High cystatin C usually indicates possible kidney disease. It can be seen in renal insufficiency due to various diseases, such as diabetic nephropathy and renal tubular dysfunction. Serum cystatin C ranges from 0.6 to 2.5 mg/L in adults. The original urinary cystatin C in the proximal tubule is almost completely taken up by the epithelial cells, decomposition, and does not return to the blood, only a trace amount of urinary excretion, therefore, the serum cystatin C level is a sensitive and specific indicator to reflect the glomerular filtration function. When diabetic nephropathy and other causes of renal insufficiency, glomerular filtration rate decreases, then the concentration of cystatin C in the blood increases; if the glomerular filtration rate is normal, and tubular dysfunction will also hinder the reabsorption of cystatin C, then the concentration of cystatin C in the urine rises significantly. Therefore, a high cystatin C level usually indicates the presence of kidney disease. If patients find high cystatin C, it is recommended to go to regular hospitals in time, complete the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.