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Glucose Hydrogen Breath Test for detecting SIBO (results)


Senior Member

has anyone here done this test before? I did it today but we had some problems.

Baseline were 0 ppm, then I drank a glucose drink. After 20 minutes I had 49 ppm. After 40 minutes I measured again but had 0 ppm. After 60 minutes I wanted to test again but the device was broken. The touchscreen didn't work anymore although we tried multiple times to restart it. The doctors' assistant then told me that the device was repaired only one week before because of the same reason.

Now my questions are. Are 49 ppm a positive indicator of SIBO? I heard that even 12 ppm make SIBO likely and 20 ppm prove SIBO.

I wondered why the 40 min value was 0. The causes could be

a) the device was already broken and didn't measure correctly
b) the glucose was already absorbed
c) I don't have SIBO

I heard that glucose gets absorbed very fast and within 60 minutes most tests return to 0 ppm because the glucose is fully gone. Does anyone have experience with glucose breath test results? I have a new appointment for tomorrow, this time they want to take my blood after drinking the glucose. Is this useful?


Senior Member
I did it but with lactulose.

There's no way you can trust whatever numbers you got, then. Better redo the test, preferably with lactulose as glucose gets absorbed too fast. Oh, and be sure the device is looking for both hydrogen and methane.

It's funny that you can never get a simple test done just by going to a doctor. It seems that you always have to take care for it by yourself by choosing only specialists who know how to do certain tests the right way.

I just read this:


"Hydrogen breath testing with lactulose may be able to diagnose only 60% of patients with SIBO, and glucose may be only slightly better."


Senior Member
Indeed lactulose is much better. Glucose is useless for SIBO further down the small intestine. Can only detect it at the start of the small intestine.

I had a silly doctor do this to me before I knew better. Consequently I suffered another 1 1/2 years thinking I didn't have SIBO before a doctor with half a brain ordered a lactulose test and H2S urine test. A flat line the whole way through a lactulose test means you're either producing H2S or pretty much sterile (unlikely).