Glucose is a simple sugar, a monosaccharide, that has the molecular formula C6 H12 O6. Other forms of monosaccharides are such as fructose and galactose.

Glucose is used by our bodies as fuel for energy; they are the major starting points for cellular respiration which produces ATP.

When glucose levels in the blood are high, they are converted into glycogen in the liver and muscles (glycogenesis), and also stored as fat in adipose tissue. Insulin controls the levels of glucose in the body to maintain homeostasis.

Diabetes mellitus is a metabolic disease which occurs when glucose levels in the blood are too high due to ineffective insulin action or low insulin production.