The normal range of blood urea nitrogen is usually 3.2-7.1 mmol/L, slightly lower in children and infants; the normal range of blood creatinine is 53-106 μmol/L for men and 44-97 μmol/L for women, and the reference values may vary slightly from hospital to hospital due to different testing methods. Blood urea nitrogen is the end product of protein metabolism, which is normally filtered through glomeruli and excreted in urine. Increased blood urea nitrogen is seen in organic renal damage, pre-renal oliguria, protein catabolism or excessive intake. Blood creatinine is a muscle metabolite that is normally filtered out of the body through the glomerulus and excreted in the urine. Increased blood creatinine is seen in conditions such as organic renal failure and prerenal oliguria. In the elderly and emaciated individuals creatinine is low, and if their creatinine is elevated, it is important to be alert for diminished renal function. It is recommended that patients with abnormal blood urea nitrogen and blood creatinine should go to the hospital in time, complete the relevant examinations under the guidance of the doctor, clarify the cause of the disease and actively treat it.