Urea is found in our body in liver. When proteins travel in our body and they are used they leave behind ammonia, this ammonia is converted to urea in our body in order to excrete it, otherwise this ammonia can be dangerous.
The conversion of nitrogen metabolites in humans to urea is important step. Urea is formed from ammonia and carbon dioxide, this conversion takes place in liver. The formed urea is then transported to the kidney where it is excreted.