Serum cystatin C is an indicator to assess early kidney injury, such as when there is nephritis, obesity-associated nephropathy and other diseases, this indicator will appear to increase, and often the increase will precede the abnormal urinalysis. When this indicator is abnormal, further examination of renal function, urine routine, urine microprotein, renal ultrasound and other items are needed to comprehensively understand the kidney condition. It is also necessary to evaluate some risk factors for the occurrence of kidney disease, such as diabetes, obesity, hypertension, etc. In terms of daily life, for kidney protection, we need to pay attention to not staying up late, overworking, not smoking, drinking and overeating, not abusing drugs, and eating a lighter diet with low salt and low fat.