Urea nitrogen is the clinical meaning of urea nitrogen, and the causes of elevated urea nitrogen are often seen in: 1, most commonly renal insufficiency, after the development of renal insufficiency, the glomerular filtration rate of patients will decrease, resulting in the body produced by the urea nitrogen can not be completely excreted through the urine, so urea nitrogen will appear elevated. 2, because urea nitrogen is the product of protein decomposition and metabolism in the body. If for some reason protein decomposition increases, or after eating too much protein, urea nitrogen will also appear to be elevated. The increase of protein decomposition is common in patients with fever and infection. 3, when there are prerenal factors, that is, after the kidney perfusion is insufficient, it will lead to high urea nitrogen. Commonly, factors such as hemorrhagic shock and dehydration can lead to elevated urea nitrogen.