Test Catalog

Test ID: UREDF    
Reducing Substance, Feces

Useful For Suggests clinical disorders or settings where the test may be helpful

Assisting in the differentiation between osmotic and non-osmotic diarrhea


Screening test for:

-Diarrhea from disaccharidase deficiencies, (eg, lactase deficiency)

-Monosaccharide malabsorption

Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test

Fecal reducing substances (carbohydrates) aids in determining the underlying cause of diarrhea. Elevations in fecal reducing substances help distinguish between osmotic diarrhea caused by abnormal excretion of various sugars as opposed to diarrhea caused by viruses and parasites. Increased reducing substances in stool are consistent with, but not diagnostic of, primary or secondary disaccharidase deficiency (primarily lactase deficiency) or intestinal monosaccharide malabsorption. Similar intestinal absorption deficiencies are associated with short bowel syndrome and necrotizing enterocolitis.

Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.

Negative or trace

Interpretation Provides information to assist in interpretation of the test results

Negative: negative

Normal: < or =0.25 g/dL (trace)

Suspicious: >0.25 to 0.50 g/dL (grade 1)

Abnormal: >0.50 g/dL (grade 2-4)

Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances

This test has poor sensitivity for oligosaccharides.


Antibiotics can alter the intestinal flora and affect acid production.


False-positive reactions due to drugs (salicylates, penicillin, ascorbic acid, nalidixic acid, cephalosporins, and probenecid) are possible.


Feces may be contaminated with urine, in which case glycosuria will give false-positive results.


Diaper collections can be falsely decreased as the fluid portion containing water soluble sugars is absorbed into the diaper.


Ambient transport temperatures result in growth of bacteria that consume sugars resulting in falsely decreased values.

Clinical Reference Recommendations for in-depth reading of a clinical nature

1. Siddiqui HA, Salwen MJ, Shaikh MF, Bowne WB: Laboratory diagnosis of gastrointestinal and pancreatic disorders. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. Elsevier; 2017:306-323

2. Branski D: Disorders of malabsorption. In: Kleigman RM, Stanton BF, St..Geme JW, eds. Nelson Textbook of Pediatrics. Elsevier; 2016:1831-1850

3. Bhatia J, Prihoda AR, Richardson CJ: Parenteral antibiotics and carbohydrate intolerance in term neonates. Am J Dis Child. 1986;140(2):111-113

4. Book LS, Herbst JJ, Jung AL: Carbohydrate malabsorption in necrotizing enterocolitis. Pediatrics. 1976;57:201-204

5. Krom FA, Frank CG: Clinitesting neonatal stools. Neonatal Network. 1989;8(2):37-40

6. Qualitative methods for total reducing substances. In: Tietz Textbook of Clinical Chemistry. 2nd ed. 1994;968-969