Glucose is a form of carbohydrate known as a simple sugar, or monosaccharide. Plants produce glucose through photosynthesis, and humans consume it in the form of fruit and corn syrup. Glucose is also known as blood sugar because it is constantly present in the human bloodstream.
Glucose is the body's main form of energy, powering muscles and providing the brain with its only energy source. Insulin helps to process carbohydrates into glucose during digestion in order to support the body's functions. Excess glucose is stored in the liver and muscles in the form of glycogen. When these reserves are depleted, the body breaks down muscle and fat to obtain energy.