-dominant SIBO, not so much for hydrogen-dominant SIBO)

2 – When you do your re-test, you can actually compare the data from the second test to the first. This will tell you whether what you’ve been doing to treat SIBO is actually working or not

Where to Order Breath Tests Online

If you are unable to have access to a naturopath, doctor, have trouble receiving a referral for a breath test, or you simply want the convenience of doing the breath test in the comfort of your home, there are online breath test kits available!

I provided a list that sells breath test kits from the U.S, Canada and UK.

Breath Test Preparation

The first step is ensuring your test checks for both methane and hydrogen! I see a lot of people are going through the expense and time that it takes to do a breath test, only to find that their doctor only checked for hydrogen. You absolutely need to be checking for both types of gasses.

Once you have ordered your breath test, or have received a referral to do a breath test at a laboratory, you will (hopefully) receive instructions on how to prepare for the test.

The instructions should include both medications to stop, avoid, as well as which ones do not affect the test results. You should also have instructions for the prep-diet.

The instructions might slightly vary depending on the company or lab you are doing your test with, but they will look something like this (always double-check with your lab or company for specifics):

Reference for the below excerpt
“One month before:
Do not use any colon cleansing products (such as that used prior to a colonoscopy).
Four weeks before: Do not take any antibiotics or probiotics.
One week before: Do not use any laxatives, fiber supplements, or stool softeners.
48 hours before: Avoid high carbohydrate meals and snacks, particularly whole grain bread or pasta. You can eat broiled fish or chicken, white bread or rice, potatoes, coffee, and tea. If you are taking a medication for GERD, discuss whether or not you should continue to take the medicine in the days leading up to the test. Typically, it is recommended that you discontinue the use of any prokinetic medications, but that you can continue with a PPI medication.
12 hours before: Do not eat or drink anything. This includes gum and candy. If you are a smoker, do not smoke. Do not exercise, as exercise can throw off test results.”

Here is what I personally received from the laboratory I did my test with

As you can see, my Lab’s instructions are slightly different than what you might find with a quick google search. That’s why its best to just follow the lab/company instructions.

My lab  also did not mention whether or not to brush your teeth before the test. I did however rinse my mouth with mouthwash before consuming the lactulose, as per their instructions.

There is conflicting information as to whether or not this impacts the results of the test. Multiple sources I read did not seem to follow the same procedure either, when it comes to teeth brushing the day of the test.

However, based on some studies, it seems that brushing teeth before the exam is best, as the oral bacteria (yes, we have a microbiome in our mouths, too!) can interfere with the sugars consumed before the test, thus possibly giving incorrect data in the results.

Again, if you aren’t sure, contact your lab or breath test company for clarification, as not following their instructions might end up with false test results or them even sending you home for not following the instructions!

Breath Test Procedure

The lactulose breath test is a 3-hour long test. If you are doing it at home by yourself, the kit should come with very precise instructions on how to properly perform the test and collect the samples.

If you are going into a lab to do the test, there will be a technician who will be helping you collect each sample.

You should start the test off with blowing into a bag, before consuming the sugar (lactulose or glucose). This will be your baseline amount (the amount of hydrogen and/or methane gas you measure without the sugar).

Next, they’ll have you drink a small amount of the lactulose or glucose.You’ll then breath into a bag every 15 to 20 minutes as your body digests the sugar.
Note: You may experience diarrhea or upset stomach after consuming the lactulose solution.

The sample collection is on every 15 minute intervals, for 2 to 4 hours. Mine was 3 hours long because it was a lactulose test. Glucose is usually stopped after 135 minutes because the sugar is quicker absorbed compared to lactulose.

My Breath Test Results

In case you guys are curious, or just want proof/hope that SIBO can be cured, take a look below!

My first lactulose breath test happened on July 31st 2018. As you can see below, I had a positive reading for both methane (CH4) and hydrogen (H2) with very high numbers – hydrogen hit 130 at the 90 minute mark! Methane hit 39 at the 90 minute mark – in both (I hit the SIBO jackpot *eye roll*!).

Hydrogen (H2) results. Baseline (0 minutes) was 73, surpassing the 20ppm increase at the 60 minute mark (an increase of 39ppm, indicating a positive H2 reading)

Methane (CH4) results. Baseline (0 minutes) 26, surpassing the 10ppm increase at the 75 minute mark (an increase of 13ppm, indicating a positive CH4 reading)

My subsequent lactulose breath test happened on May 15th, 2019 (about 9 months after treatment/lifestyle changes). As you can see below, I had a negative reading for both Hydrogen and Methane – woohoo!

I will note that the rise occurred after the 120 minute mark, which is generally a normal outcome. The rise after the 120 minutes are usually the result of normal bacterial fermentation in the colon.

There is always the possibility that the transit time was slow due to slow motility, and that is something I was experiencing, symptom-wise. At this time, I still struggled with some degree of constipation, as well as food sitting in my stomach, undigested for quite some time after consuming a meal.

I decided not to continue with herbals because I felt comfortable with the decision that it wasn’t SIBO, but rather another issue I needed to work on to avoid a SIBO relapse. Luckily, as previously mentioned, going on Paleo AIP, and going on the right supplements (Ox Bile especially) really helped with those symptoms!

Hydrogen (H2) results, post treatment

Methane (CH4) results, post treatment

So there you have it, folks! It is possible to heal from SIBO, and its even possible to not relapse – I am SIBO-free for almost a year, now!

I do receive quite a few questions regarding how I managed to clear SIBO, and I would love to share that with you guys, so stay tuned for my next blog post on how I did it!

I hope you found the above information helpful. If you did (or even if you didn’t), I would love to hear from you! Leave a comment below, and I will respond with any comments or questions you may have 🙂

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