In the fluorometric/colorimetric L-Lactate Assay Kit II, lactate specifically reacts with an enzyme mix to generate a product, which interacts with a lactate probe to produce a signal detectable as a color (570 nm) or as fluorescence (Ex/Em = 535/587 nm). The kit provides a convenient means for detecting L( )-Lactate in various biological samples, e.g. in circulating blood, cells, culture media, fermentation media, etc. at concentrations between 0.001 -10 mM. There is no need of pre-treatment or purification of samples.