Glucose, (also known as D-glucose, dextrose, or grape sugar) is a simple sugar (monosaccharide) and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate. Glucose is one of the main products of photosynthesis and fuels for cellular respiration.

The name “glucose” comes from the Greek word glukus (γλυκύς), meaning “sweet”, and is the preferred name. The suffix “-ose” denotes a sugar.

Scientists can speculate on the reasons that glucose, and not another monosaccharide such as fructose, is so widely used in organisms. One reason might be that glucose has a lower tendency, relative to other hexose sugars, to react non-specifically with the amino groups of proteins. This reaction (glycation) reduces or destroys the function of many enzymes. The low rate of glycation is due to glucose’s preference for the less reactive cyclic isomer. Nevertheless, many of the long-term complications of diabetes (e.g., blindness, renal failure, and peripheral neuropathy) are probably due to the glycation of proteins or lipids.In contrast, enzyme-regulated addition of glucose to proteins by glycosylation is often essential to their function.