Stool Reducing Substance

If a stool reducing-substances test is positive, contact your healthcare provider for evaluation. They may repeat testing, check stool pH, order a hydrogen breath test, and assess for infections. Management often includes treating dehydration, a supervised trial of a lactose- or simple-sugar–restricted diet, possible lactase enzyme supplements, and follow-up to monitor symptoms and growth, especially in infants and children.

Reducing substances are compounds that donate electrons to oxidizing agents, typically sugars with free aldehyde or ketone groups that reduce copper(II) in Benedict’s or Fehling’s tests to copper(I) oxide. In clinical practice, urine reducing substances indicate reducing sugars such as glucose, fructose or lactose, or certain metabolites and drugs, aiding detection of diabetes and inherited metabolic disorders.

Reducing substances in a stool test are sugars that can donate electrons, detected when unabsorbed carbohydrates (e.g., lactose, glucose) remain in feces. A positive result suggests carbohydrate malabsorption or disaccharidase deficiency, often causing osmotic diarrhea, abdominal pain, and failure to thrive in infants. It’s screened with simple chemical tests and prompts further evaluation (stool pH, specific sugar assays) to find the cause.

To test for reducing sugars in stool, collect a fresh sample in a clean container. Mix a small amount with an equal volume of warm distilled water, filter or strain, then add Benedict’s reagent or a Clinitest tablet per kit instructions. Heat in a boiling-water bath a few minutes and compare the color change (blue→green/yellow/orange/red) to a chart. Positive results need clinical confirmation.

Reducing substances in stool indicate unabsorbed reducing sugars from carbohydrate malabsorption. Common causes include lactase deficiency (primary or secondary after infections), congenital disaccharidase defects (sucrase‑isomaltase), small‑intestinal mucosal disease (celiac disease, Crohn’s), bacterial overgrowth, or excessive intake of simple sugars/fruit juices in infants. This leads to osmotic fermentation in the colon, causing bloating, gas and watery diarrhea.

Acidic stool usually means unabsorbed carbohydrates are being fermented by gut bacteria (common in lactose intolerance, celiac disease, or after antibiotics) or with viral gastroenteritis. It often causes loose, foul‑smelling, bubbly stools and gas. If you have severe abdominal pain, blood, high fever, or signs of dehydration, seek medical care. Diagnosis and treatment target the underlying cause and fluid replacement.