Urea nitrogen is the metabolite of protein decomposition in the body, creatinine is the metabolite of muscle tissue creatine in the body, both are important indicators of kidney function examination, which can reflect the glomerular filtration rate. If urea nitrogen creatinine is elevated, it means that the patient has renal function damage, its pathogenesis is the damage of renal function, glomerulosclerosis, partial or complete loss of kidney excretion of toxins, and the accumulation of urea nitrogen creatinine in the body, so it is elevated. Urea nitrogen creatinine is a general term for metabolic waste in the body, and elevated levels can affect the function of various organs, which can be damaged over time. Diseases such as uremic lung disease and uremic encephalopathy can occur. For example, if the toxin invades the lungs and causes an infection in the lungs, and if the toxin invades the brain, it can cause neurological symptoms such as twitching of the limbs, coma, and even death.