Stool Reducing Sugars: Optimal Testing Recommendations

This test should only be ordered in children with short bowel syndrome to differentiate the source of diarrhea.

Guidelines for Test Utilization

What does the test tell me?

An abnormal test result only suggests that the small intestine is not able to metabolize and absorb sugars, resulting in osmotic diarrhea as a symptom. The test uses Benedict's reaction, in which cupric ions are reduced to cuprous ions while sugar molecules in stool are oxidized. The result is a color change from blue to red that correlates with the amount of sugar present.

Reducing sugars include certain disaccharides (lactose, galactose, and maltose) and monosaccharides (e.g., glucose and fructose). Although sucrose is not a reducing sugar, it is often metabolized by bacteria to glucose and fructose.

The reaction is not specific for sugars. Certain compounds (e.g., antibiotics with thiols, aldehydes, and ketones) can produce false-positive results.

False-positive results are often seen in normal, healthy infants and neonates. [back to top]

When should I order this test?

In very limited cases, stool reducing sugars may be helpful for children with short bowel syndrome to evaluate the relationship between dietary sugar ingestion and diarrhea. [back to top]

When should I NOT order this test?

Do not order for:

  1. Acute episodes of diarrhea, especially when gastroenteritis is suspected as this test is not predictive of recovery
  2. Suspected necrotizing enterocolitis in a premature neonate because the test lacks sensitivity
  3. Suspected lactose intolerance because monitoring clinical symptoms while altering the diet is more informative
  4. Adults, since sugars that pass through the small intestine will likely be metabolized by colonic bacteria [back to top]

How should I interpret the result?

A positive stool reducing sugars result is potentially due to a primary cause, such as a rare inborn error of metabolism (i.e., disaccharidase deficiency or monosaccharide transporter deficiency). Additionally, secondary, or acquired, causes may be due to injury of small intestinal villi from infection, surgery, autoimmune disease, drugs, or severe malnutrition. [back to top]

Is the test result diagnostic/confirmatory of the condition? If not, is there a diagnostic/confirmatory test?

No studies have demonstrated that detection of stool reducing sugars is an adequate screening test for primary or secondary causes of sugar malabsorption in children from resource-rich countries. Potential tests for the work-up of chronic, watery diarrhea in children should be selected based on clinical history and include: gastrointestinal viral/bacterial/parasitic panels, stool culture, lactose tolerance test, celiac disease testing, and tissue disaccharidase assay from intestinal biopsy. [back to top]

Are there factors that can affect the lab result?

This test is only valid if the sugar has been recently ingested, intestinal transit time is rapid, fresh stools are collected and immediately refrigerated/frozen to prevent bacterial degradation of the sugar, and the water portion of the stool is collected in the container (not absorbed into the diaper). If these conditions are not met, then the result may be a false negative. [back to top]

Are there considerations for special populations?

This test is potentially useful for children with short bowel syndrome. These children may need to be challenged with increased enteral nutrition for growth and development. Stool reducing sugars results might be helpful in assessing carbohydrate overload after increasing the rate or concentration of formula. [back to top]

What other tests might be indicated?

If an inborn error of metabolism is suspected (disaccharide deficiency or monosaccharide transporter deficiency), refer the patient to biochemical geneticist for appropriate challenge test or gastroenterologist for small intestinal biopsy. [back to top]


Counahan, R.; Walker-Smith, J. Stool and urinary sugars in normal neonates. Archives of disease in childhood 1976, 51 (7), 517-20.

Davidson, A. G.; Mullinger, M., Reducing substances in neonatal stools detected by Clinitest. Pediatrics 1970, 46 (4), 632-5.

Brenn, M.; Gura, K. M.; Duggan, C., Chapter 28 - Intestinal failure. In Manual of Pediatric Nutrition, 5th ed.; Sonneville, K.; Duggan, C., Eds. People's Medical Publishing House, 2014; pp 424-445.

Pinheiro, J. M.; Clark, D. A.; Benjamin, K. G. A critical analysis of the routine testing of newborn stools for occult blood and reducing substances. Advances in neonatal care: official journal of the National Association of Neonatal Nurses 2003, 3 (3), 133-8.

Gracey, M.; Burke, V., Sugar-induced diarrhoea in children. Archives of disease in childhood 1973, 48 (5), 331-6. 6.

Krom, F. A.; Frank, C. G., Clinitesting neonatal stools. Neonatal network: NN 1989, 8 (2), 37-40.

Last reviewed: June 2020. The content for Optimal Testing: the Association for Diagnostics & Laboratory Medicine’s (ADLM) Guide to Lab Test Utilization has been developed and approved by the the Academy of Diagnostics & Laboratory Medicine and ADLM’s Science and Practice Core Committee.

As the fields of laboratory medicine and diagnostic testing continue to grow at an incredible rate, the knowledge and expertise of clinical laboratory professionals is essential to ensure that patients received the highest quality and most useful laboratory tests. ADLM’s Academy and Science and Practice Core Committee have developed a test utilization resource focusing on commonly misused tests in hospitals and clinics. Improper test utilization can result in poor patient outcomes and waste in the healthcare system. This important resource geared toward medical professionals recommends better tests and diagnostic practices. Always consult your laboratory director to make sure these recommendations are appropriate for your patient population.