stool reducing substance test

What is a stool reducing substances test?

Stool (or faecal) reducing substances is a stool sample test used to diagnose lactose intolerance (and some rare metabolic abnormalities). Lactose intolerance can be caused by a prolonged or severe episode of viral gastroenteritis.

How is a stool reducing substances test performed?

The faecal reducing substances test is performed in a laboratory, on a sample of stool as small as 5 grams.
Unfortunately this sample needs to be delivered to the laboratory as soon as possible, preferably within 1 hour. This is because lactose (or other sugars) in the stool will normally be broken down by chemical processes within 2-4 hours afetr the specimen is produced.

Why would you need a stool reducing substances test?

Faecal reducing substances may be ordered by your doctor for symptoms suggestive of lactose intolerance, for example frequent loose stools, particularly if they are frothy in nature.

Lactose intolerance may occur after a prolonged episode of viral gastroenteritis, due to inadequate absorption of the sugar lactose by a damaged intestinal lining.

Other conditions, in which other sugars, such as glucose, galactose and fructose are not absorbed properly, can also cause a positive test for reducing sugars in the stool.