High serum cystatin C measurement is indicative of early kidney damage, such as chronic glomerulonephritis, diabetic nephropathy, hypertensive nephropathy. In addition, kidney transplantation and the use of chemotherapeutic drugs can also lead to an increase in this indicator. Cystatin C freely passes through the glomerular filtration membrane. Almost all of the cys C in the original urine is taken up and broken down by epithelial cells in the proximal tubule and does not return to the bloodstream, and only a trace amount is excreted in the urine. Therefore, serum cys C level is a sensitive and specific indicator of glomerular filtration function. If serum cystatin C is high, it is recommended to go to the nephrology department of the hospital for examination to find out the cause. It also needs to be combined with urine routine, urine microalbumin, 24-hour urine protein quantification, renal function and renal ultrasound to further determine whether it is an early state of kidney disease. In the case of elevated serum cystatin C, it is necessary to go to the hospital in time to clarify the cause and follow the doctor’s instructions for treatment.