Cell Biolabs’ Creatinine Assay Kit measures creatinine levels in urine. Samples are compared to a known concentration of creatinine standard within a 96-well microtiter plate format. Samples and standards are incubated for 30 minutes with a reaction reagent which changes color from yellow to bright orange upon reacting with creatinine, forming the creatinine-picrate complex. The plate is read with a standard 96-well spectrophotometric microplate reader at 490 nm. Higher OD values correlate with high creatinine concentrations. Sample creatinine concentrations are determined by comparison with the known creatinine standards.