Xylose Tolerance Test (Fasting, One-, Two-, Three-, Four-, and Five-hour Blood + Five-hour Urine)

Diagnose intestinal malabsorption syndromes.

This test was developed, and its performance characteristics determined, by LabCorp. It has not been cleared or approved by the Food and Drug Administration.

May cause mild diarrhea.

Patient must fast a minimum of eight hours prior to administration of d-xylose (LabCorp N° 26599, containing 25 g d-xylose). Pediatric patients (younger than nine years of age) should fast only four hours. No restriction on water. Weigh patient for proper dosage of d-xylose. Patient must remain in supine position for duration of the test except during urine collection. Patient should refrain from foods rich in pentose (fruits, preserves, and grains) for a 24-hour period prior to the test. Weight-based dosage of d-xylose for oral administration: 0.5 g/kg body weight up to a maximum of 25 g. Dissolved in water 10% (w/v) with a maximum of 250 mL. Patient should drink eight ounces (250 mL) of water after d-xylose administration and another eight ounces after one hour. Record total five-hour urine volume and send aliquot. Record total on the test request form.