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Test ID: CHOU Carbohydrate, Urine

Reporting Name

Carbohydrate, U

Useful For

Screening for conditions associated with increased excretion of fructose, galactose, and xylose


This test is not recommended as a follow up test for abnormal newborn screening for galactosemia.

Reflex Tests

Test ID Reporting Name Available Separately Always Performed
GALU Galactose, QN, U Yes No

Testing Algorithm

Testing begins with carbohydrate analysis. If qualitative results are normal or abnormal but not indicative of galactose, testing is complete.


If qualitative results indicate the presence of galactose, then quantitative testing for galactose will be performed at an additional charge.

Specimen Type


Ordering Guidance

This test is not appropriate for evaluation of an abnormal newborn screen for galactosemia. For those cases, order GCT / Galactosemia Reflex, Blood and consider GAL1P / Galactose-1-Phosphate, Erythrocytes and GATOL / Galactitol, Quantitative, Urine.

Specimen Required

Supplies: Urine Tubes, 10 mL (T068)

Container/Tube: Plastic, 10-mL urine tube

Specimen Volume: 5 mL

Collection Instructions: Collect an early-morning (preferred) random urine specimen.

Specimen Minimum Volume

1 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Frozen (preferred) 21 days
  Refrigerated  21 days

Reference Values


If positive, carbohydrate is identified.

Day(s) Performed


Test Classification

This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information


82760-Galactose (if appropriate)

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CHOU Carbohydrate, U 16550-6


Result ID Test Result Name Result LOINC Value
9255 Carbohydrate, U 16550-6

Clinical Information

Carbohydrates are a group of mono-, di-, and oligosaccharides of endogenous and exogenous sources. Their presence frequently reflects dietary consumption but can indicate specific pathology if either a particular saccharide or a particular excretory pattern is present. Most saccharides (except glucose) have low renal thresholds and are readily excreted in the urine.


In addition to several other saccharide species, chromatography of urinary saccharides identifies galactose and fructose and is, therefore, useful to screen for inborn errors of galactose and fructose metabolism. Xylose may also be detected in individuals with hereditary pentosuria, a benign trait with high frequency among individuals with Ashkenazi Jewish descent.


An interpretive comment is provided.

Clinical Reference

1. Steinmann B, Gitzelmann R, Van den Berghe G: Disorders of fructose metabolism. In: Valle D, Antonarakis S, Ballabio A, Beaudet A, Mitchell GA, eds. The Online Metabolic and Molecular Bases of Inherited Disease McGraw-Hill; 2019. Accessed January 09, 2020. Available at

2. OMIM. #260800 Pentosuria; PNTSU. Johns Hopkins University; 1986. Updated July 9, 2016. Accessed April 23, 2021. Available at

3. Gaughan S, Ayres L, Baker P II: Hereditary fructose intolerance. In: Adam MP, Ardinger HH, Pagon RA, et al, eds. GeneReviews [Internet]. University of Washington, Seattle;2015. Updated February 18, 2021. Accessed April 23, 2021. Available at

Report Available

8 to 15 days

Method Name

Thin-Layer Chromatography (TLC), Qualitative


Biochemical Genetics Patient Information (T602) in Special Instructions.

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: