Treating SIBO (Part 5): Breath Tests - Hollywood Homestead

It isn’t just stomach acid which breaks down food in your gut.  You also have armies of bacteria in your gut which feed off of undigested carbohydrates (like sugars and fiber).  When the bacteria eat the carbs, they produce gases as a byproduct.  Before you get scared about the idea of bacteria in your gut, you need to know that it is normal and even healthy to have certain amounts of some types of bacteria in your body.  The problem occurs when you have too much or the wrong type of bacteria in your gut — such as is the gas with SIBO (Small Intestinal Bacterial Overgrowth syndrome).

There are many ways to diagnose SIBO (which we talked about in the last part of this series).  However, there are a lot of limitations with many of these diagnosis methods.  The best way to diagnose SIBO is with breath tests. These tests measure the amounts of certain gases in your gut.  If the levels are high, then it indicates that bacteria levels are too high.


This is part of a series on Treating SIBO.  If you missed the last parts of the series, check them out here:


What Are Breath Tests Used For?

The bacteria in our guts feed off of carbohydrates. They produce gases as a byproduct. Some of the gases are then absorbed through the lining of the colon and get into our blood. From there, the gases make it to our lungs and are exhaled in our breath.

Breath tests aren’t just used to diagnose SIBO.  They can also be used to diagnose H. pylori, lactose intolerance, and fructose intolerance.  However, it is important to note that the breath tests are slightly different for each of these conditions.  For example, the bacteria H. pylori produces carbon dioxide, so this is the gas that labs will be looking for in the breath test samples.1 (Read about how to treat H. pylori naturally here)

To diagnose SIBO with breath tests, labs need to look for elevated levels of hydrogen and/or methane.  Note that there is a difference between Hydrogen SIBO and Methane SIBO, which we will address later in the series.


How SIBO Breath Tests Are Performed

You can order SIBO breath tests to take at home, or you can perform them at the lab. You will be required to fast for at least 12 hours before the test is taken. That means no food, but prescription meds and water are okay. You will also have to follow a special diet for 1-2 days before the test. The diet basically removes any fermentable foods so you don’t have gas in your GI tract prior to the test and get a false positive.

To take the test, you first breath into a little tube (pictured below) to measure your base hydrogen and methane levels. Then you drink a special solution of lactulose or glucose. You breathe into the tubes again every 20 minutes.   To do it, you just breathe into them through a cocktail straw for a few seconds.  You will see the condensation form.  Then put the lid on and restart your timer.  The test measures how the levels of hydrogen and methane change.   A positive SIBO breath test is defined as one where there are peaks of hydrogen and/or methane after taking the sugar solution.2


sibo breath test tubes
These are the suckers I had to breath in every 20 minutes for the SIBO breath test


You Must Test for Both Hydrogen and Methane

If your doctor tells you to get a test for just hydrogen, you should insist on testing for methane (and also consider switching specialists!).   The bacteria in your gut feed off of carbohydrates and produce hydrogen as a byproduct. However, 8-27% of people do not have detectable levels of hydrogen production in their guts from bacteria. Instead, they produce methane.   This is because our guts also contain archaea, which are similar to bacteria but in a different kingdom of organisms. Archaea feed off of hydrogen and produce methane gas as a byproduct. So, a bacterial overgrowth could cause increases in hydrogen, methane, or both. We will get into this more in the next section of the series about the difference between Hydrogen and Methane SIBO.

Further, certain types of bacteria in the gut produce methane instead of hydrogen. Some of these include: Staphylococcus aureus,Streptococcus viridans, Enterococci, Serratia and Pseudomonas species. If you were to test just for hydrogen, you could miss overgrowths of these bacteria and get a false negative.3

Here is what my breath test looked like. You can see that methane levels are elevated – which is why it is so important to test for both hydrogen and methane:

hydrogen methane breath test
Here is what my breath test looked like. You can see that methane levels are elevated – which is why it is so important to test for both hydrogen and methane


Lactulose vs. Glucose SIBO Breath Tests

Both lactulose and glucose are types of sugars. Not sugar as in the white stuff you buy in supermarkets, but sugar as in the substance that our bodies break carbohydrates down into.  Bacteria digest the sugars and produce gas as a byproduct, which can be measured in a breath test.

There are also other breath tests available, such as one using the sugar xylose, but these aren’t as reliable and may give a false negative.

Glucose Tests: Both humans and bacteria absorb glucose. We humans absorb it in the first three feet of the small intestine. If the glucose breath test shows that gas levels rise, it means that SIBO is present in the first part of the small intestine.  It doesn’t tell us anything about whether SIBO is present in the end of the small intestine.

  • Are considered more accurate
  • But won’t diagnose SIBO in the end of the small intestine (which is where it is more common).

Lactulose Tests: Humans don’t absorb or digest lactulose — only bacteria in our bodies will do that and will produce gas as a result.  The test isn’t as accurate as glucose tests, but they can detect SIBO in the end of the small intestine, which is where it is considered more common.

  • Not as accurate as glucose tests
  • But will diagnose SIBO in the end of the small intestine.


3-Hour Lactulose Test is the Gold Standard

The 3-Hour Lactulose breath test is considered the Gold Standard for diagnosing SIBO. Unfortunately, most laboratories only offer shorter tests.  These shorter tests aren’t as reliable because it takes time for hydrogen and methane to travel through the gastrointestinal tract, into the blood, and out the lungs into our breath.4  

The bottom line? Choose a lab test with a longer time.



Good news! There are now SIBO breath tests that you can order directly without a doctor’s order! While I’m a HUGE fan of having a doctor’s guidance, I understand the need to know whether you have SIBO or not before you invest in a practitioner.

You can order the test directly and it will be sent to your home with instructions on how to take it and how to send it back and get your results!


Next up in the series: The difference between hydrogen and methane SIBO


Ready to eliminate SIBO once and for all? Get your copy of The SIBO Solution: Your Comprehensive Guide to Eliminating Small Intestinal Bacterial Overgrowth by clicking HERE. You’ll also receive a BONUS SIBO Detox Support Guide mini ebook with your purchase.

Treating SIBO (Part 5): Breath Tests - Hollywood Homestead

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Sylvie McCracken is a former celebrity assistant in Hollywood turned full time entrepreneur currently living in Ashland, Oregon with her kids. She writes about treating and preventing health conditions with real food and natural remedies, as well as anything else she feels like writing about because she's a rebel like that. 😉 he also mentors health professionals turned entrepreneurs on her other site,