Xylose Absorption Test (Adult - 25g dose)
Ordering Recommendation
Quantitative Spectrophotometry
Tue, Thu
1-5 days  
New York DOH Approval Status
This test is New York DOH approved.
Submit With Order
Specimen Required
Patient Preparation
Patient should fast for 8 hours (Min: 4 hours) prior to administration of xylose.  
Fasting serum, five-hour urine, and two-hour serum according to the following instructions.  
Specimen Preparation
1. Just prior xylose administration, patient should empty his or her bladder (DO NOT collect this urine).
2. Just prior to xylose administration, collect first serum specimen (Min: 0.5 mL). Allow serum to clot completely at room temperature. Separate serum from cells ASAP or within 2 hours of collection. Label this specimen as "FASTING SERUM" and prepare for transport.
3. Give adults 25 g D-xylose in 250 mL water. Encourage the patient to drink an additional 250 mL water following the xylose dose. The patient may have water as desired, but no other food or fluids. Smoking should be prohibited. The patient should rest in a chair or on a bed until completion of test. Mild diarrhea is common following xylose ingestion.
4. Immediately following the xylose dose, collect all urine for the next five hours. Measure and record the volume, mix well, and remove a 5 mL aliquot (Min: 3 mL) and prepare for transport. Label this specimen as "FIVE-HOUR URINE." Record the total volume and the xylose dose given on the urine aliquot tube.
5. Two hours after administration of xylose dose, collect the second serum specimen (Min: 0.5 mL). Allow serum to clot completely at room temperature. Separate serum from cells ASAP or within 2 hours of collection. Label this specimen as "TWO-HOUR SERUM" and prepare for transport.
6. Record the xylose dose given and the total volume of the five-hour urine on the test request form.
Failure to include all required information will result in delay of turnaround time.
Storage/Transport Temperature
Unacceptable Conditions
Non-fasting specimens. Whole blood or unspun clot tubes. Grossly hemolyzed serum.  
The fasting serum specimen does not have a reference interval since it is used as a blank for the two-hour serum sample.
For children, refer to Xylose Absorption Test (Child) (ARUP test code 0020612).  
Ambient: 4 hours; Refrigerated: 1 week; Frozen: 1 month  
Reference Interval

Components Reference Interval
Serum, fasting specimen
(There are no reference intervals for the fasting serum specimen; it is used as a patient "blank" when testing the two-​hour specimen.)
17 years and older: None
Serum xylose, two hours following ingestion 17 years and older: 32-​58 mg/dL
Fraction of xylose dose excreted in five hours in urine 17-​64 years: 16-​40% of dose
65 years and older: 14-​40% of dose
Amount of xylose excreted in five hours in urine 17-​64 years: 4.0-​10.0 g/5 hours
65 years and older: 3.5-​10.0 g/5 hours
Interpretive Data
The xylose absorption test evaluates carbohydrate absorption by the mucosa of the proximal small intestine. In patients with renal deficiency, rely on the serum test only. In functionally anephric patients, the test is unreliable. A number of drugs can interfere with test results, including aspirin, atropine, colchicine, digitalis, indomethacin, MAO inhibitors, nalidixic acid, neomycin, opium alkaloids, and phenelzine. Nonfasting serum samples are often compromised by significant analytic interferences.

For those patients who do not tolerate the 25 g xylose dose, a 5 g dose can be used, refer to Xylose Absorption Test (Adult - 5 g dose) (0020615).  This change in dose must be noted on the test request form.
CPT Code(s)
Component Test Code*Component Chart NameLOINC
0020086Serum Xylose at 2 Hours10454-7
0020088Xylose Excretion % Dose 5 hr22630-8
0020600Xylose Excretion, g/5hr22626-6
0097110Total Volume19153-6
* Component test codes cannot be used to order tests. The information provided here is not sufficient for interface builds; for a complete test mix, please click the sidebar link to access the Interface Map.
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