you were thinking of the breath test for H pylori:
here
Breath test (called the carbon isotope-urea breath test or UBT):
Up to 2 weeks before the test, the patient must stop taking any antibiotics, bismuth-containing medications such as Pepto-Bismol, and proton pump inhibitors (PPIs).
The patient swallows a special substance containing urea (a waste product the body produces as it breaks down protein) that has been made harmlessly radioactive.
If H. pylori are present, the bacteria convert the urea into carbon dioxide, which is detected and recorded in the patient's exhaled breath after 10 minutes.
This test can identify almost all people who have H. pylori and confirm that the H. pylori infection has been fully treated.
this cocmment does not mean in any way that RR is gonna get one....