Xylose Testing
Xylose, also known as D-xylose, is a type of sugar ( carbohydrate ) that is normally easily absorbed by your intestines.
Xylose, also known as D-xylose, is a type of sugar ( carbohydrate ) that is normally easily absorbed by your intestines. A xylose test checks the level of xylose in both your blood and urine to see how well you absorb carbohydrates. Usually, your body digests in stages. The proteins , fats , and carbohydrates in the food you eat are: Broken down in the stomach by acid and enzymes (proteins that speed up certain chemical reactions in your body) Broken down further in your small intestines by pancreatic enzymes and bile (liquid made in your liver to help digest fats) Absorbed into your intestines to be used or stored If you don't have enough bile or pancreatic enzymes, the carbohydrates and other foods you eat can't be digested well. Lower-than-normal xylose levels can mean there is a problem with your body's ability to absorb nutrients. Xylose testing is no longer routinely ordered to check for malabsorption , and it may not be available everywhere. This test may be ordered as a follow-up test to other tests, such as a fecal fat test. Other names: xylose tolerance test, xylose absorption test, D-xylose tolerance test, D-xylose absorption test
Why is this test ordered? You may need this test if you have symptoms of a malabsorption disorder, which include: Chronic (long-lasting) diarrhea Abdominal (belly) pain Bloating (a feeling of fullness or swelling in your belly) Gas Weight loss for no known reason, or in children, not being able to gain weight
Clinical Interpretation
High levels of xylose are normal. It means that your intestines are absorbing the xylose. If your results are high, that may mean that your symptoms are not caused by malabsorption. If your results showed lower-than-normal levels of xylose in the blood or urine, it may mean you have a malabsorption disorder, such as: Celiac disease , a chronic (long-lasting) digestive and immune disorder that damages your small intestine. It is triggered by foods that contain gluten. Gluten is a protein found in wheat, barley, rye, and other grains. Crohn's disease , a chronic condition that causes inflammation in your digestive tract. Whipple disease, a rare condition that prevents the small intestine from allowing nutrients to pass into the rest of the body. Lower-than-normal levels may also be caused by an infection from a parasite , such as: Hookworm Giardiasis If your xylose blood levels were normal but urine levels were low , it may be a sign of kidney disease and/or malabsorption. You may need more tests before your provider can make a diagnosis. To understand the results of your xylose testing, your provider may consider your symptoms, medical history, and the results of other tests. Talk to your provider if you have questions about your or your child's results.
Clinical Protocol & Patient Advice
- 1
You will need to fast (not eat or drink) for eight hours before the test. Children younger than nine years old should fast for four hours before the test. For 24 hours before the test, you must avoid foods high in a type of sugar known as pentose, which is similar to xylose. These foods include jams, pastries, and fruits. Some medicines may affect your test results. You may need to stop taking certain medicines before this test, so tell your provider about everything you take. But don't stop taking any medicines unless your provider tells you to. Your provider will let you know if you need to do any other preparations.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.