We usually do three tests which are all based on the same principle. We test for lactose, fructose and sorbate intolerance. In case these sugars are not digested well by the small intestine (due to lack of enzymes and transporter proteins, disorder of intestinal bacteria flora), sugar travels to the large intestine where bacteria starts to break it down resulting in hydrogen being produced.
This way the level of hydrogen increases in the patient’s breathe and can be measured. Testing is done with an empty stomach. We are testing every half hour for three hours after the patient has consumed a liquid containing the specific type of sugar we need to examine.