Glucose is a simple sugar (monosaccharide) with the chemical formula C₆H₁₂O₆ that serves as the main source of energy for the human body; it is produced when carbohydrates from foods like rice, bread, fruits, and potatoes are digested, then absorbed into the bloodstream and transported to cells where it is broken down to produce ATP (energy). The brain especially depends heavily on glucose for proper function. Any extra glucose is stored in the liver and muscles as glycogen or converted into fat for long-term storage. Blood glucose levels are tightly controlled by hormones such as insulin, which lowers blood sugar by helping cells absorb glucose, and glucagon, which raises blood sugar when it becomes too low. Abnormal glucose levels can lead to conditions like diabetes (high blood sugar) or hypoglycemia (low blood sugar).