SIBO testing continues to be a hotly debated subject because it is challenging to get a 100% accurate picture of the bacteria in the small bowel. This is because the small intestine is hard to reach. To see or sample the small intestine a colonoscopy only reaches the end portion of the bowel and an endoscopy only reaches the top part. The small intestine is estimated to be around 20 feet long so there is a large part in the middle that we can’t reach easily.
In this guide I will walk you through everything you need to know about breath testing and how it can be used to diagnose SIBO. Testing is important because it determines the treatment approach you take based on your gas levels.
Everyone has bacteria in their guts. These bacteria ferment carbohydrates and produce gas as a byproduct. In a normal healthy gut there is more bacteria and fermentation in the large intestine. The small intestine is supposed to have smaller amounts of bacteria and its main function is the digestion and absorption of essential nutrients. A breath test for SIBO is used to measure the amounts and kinds of gases produced in the small bowel. When there is bacterial overgrowth there is excessive gas produced in the small intestine. This is what the test measures.
So, how is the breath test able to capture these gases?
When conducting a breath test you ingest a sugar solution to feed the bacteria in your gut. The microbes in your gut then ferment that sugar solution and produce gas. This gas is then absorbed through the gut lining, then into our blood, then transported to our lungs where we exhale it in our breath. We then capture this breath sample in the test tube and can analyze the types of gases which were produced during the 3 hour test period.
How Do You Conduct a SIBO Breath Test?
Breath tests can be ordered by your doctor and conducted in the office or you can take the test in the comfort of your own home. The medical company will simply ship the kit which includes your sugar solution and test tubes to your home.
In order to get accurate test results you MUST follow a specific testing process.
SIBO Test Prep Process:
Order your kit online which is shipped to your house
Follow a low-fermentation diet for 1-2 prior to test day
Fast for 12 hours the evening before your test in the morning
Test Day Process:
Grab a timer and book to have for the 3 hour testing period
Before drinking lactulose, take a baseline breath sample a few minutes before the hour (7:57)
Drink your dose of lactulose or glucose to start feeding bacteria
Every 20 minutes for the duration of your test breathe into the small test tubes
After taking a breath sample seal each tube and restart your timer
When finished, put your tubes back in the box and mail to lab
It’s important that you follow the breath test preparation guidelines by eating a low-fermentation diet and fasting for 12 hours. If you do not do this it can cause a false test result. The reason doctors instruct you to follow these guidelines is because you want to start the test with a normal baseline of fermentation. If you go into the test eating broccoli and cauliflower that will naturally elevate your gas levels making it difficult to gauge your true gas levels.
The video below explains the test in more detail:
Lactulose vs Glucose SIBO Breath Tests
Lactulose and Glucose are two different types of sugars that our bodies break carbohydrates down into. Bacteria digest these sugars and make gases as a byproduct which can then be measured in a breath test.
So, what’s the difference between the 2 types of sugars used for testing?
Lactulose Tests: Lactulose is a sugar that humans cannot digest, only bacteria can. Lactulose does not get absorbed and reaches the end of the small intestine which is where SIBO is thought to be more common. This allows us to get a picture of the whole small intestine.
Lactulose will diagnose SIBO in the end of the small intestine
Standard form of breath testing
Glucose Tests: Glucose is a sugar that is absorbed by humans and bacteria. Glucose is absorbed higher up in the small intestine (first 3 feet) which shows us if SIBO is present in the upper part of the small intestine. Unfortunately, this test does not show us if SIBO is present in the end of the small intestine since it is absorbed so quickly.
Doesn’t diagnose SIBO in the end of the small intestine (which is where it is thought to be most common)
The gold standard for SIBO breath testing is the 3 hour hydrogen and methane lactulose test.
There is a benefit if you are willing to do both glucose and lactulose breath tests because you will be able to tell with the glucose test how high up the bacteria are but you should always do the lactulose test to measure the whole length of the small intestine.
Interpreting SIBO Breath Test Results
Interpreting SIBO breath test results can be tricky. Doctors basically check your levels of hydrogen and methane throughout the 2 hour test and look for elevated levels of hydrogen or methane during the 2 hour small intestine transit time.
It’s important to note that you must test for both hydrogen and methane. This is because methane producing bugs (methanogens) consume hydrogen gas to produce methane. If you just tested for hydrogen you could miss a positive SIBO diagnosis because the test could show low levels of hydrogen when in reality the methane bugs are eating that hydrogen to produce methane gas.
There is also a third gas called hydrogen sulfide which a portion of SIBO patients produce. Currently, we do not have the technology to detect this gas but it can be problematic as well. This is when things can get more complicated, but the hydrogen sulfide producing bugs also consume the other gases to produce h2s. Often times, people with excessive hydrogen sulfide gas will show a flat line graph. Don’t worry, your doctor should be able to interpret this for you!
Below are the typical positive and negative test results.
Typical positive SIBO breath test results:
Hydrogen or methane is >20 ppm up to 120 minutes after ingesting the solution
Hydrogen or methane is elevated at baseline >20 ppm
Negative SIBO breath test results would typically be:
Hydrogen or methane is <20 ppm up to 120 minutes after ingesting solution
Usually hydrogen or methane stays below 20 ppm up to 120 minutes until it reaches the large intestine spike
In the test graphs below, you can get a picture of what a negative and positive result looks like. The charts on the left-hand side are negative and the charts on the right-hand side are positive.
You must follow a SIBO breath test prep diet for 1-2 days prior and fast for 12 hours before testing
You can do the breath test with a take home kit and mail it in to be evaluated or take in your doctors office
If your test shows high gas levels this may indicate a longer treatment period to reduce them
You and your doctor need to see the whole breath test graph to interpret it correctly
The breath testing machine must be calibrated and test for methane
Re-testing is very important after doing any SIBO treatment to see how much the gas levels have decreased
Where Can You Get a SIBO Breath Test?
Great news! There are now SIBO breath tests that you can order directly to your home without a prescription. While it’s important to seek the care of a great doctor, I understand the need to find out if you’re dealing with SIBO before investing your valuable time and money in a practitioner.