- Examination of stool to detect the presence of blood, abnormally increased levels of fat (steatorrhea), or the presence of Giardia lamblia.
- A lactose tolerance test
, during which patients are provided with a test
dose of lactose by mouth. After receiving the test dose, those with lactose intolerance may soon develop abdominal discomfort, diarrhea, and excessive flatulence. Breath or blood samples are obtained during the test to confirm the presence of lactose intolerance.