The D-xylose absorption test is commonly used to determine how well a person's small intestine absorbs sugar. This test is useful in diagnosing chronic diarrhea, malabsorption syndromes, and intestinal problems. Some synonyms for the D-xylose absorption test include the D-xylose tolerance test, D-xylose sugar test, and the D-xylose blood test. All these terms refer to the same type of diagnostic test used to evaluate intestinal function. The D-xylose absorption test is a simple, non-invasive test that involves drinking a sweetened solution containing the sugar D-xylose, followed by collecting blood or urine samples to measure the amount of D-xylose absorbed by the body.