Lactate, also known as lactic acid or 2-hydroxypropanoic acid, is a carboxylic acid with the chemical formula CH3CH(OH)COOH. It is a byproduct of anaerobic metabolism, meaning it is produced when cells break down glucose for energy in the absence of oxygen. During intense physical activity or when oxygen supply is limited, such as during strenuous exercise, muscle cells produce lactate as a way to regenerate nicotinamide adenine dinucleotide (NAD+), which is necessary for glycolysis to continue.