Glycerol is a precursor for synthesis of triglycerides and of phospholipids in the liver and adipose tissue. In some organisms, glycerol can be converted into glucose by the liver and provide energy for cellular metabolism. The measurements of circulating glycerol are considered to reflect lipolysis and are therefore useful parameters to evaluate in different conditions. This colorimetric assay is based on a coupled enzymatic reaction of glycerol, in which the formed hydrogen peroxide is catalyzed by peroxidase and reacts with 4-aminoantipyrine to form the product dye. The color intensity of the reaction product at 540nm is directly proportional to glycerol level in the sample.