Cystatin C is a small molecular weight protein produced by the metabolism of cystine in the body, and is commonly used as one of the reference standards for assessing renal function. Cystatin C is a small molecular weight protein that can be filtered out by the glomerulus, and its concentration in the blood serum is usually checked, with a normal range of 0.6-2.5 mg/L. Since cystatin is not secreted by the epithelial cells of the renal tubules and is not reabsorbed, the concentration of cystatin in the blood is relatively stable. If serum cystatin C increases, it suggests that renal function may be impaired, and there may be a decline in glomerular filtration function, etc. However, serum cystatin C is not the only indicator of renal function, but also needs to be combined with uric acid, blood creatinine, urinary tract ultrasound, blood urea nitrogen and other indicators in order to determine whether it is a renal function impairment. It is recommended that patients with abnormal cystatin C indicators should go to the hospital in time and follow the doctor’s instructions for standardized treatment.