LDH Cytotoxicity Assay kit is a colorimetric assay that quantitatively measures lactate dehydrogenase (LDH), a stable cytosolic enzyme that is released into the cell culture supernatant upon damage of the cytoplasmic membrane. Released LDH in culture supernatants is measured with a 30-minute coupled enzymatic reaction: LDH oxidizes lactate to pyruvate which then reacts with tetrazolium salt WST-1 to form formazan. The increase in the amount of formazan produced in culture supernatant directly correlates to the increase in the number of lysed cells. The formazan dye is water-soluble and can be measured by 490 nm absorbance using a standard ELISA plate reader. The LDH-cytotoxicity assay is fast, sensitive, convenient, and precise, and is applicable to a variety of cytotoxicity studies.