Urea is the major end product of protein nitrogen metabolism in humans. It constitutes the largest fraction of the nonprotein nitrogen component of the blood. Urea is produced in the liver and excreted through the kidneys in the urine. Consequently, the circulating levels of urea depend upon protein intake, protein catabolism and kidney function. Elevated urea levels can occur with dietary changes, diseases which impair kidney function, liver diseases, congestive heart failure, diabetes and infections.
