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Test ID: CHOU Carbohydrate, Urine

Reporting Name

Carbohydrate, U

Useful For

Screening for disorders with increased excretion of fructose, glucose, galactose, disaccharides, oligosaccharides, and succinylpurines

Reflex Tests

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

Testing Algorithm

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

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

If qualitative results indicate the presence of glucose, then random glucose testing will be performed at an additional charge.

Specimen Type


Specimen Required

Container/Tube: Plastic, 10-mL urine tube (T068)

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
Urine Frozen (preferred) 21 days
  Refrigerated  21 days

Reference Values


If positive, carbohydrate is identified.

Day(s) and Time(s) Performed

Monday; 11 a.m.

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 U.S. Food and Drug Administration.

CPT Code Information


82760-Galactose (if appropriate)

82945-Glucose (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

Saccharides (also called 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.


The presence of saccharides in urine is seen in some inborn errors of metabolism. Urine tests for reducing substances (eg, copper reduction test) are often used to screen for those disorders. However, in addition to sugars, a number of other substances present in biological fluids (eg, salicylates, uric acid, hippuric acid, ascorbic acid) have reducing properties. Conversely, some saccharides such as sucrose and trehalose do not have reducing properties. Other saccharides present at low concentrations may not be identified by reducing tests. Substances in urine may inhibit glucose oxidase-based tests and, also, other saccharides of diagnostic importance may be present along with glucose in urine. Chromatography of urinary saccharides is, therefore, required in many instances to identify the particular species of saccharide present. Any specimen tested for urinary carbohydrates is concurrently tested for the presence of succinyl nucleosides to screen for inborn errors of purine synthesis.


An interpretive comment is provided that includes the name of the identified saccharide and the probable source.

Clinical Reference

1. Steinmann B, Gitzelmann R, Van den Berghe G: Disorders of Fructose Metabolism In The Online Metabolic and Molecular Bases of Inherited Disease. Edited by D Valle, AL Beaudet, B Vogelstein, et al. New York, McGraw-Hill, 2014, Accessed February 20, 2018. Available at:

2. Race V, Marie S, Vincent M, et al: Clinical, biochemical and molecular genetic correlations in adenylosuccinate lyase deficiency. Hum Mol Genet 2000 Sep 1;9(14):2159-2165

Analytic Time

8 days

Method Name

Thin-Layer Chromatography (TLC), Qualitative


1. Biochemical Genetics Patient Information (T602) in Special Instructions.

2. If not ordering electronically, complete, print, and send an Inborn Errors of Metabolism Test Request (T798) with the specimen.

Mayo Clinic Laboratories | Genetics and Pharmacogenomics Catalog Additional Information: