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D-xylose absorption test (25g oral load)

Published: August 9, 2026Updated: August 16, 2026

This test measures how well your small intestine absorbs the sugar D-xylose after drinking a special drink containing 25 grams of it. It helps check for intestinal malabsorption or damage.

Quick summary

Assesses gut function and absorption after a sugar drink.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
14953-4
Short code
Xylose 2h p 25 g Xyl PO Bld-sCnc
Synonyms
Xylose 2h p 25 g Xyl PO Bld-sCnc
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, unexplained weight loss, or signs of malabsorption (such as vitamin deficiencies). It can also help diagnose conditions like celiac disease, short bowel syndrome, or intestinal infections.

How the Test Works

You’ll drink a sweet liquid containing D-xylose, a simple sugar. Blood samples are taken before drinking and at set times afterward (usually 1 and 2 hours). The test measures how much sugar remains in your blood, indicating how well your intestines absorbed it.

Sample Collection Process

A healthcare provider will draw blood from a vein in your arm at specific times. You’ll need to fast for 4–6 hours before the test to ensure accurate results.

What to Expect Before the Test

Avoid dairy, high-fiber foods, or fatty meals for 24 hours before testing. Stay hydrated but skip alcohol and caffeine. Let your doctor know about any medications you take, as some may affect results.

Reference range

Premenopausal: 20-400 pg/mL; Postmenopausal: <30 pg/mLN/A

Specimen: whole-blood

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

What does a low absorption rate mean?
A reduced absorption of D-xylose suggests your small intestine may not be working properly, possibly due to damage, inflammation, or disease. This could indicate conditions like celiac disease, Crohn’s disease, or other intestinal disorders.
What if my results are normal?
Normal results suggest your intestines absorb nutrients efficiently. However, if you still have symptoms, other tests or evaluations may be needed to explore other causes of your concerns.
Does fasting affect this test?
Yes, fasting ensures the test measures true absorption. Skipping this step could lead to misleading results, as food in your stomach may interfere with how your body processes the sugar.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

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.

Medical Disclaimer

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