Xylose 2-Hour Serum/Plasma Concentration after 25 g Xylose Dose
This test measures how much xylose (a simple sugar) is present in your blood two hours after you drink a 25-gram dose of xylose, to help assess how well your small intestine absorbs sugars.
["The two-hour xylose level reflects how well the upper small intestine absorbed the sugar, which can help evaluate malabsorption."]
Key facts at a glance
- LOINC
- 15002-9
- Short code
- Xylose 2h p 25 g Xyl PO SerPl-sCnc
- Synonyms
- Xylose 2h p 25 g Xyl PO SerPl-sCnc
- Category
- chemistry
- Sample
- serum
- Container
- Red-top tube (SST)
- Units
- N/A
- Ref low
- 20
- Ref high
- 400
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82670
- Specimen volume
- 5 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
- Hemolysis max
- 500
- Lipemia max
- 1000
- Icterus max
- 500
- TAT
- 4–24 hours
- Order
- routine
What This Test Measures
Xylose is a simple sugar that is absorbed mainly in the upper part of the small intestine. After you drink a measured 25-gram dose, a blood sample is taken two hours later and tested to see how much xylose made it into your bloodstream.
Why Your Provider May Order It
Your provider may order this test if you have ongoing diarrhea, weight loss, or other signs that your intestines are not absorbing nutrients properly. Results can help point toward malabsorption and guide further testing.
How the Test Is Done
You will likely be asked to fast for several hours before the test. You then drink the 25-gram xylose solution, and your blood is drawn two hours later. Follow your care team's specific instructions about fasting, medications, and timing.
How to Prepare
Tell your provider about all medicines and supplements you take, since some can affect results. Follow any fasting or diet instructions given to you, and arrive at the scheduled time so the two-hour collection is accurate.
Reference range
Premenopausal: 20-400 pg/mL; Postmenopausal: <30 pg/mLN/A
No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.
Clinical interpretation
How abnormal results are interpreted and what conditions they suggest.
The xylose absorption test helps assess carbohydrate absorption in the small intestine; abnormal results may occur with small-intestine malabsorption or other conditions, but results must be interpreted alongside your symptoms and other tests. Because methods vary between laboratories, your provider will explain what your specific result means.
Short name
D-Xylose Absorption Test (2-Hour)
Frequently asked questions
Does an abnormal result mean I definitely have malabsorption?
Can my medications affect the test?
Will I need to fast before this test?
Sources
- 1
- 2Lab Tests OnlineSource
- 3
Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.
This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 16, 2026. · Read our editorial policy