Elevated blood BUN is an indicator of the metabolism of the human kidneys, and can be used to diagnose kidney failure, in conjunction with blood creatinine. If the blood urea nitrogen is elevated, it can also be seen in the case of protein catabolism and excessive intake, in addition to kidney disease. If the blood urea nitrogen is always at a high level, it is a pathological condition, and it should be clarified whether there are pathological changes of the kidney. When the blood urea nitrogen is elevated, it is recommended that patients promptly consult the nephrology department to clarify whether there are changes in the physiopathological state of the kidney. At the same time, review, with the blood creatinine level to understand the kidney function, and if necessary, kidney puncture biopsy, to clarify the type of pathology, for targeted treatment.