D-Xylose is a simple sugar, or monosaccharide, that is found in various plants, particularly in the cell walls of trees and some fruits. It is a five-carbon sugar, which distinguishes it from more common six-carbon sugars like glucose and fructose. D-Xylose plays a role in the structure of polysaccharides and is important in the production of certain food products and sweeteners. In medicine, D-Xylose is used in a diagnostic test to assess the absorption capacity of the intestines. This test helps determine if the body is properly absorbing nutrients, which can be crucial for diagnosing conditions like celiac disease or other malabsorption syndromes.