Give adults 25 g D-xylose in 250 mL water. Encourage the patient to drink an additional 250 mL water following the xylose dose. The patient may have water as desired, but no other food or fluids. Smoking should be prohibited. The patient should rest in a chair or on a bed until completion of test.
Mild diarrhea is common following xylose ingestion.
Collect the second serum sample 2 hours after giving the xylose dose. Separate serum from clot promptly. After giving the xylose dose, collect all urine for the next 5 hours. Record the xylose dose given and the total volume of the 5-hour urine on the test request form. Send and label the fasting and 2-hour serum samples.