Diagnosis of SIBO

FixSIBO OP Dr James Freeman profile photo

Diagnosis of SIBO

Medically reviewed by:
Dr James Freeman

Diagnosis of SIBO is challenging and not widely performed. A combination of symptomatic review and breath testing is clinically considered the best option.

Invasive methods comprise culture-dependant and culture-independent approaches requiring a fluid sample from your small intestine.

Let’s explore some potential tests commonly performed for IBS.


Colonoscopies and endoscopies, more often than not, turn up nothing. That is because they don’t go to the place we need to see. They are expensive and come with risks, so they should not be the first protocol used to diagnose SIBO.

Routine testing for parasites

Parasites are not the cause of SIBO, so this will tend to test negative unless you have this separate condition
co-existing with SIBO.

Stool samples

Patients with leaky gut type SIBO may have an elevated zonulin level in their stool (however, the literature shows this is not always the case, and this may not be a reliable diagnostic tool), and they also may have elevated fecal secretory IgA, an inflammation marker. However, these tests are not commonly performed.

Breath testing

Lactulose breath testing is currently the best available option for diagnosing SIBO. It can be an effective way to figure out if someone may potentially have SIBO and the subtypes medicine is currently aware of.

Breath testing is not as widely available as other standardised tests so sometimes it is easier for people to do a process of elimination and symptom based assessment if they live in an area or don’t have the economic means to purchase the testing.

Continued testing throughout your treatment if you have a positive reading can help you assess the effectiveness of your treatment protocol. However, this is simply not affordable for many people.

How breath testing works

Breath testing works by establishing a baseline breath and then having the patient drink a solution the body can’t absorb. If you have enough overgrowth in your small intestine, they will ferment this non-digestible sugar and produce hydrogen or methane, depending on what type of bacteria you have. You can also produce both during the test.

Because testing for SIBO can be so challenging, many patients choose to do a process of elimination. This can quickly be done by having your doctor run routine tests for parasites, active infection, celiac disease, and lactose intolerance to make sure none of these common IBS causes is your underlying problem.

If all these come back negative, yet your symptoms are persistent and fit the description for SIBO, undergoing treatment to see if it resolves your issues may be worth considering. However, if you consider this option, we can’t emphasize enough how important ruling out other causes is.

Treatment can be in the form of antibiotics or antimicrobials, and the scientific literature suggests supplementation is also a very integral part of a full recovery and preventing relapse.

We will discuss both options in detail, based on the experience of many patients in the SIBO community. Neither is wrong or right, and it is all about personal preference.