Lactose Tolerance Test

Medical Author:
Medical Editor:

What is the lactose tolerance test?

The lactose tolerance test is a test for diagnosing an intolerance of ingested lactose. Lactose intolerance is a genetic condition in which individuals are unable to digest and absorb the lactose sugar in cow's milk.

What is lactose intolerance?

Lactose intolerance is the inability to digest the sugar in milk, lactose. Milk is an important source of nutrition for children and even some adults. With normal lactose tolerance, all of the lactose is broken down (digested) in the intestine by an enzyme into two smaller sugars (galactose and glucose) which then are absorbed into the body. As a result, normally no lactose reaches the colon.

On the other hand, in individuals with lactose intolerance who lack the intestinal enzyme that breaks down the lactose, the ingested lactose is neither digested nor absorbed in the small intestine and reaches the colon where it is used by the bacteria in the colon. The bacteria produce chemicals that cause diarrhea, and also produce gas. Abdominal pain also may occur.

Medically Reviewed by a Doctor on 3/4/2014

Patient Comments

Viewers share their comments

Lactose Intolerance Test - Indications Question: Did your doctor administer a lactose intolerance test, or diagnose you based on diet?