The symptoms vary depending on the specific deficiencies. For example, people with a deficiency of the enzyme lactase may experience explosive diarrhea, abdominal bloating, and flatulence after drinking milk. Other symptoms depend on the disorder that is causing the malabsorption. Diagnosis Doctors suspect malabsorption when a person loses weight and has diarrhea and nutritional deficiencies despite eating well. Weight loss alone can have other causes.
Laboratory tests can help confirm the diagnosis.
Tests that directly measure fat in stool samples collected over 3 or 4 days are the most reliable ones for diagnosing malabsorption of fat. A finding of excess fat makes the diagnosis likely. Other laboratory tests can detect malabsorption of other specific substances, such as lactose or vitamin B 12 . Stool samples are examined with the unaided eye and under the microscope. Undigested food fragments may mean that food passes through the intestine too rapidly.