Urea measurement is a program in renal function test. By testing the level of urea nitrogen in human blood, we can judge whether there is any problem in the function of kidney and it is an important indicator to judge the glomerular filtration rate. When the kidney function is normal urea nitrogen will be filtered in the glomerulus of the kidney and then reabsorbed by the renal tubules, only a small part of it can enter into the blood. When the human body suffers from pyelonephritis, glomerulonephritis, renal cancer, and blood volume insufficiency, it can cause renal failure, which can lead to uremia, resulting in urea nitrogen can not be reabsorbed, so that it can enter into the blood in large quantities. If there is low urea nitrogen, it is related to too little protein intake in the diet, abnormal renal function and liver failure. Urea nitrogen is significant in determining renal function and is a commonly used laboratory test in clinic, so when there is abnormal urea nitrogen, pay attention to it and consult the doctor in time.