Urea nitrogen, a product of protein catabolism metabolism. The most common reasons for its increase: 1. renal insufficiency. Urea nitrogen in the body will increase because it cannot be excreted through the urine after kidney insufficiency. 2. Diseases that lead to increased protein decomposition will lead to an increase in urea nitrogen. For example, infections, gastrointestinal bleeding, hyperthyroidism and other such diseases will lead to increased protein breakdown, and thus urea nitrogen will also be elevated. 3. Some of the prerenal elements will also lead to elevated urea nitrogen. For example, dehydration, shock, burns, etc., these lead to inadequate perfusion of kidney tissues, and then lead to an increase in urea nitrogen.