Glucose (Glc), a monosaccharide (or simple sugar) also known as grape sugar or corn sugar, is an important carbohydrate in biology. The living cell uses it as a source of energy and metabolic intermediate. Glucose is one of the main products of photosynthesis and starts cellular respiration in both prokaryotes and eukaryotes. The name comes from the Greek word glykys, meaning "sweet", plus the suffix "-ose" which denotes a sugar.

Two stereoisomers of the aldohexose sugars are known as glucose, only one of which (D-glucose) is biologically active. This form (D-glucose) is often referred to as dextrose monohydrate, or, especially in the food industry, simply dextrose (from dextrorotatory glucose). This article deals with the D-form of glucose. The mirror-image of the molecule, L-glucose, cannot be metabolized by cells in the biochemical process known as glycolysis.


The chemical D-glucose is sometimes referred to as dextrose, a historical name that derives from dextrorotatory glucose because a solution of D-glucose in water rotates the plane of polarized light to the right . However, the D- in D-glucose refers to a chiral chemical similarity property in sugars, not the property of rotating light . For this reason, the D- and L- designations in sugars do not perfectly predict optical rotation, and do not refer to this property.

Starch and cellulose are polymers derived from the dehydration of D-glucose. The other stereoisomer, called L-glucose, is rarely found in nature.