Breath testing for lactose, sucrose, fructose and other substances can be used in the diagnosis of a variety of conditions such as lactose intolerance, fructose intolerance, bacterial overgrowth syndrome and more. In people who are unable to digest the sugar found in milk (known as lactose), this condition can be determined by having the patient consume a beverage with a large amount of lactose and then analyzing their breath at certain intervals to see if there are high levels of hydrogen. When this is the case, the patient may be determined to be lactose intolerant. In patients who have a problem absorbing fructose (the sugar that occurs in wheat and some fruits and vegetables), this condition can be diagnosed by comparing an analysis of the patient’s breath before consuming something with fructose and over the three hours following consumption. The test to detect sucrose intolerance is a C13 sucrose breath test – and also evaluates the amount of hydrogen within a person’s breath.