SIBO Breath Test

SIBO Breath Testing: The Best SIBO Test to Diagnose Bacterial Overgrowth 

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 SIBO breath testing as well as other tests that doctors use and what you need to know about testing for SIBO so that you can get the best results. Testing is super important because it determines the treatment approach you take based on your gas levels.

*Patients with SIBO-IBS type symptoms need to remember that doing numerous colonoscopies or endoscopies is a waste of time and money. It is important to rule out structural and other issues that can be seen with the human eye by scoping the bowels but it does not make sense to continue to test with invasive procedures because bacteria cannot be seen with the eye.


 Tests Available for SIBO

There are a few ways that doctors can test for SIBO-IBS. While none are perfect methods they can give you good data to proceed with treatment options. Below are the main tests for SIBO:

  1. Hydrogen & Methane Breath Test (Standard testing method to diagnose SIBO)
  2. Culture
  3. IBS Blood Test

SIBO Hydrogen Breath Testing: How it Works

Breath testing is the best option available right now and is used by most practitioners. The hydrogen breath test is used to measure the amounts of hydrogen and methane in your breath after feeding the bacteria in your small intestine with a sugar solution called lactulose. Unfortunately, the test cannot currently measure the third gas hydrogen sulfide quite yet. Hydrogen and methane gases are only produced by bacteria and not humans so we can measure the amount of gas produced 2-3 hours after ingesting sugars by breathing into tubes.

*In order to get an accurate test result patients need follow a low fermentation diet 1-2 days before and fast for 12 hours before the test. This ensures that you don’t have excess fermentation before the test.

On the day of the test you first take an initial breath sample to get a baseline measurement. Then you drink a dose of lactulose or glucose sugar to feed the bacteria in the small bowel. Every 20 minutes you will continue to exhale into small containers. To do this all you do is use a small straw which you use to breath into the glass tube. You do this for a total time of 2-3 hours.

*The reason it takes so long is because you have to allow for the full small intestine transit time and give the bacteria throughout the small bowel a chance to eat the sugar and produce gas.

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)

*All SIBO breath tests should use lactulose to evaluate the gases throughout the whole length of the small intestine. 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.


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 specific patterns like elevated levels of hydrogen or methane during that time period.

There are certain patterns that are representative of SIBO that show on the testing graph. Although, interpreting the results can also be tricky for some people because there are certain bugs like Hydrogen Sulfide producers which a small portion of patients with SIBO have that are harder to detect and produce abnormal test results where the line is flat instead of peaking.

Below are the 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

To learn more about the scientific research on interpreting breath tests check out this article.


Important Points to Note With SIBO Breath Testing

  • 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 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.

**Order your 3 hour lactulose test here**


Culture to Test for SIBO

This testing method to evaluate SIBO is not very common. It is more invasive and requires that the patient is in a hospital setting where they would be getting an endoscopy done. If a patient is getting an endoscopy done which is when a doctor uses an endoscope or tube that goes down through your mouth and into the intestines to scope them you can request a culture of the small intestinal fluid. The doctor would then culture the fluid from your small intestine to see what bacteria grows. You would then be able to determine if you have SIBO.

*If you need to have an endoscopy done you can talk to your doctor about a culture to test for SIBO


IBS Blood Test

The last test that doctors can use to diagnose SIBO or post-infectious IBS is with the IBS Chek blood test. This was developed by Dr. Mark Pimentel. This test is a simple blood test that tests for anti-CdtB and anti-vinculin. Research has found that a percentage of patients with SIBO had a previous episode of gastroenteritis which has been found to be a cause of nerve damage which leads to SIBO.

Although this test can determine if you have SIBO-IBS with diarrhea from food poisoning and give you a diagnosis you would likely still need to use the hydrogen breath test to measure the gas levels for your treatment protocol. Below are blood tests that can measure anti-CdtB and anti-vinculin: