Glucose is a monosaccharide sugar found in most plant and animal tissues. Cells in the body use glucose as their major source of energy and as an intermediate for many metabolic reactions. Glucose actually exists as two molecules that are mirror images of each other, D-glucose and L-glucose, but only D-glucose is biologically active in humans 1. Glucose is produced commercially from the breakdown of starch; corn starch is primarily used in the United States. Glucose is easily absorbed through the intestine and is used as the reference value to determine the glycemic index of foods, a measure of their effects on blood-glucose levels 2, 3.