Xylose Testing
Reviewed
Xylose testing measures xylose levels in blood and urine after drinking a xylose solution to assess how well your intestines absorb carbohydrates. It is used to help diagnose malabsorption disorders or evaluate why a child is not gaining weight. Results are interpreted by your healthcare professional.
Preparation and collection
Fast for 8 hours (or 4 hours for children under 9 years). For 24 hours before the test, avoid foods high in pentose sugar (e.g., jams, pastries, fruits). Tell your provider about all medicines you take; you may need to stop some before the test. Follow any additional instructions from your provider.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- The xylose solution may cause nausea.
- False-positive or false-negative results are possible; your provider will interpret results alongside symptoms, history, and other tests.
- This test is no longer routinely ordered and may not be available everywhere.
What to do next
Your healthcare professional will consider your symptoms, medical history, and the results of other tests to make a diagnosis. More tests may be needed before a diagnosis can be made.