The severity of elevated urea nitrogen depends on the cause of its elevation. Elevated urea nitrogen can be due to physiologic or pathologic causes. Physiologic causes are generally less serious, while pathologic causes are generally more serious. 1. Physiological causes: Physiological causes such as eating too much protein, drinking too little water leading to blood concentration, blood loss, can lead to high urea nitrogen levels, at this time, pay attention to adjusting the diet structure, appropriate drinking water can make the level of urea nitrogen decreased. Physiological causes are not serious, after correcting the causative factors, the level will return to normal soon. 2. Pathological causes: Pathological causes first need to rule out the existence of renal diseases, such as acute nephritis, chronic glomerulonephritis, renal tuberculosis, renal tumors, renal failure and so on. Extra-renal causes can be seen in severe burns, upper gastrointestinal hemorrhage, severe infections, and urinary tract obstruction. Pathologic triggers tend to be more serious and require ruling out the presence of the above factors. The first step is to assess the presence of renal disease, which also needs to be diagnosed in conjunction with glomerular filtration rate and creatinine level, etc. Consultation with the nephrology department of a regular hospital is recommended.