BiochemistryGastroenterology

Stool for Reducing Substance

Normal Range
Negative or < 0.25 g/dL (Trace)
Sample Type
Fresh Stool
Fasting
No
Unit
mg/dL

Function

This test detects the presence of reducing sugars in the stool. Most carbohydrates are absorbed in the small intestine. If they are not absorbed (malabsorption), they pass into the large intestine where they can be detected as 'reducing substances.' These sugars include lactose, fructose, and galactose.

Why it is Ordered

It is primarily used to investigate diarrhea and failure to thrive in infants and children. It helps diagnose sugar malabsorption, which is often a result of enzyme deficiencies. Because unabsorbed sugars draw water into the intestine (osmosis), they cause watery, acidic diarrhea that can lead to rapid dehydration in young patients.

Associated Conditions

  • Lactose Intolerance: Deficiency of the lactase enzyme.
  • Sucrose Malabsorption: Although sucrose is not a reducing sugar, it can be broken down by bacteria into reducing sugars, sometimes giving a positive result.
  • Short Bowel Syndrome: Reduced surface area for absorption.
  • Viral Gastroenteritis: Can cause temporary, secondary lactose intolerance.

Check Your Result

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mg/dL

Enter your lab result to see where you stand compared to the standard reference range.

Why Context Matters

The stool sample must be fresh (ideally tested within 30 minutes to 1 hour) because bacteria in the stool will rapidly consume the sugars, leading to a false-negative result. Also, if the patient is on a restricted diet or has not consumed sugar recently, the test may not show the underlying malabsorption. A second opinion may involve a 'Breath Hydrogen Test' or a trial of an elimination diet to confirm findings.

Lab ranges are statistical averages, not biological laws. "Normal" for a 20-year-old male isn't normal for a 60-year-old female.

Clinical References

Source-of-truth databases and clinical guidelines for Stool for Reducing Substance:

Research & Guidelines

Related Indicators

Pleural Fluid ADA Levels

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CSF ADA Levels

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Pandy's Test

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DR

Medically Reviewed by Dr. Binoy Babu, MBBS

Board Certified Doctor • 10+ Years Clinical Experience

Dr. Babu is a practicing physician dedicated to empowering patients with clear, actionable medical information. He founded 2opi to bridge the gap between complex lab reports and patient understanding, ensuring everyone has access to a reliable second opinion.

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