Breath Testing


Breath testing with hydrogen and/or methane breath tests may offer some insight into malabsorption of some FODMAPs. However, the results of these tests are not always definitive, and further investigation is often required to isolate the causes of symptoms. It is important to note that breath testing is of no benefit (and is not recommended) for identifying malabsorption of fructans and GOS - 2 of the FODMAPs commonly found to cause IBS symptoms – because all people malabsorb these (though not all will suffer IBS symptoms).

Given the limitations that can be associated with breath testing for FODMAP intolerances, patients should be referred to a dietitian experienced in gastrointestinal nutrition to be assessed and treated. Dietary trials with an experienced dietitian at Shepherd Works can assist with identifying and managing a range of dietary intolerances while achieving a nutritionally balanced diet. Our philosophy at Shepherd Works is that it is not about finding what you can’t eat – it’s about understanding what you can eat, in the amount that is right for you.


Check out our blog for more info on breath testing

How Do The Tests Work?


The procedure for each test (fructose, lactose, sorbitol and lactulose) is simple. You need to perform each breath test on a different day. When you attend each breath test appointment you will be given a hydrogen breathalyser type device to breathe into. This first sample is recorded, then you will be given a sugar solution to drink, after which another breath sample will be taken from you every 15-20 minutes over the next 2~3 hours. Many people complete the tests for Lactulose, Fructose, Sorbitol and Lactose within 2 hours, although some take around 3 hours. Your referring practitioner will describe which of the test sugars (Fructose, Sorbitol or Lactose – or any combination of these) you are to do. However, a practice test, (a Lactulose test) must be performed prior to any of these test sugars, to make sure you produce enough hydrogen gas. If you are a low- or non-hydrogen producer with Lactulose, you will be changed from the breathalyser device to inflatable bags during the course of your test as these bags allow us to also measure methane gas. This will ensure that we capture whichever type of gas (hydrogen or methane) you produce.

Generally, if you do not absorb the test sugar in your small intestine, then that sugar will continue through to the large bowel. In the large bowel, the sugars are then broken down/fermented by the bacteria that naturally live in the large bowel, and gas is produced. Although some gas is lost out the back passage (as wind/flatus), the majority is absorbed across the walls of the large intestine into the blood stream. In the blood stream, the gas is then carried up to the lungs. The lungs then take up the hydrogen and/or methane gas and it is breathed out. During the breath test conditions, if a rise in gas (hydrogen/methane) levels are detected on the breath after the sugar test, then it may indicate that that sugar is malabsorbed in the small bowel (as hydrogen and methane are not usual gases that are expelled by the lungs in such conditions).

Where Do I Go To Have These Tests?


The breath hydrogen and methane tests are performed at various centres.

To make an appointment with a dietitian click here

Where to next?

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