Determining circulatory levels of bile acids can be used to identify or diagnose certain liver diseases. In addition, elevated serum bile levels have been observed in intrahepatic cholestasis of pregnancy cases. Cell Biolabs’ Total Bile Acid Assay Kit is a simple fluorometric assay that measures the amount of total bile acid present in plasma, serum, tissue homogenates, or cell lysates in a 96-well microtiter plate format. The assay is based on an enzyme driven reaction: when bile acids are incubated in the presence of 3α-hydroxysteroid dehydrogenase (3α-HSD) and NAD+, NAD+ is converted to its reduced form NADH. Diaphorase then uses NADH to reduce resazurin to resorufin which is then detected fluorometrically. Sample bile acid concentrations are determined by comparison with a known bile acid standard. Each kit provides sufficient reagents to perform up to 100 assays, including blanks, bile acid standards and unknown samples.