Clinical diagnosis of renal failure cannot be based on serum cystatin C level. Serum cystatin C is one of the renal function test indicators, which can reflect the glomerular filtration function of the kidney more sensitively and specifically, compared with the serum creatinine and blood urea nitrogen levels, which can reflect the early damage of renal function more sensitively. However, to determine whether there is kidney failure or not, it also needs to be decided according to the glomerular filtration rate of the patient. However, the increase of serum cystatin C level can only suggest that the glomerular filtration function is impaired, which represents renal insufficiency, but the degree of elevation of this index is not able to directly assess whether the impairment of renal function has reached the level of renal failure. The assessment of renal failure needs to be combined with the patient’s serum creatinine, urine output and other indicators, and can not be diagnosed by relying on the serum cystatin C level alone. For patients with abnormal serum cystatin C, it is recommended to consult regular hospitals and improve relevant examinations under the guidance of physicians for clear diagnosis and treatment.