Urea is a waste product which is produced in the liver, dissolved and transported in the blood (in a concentration of 1.6-7.5 mM), and excreted by the kidney. Urea plays a very important role in protein catabolism, removal of toxic ammonia from the body, and the countercurrent system which allows for reabsorption of water and critical ions in the nephrons. Urea concentration is an important indicator for the medical clinicians to assess function of the kidney and other organs in patients. BioVision’s Urea Assay Kit II is based on Jung’s method with a modification that delivers more robust and sensitive data. The urea is condensed with o-phthalaldehyde (OPA), followed by a reaction to form a colored product with strong absorbance at 505 nm. This assay kit is fast, sensitive & easy to use. It can measure less than 10 μM urea in 96-well plate assay.