D-xylose absorption test (25g oral load, mass concentration in plasma)
This test measures how well your intestines absorb the sugar D-xylose after drinking a special liquid containing 25 grams of it. It helps check for intestinal absorption problems, such as celiac disease or short bowel syndrome.
["Assesses gut absorption function with a simple oral sugar challenge."]
Key facts at a glance
- LOINC
- 1645-1
- Short code
- Xylose 2h p 25 g Xyl PO Bld-mCnc
- Synonyms
- Xylose 2h p 25 g Xyl PO Bld-mCnc
- Category
- chemistry
- Sample
- whole-blood
- Container
- Lavender-top (EDTA)
- Units
- N/A
- Ref low
- 20
- Ref high
- 400
- Fasting
- false
- Population
- adult
- Sex
- all
- Age range
- 18–65 years
- CPT
- 82670
- Specimen volume
- 3 mL
- Stability
- Room temperature: 4h, Refrigerated: 24h
- Hemolysis max
- 0
- Lipemia max
- 0
- Icterus max
- 0
- TAT
- 4–24 hours
- Order
- routine
Why This Test Matters
Your doctor may order this test if you have symptoms like chronic diarrhea, weight loss, or unexplained nutrient deficiencies, or if you’ve been diagnosed with conditions that affect how your intestines absorb nutrients. It’s also used to monitor intestinal health in certain chronic illnesses.
How the Test Works
You’ll drink a liquid containing 25 grams of D-xylose. Blood samples are taken before drinking and at specific intervals afterward to measure how much of the sugar remains in your bloodstream. This helps determine how efficiently your intestines absorbed it.
Preparation
No special preparation is needed, but avoid taking any medications that might affect digestion (like antibiotics or antacids) for 24 hours before the test. Follow your doctor’s instructions carefully.
What to Expect
The test usually takes about 4 hours. You’ll have blood drawn at multiple points, including right after drinking the solution and at 1, 2, and 3 hours later. Stay hydrated and rest comfortably during the process.
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.
Clinical Significance
Short name
D-Xylose Absorption Test
Frequently asked questions
Low absorption of D-xylose suggests malabsorption, which can indicate conditions like celiac disease, short bowel syndrome, or other gastrointestinal disorders. High absorption may be normal, but repeated testing or additional evaluation may be needed if symptoms persist.
What does a normal result mean? A normal result means your intestines absorbed the sugar well, but further testing may still be needed if you have ongoing symptoms or risk factors for absorption issues.
How long will I need to wait for results? Results are typically available within a few days to a week, depending on your lab’s processing time.
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