Lactic acid, also known as 2-hydroxypropanoic or milk acid, is a compound formed when glucose is broken down under certain conditions in a living creature or by some types of bacteria.In a person, for example, it is an important part of producing energy for strenuous exercise and helps with certain liver functions.ne common use for lactic acid in a human body is the formation of glucose. Moderate amounts of this acid can move through someone's blood stream and reach the liver, where it undergoes a process called gluconeogenesis to become glucose.