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D-Xylose Absorption Test

Results continued...


D-xylose in urine (5-hour urine sample)1


16%–33% of the D-xylose dose is found in the sample.


More than 16% of the D-xylose dose or more than 4 grams (g) is found in the sample.

Adults age 65 and older:

More than 14% of the D-xylose dose or more than 3.5 g is found in the sample.

Low values

Low values may be caused by:

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Vomiting after taking the D-xylose solution.
  • Being dehydrated before starting the test.
  • Eating foods high in pentose within 24 hours before the test. These foods include fruits, jams, jellies, and pastries.
  • Large amounts of bacteria in the intestines.
  • Kidney disease or bladder problems that prevent you from completely emptying your bladder.
  • Medicines, such as antibiotics, aspirin, and heart medicines. Many medicines can affect D-xylose test results.
  • Physical activity during the test. You will be instructed to rest quietly until the test is complete.
  • Conditions that cause food to remain in the stomach for a long time.

What To Think About

  • If you have an abnormally high amount of bacteria in your intestines, you may have to take antibiotics for a day or two before the test.
  • This test can cause dehydration. Make sure that you drink enough fluids to replace lost liquids after you have completed the test. Tell your doctor if you have problems with diarrhea after drinking the D-xylose solution.
  • Blood D-xylose levels are generally considered more reliable than urine levels in children younger than 12 years old.
  • A test that looks at the lining of the small intestines (upper gastrointestinal series) may be used if Crohn's disease or another malabsorption syndrome is suspected. For more information, see the topic Upper Gastrointestinal Series.


  1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

  • Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

ByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerJerome B. Simon, MD, FRCPC, FACP - Gastroenterology
Last RevisedMarch 8, 2013

WebMD Medical Reference from Healthwise

Last Updated: March 08, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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