Low cystatin C generally has no special clinical significance and generally indicates good glomerular filtration. Cystatin C is a protein synthesized by the body’s own nucleated cells, with a normal range of 0.32-1.15 mg/L. Its production is stable and is not affected by age, sex, diet, body weight, or other factors, and it is removed only by glomerular filtration. Some of the filtered cystatin C can be reabsorbed by the renal tubules, but it is usually metabolized and broken down completely in the cells and does not flow back into the bloodstream. Therefore, the concentration of cystatin C in the serum is mainly dependent on the glomerular filtration rate, which is a more sensitive indicator for determining the early stage of renal function impairment. Low cystatin C is generally not of great clinical significance, the patient may have a low basal level of cystatin C. If there are no other symptoms, no special treatment can be done. If there are no other symptoms, no special treatment can be done. On the other hand, an increase in cystatin C is mainly due to the damage of renal function, resulting in a decrease in glomerular filtration rate, which requires prompt medical attention, further examination to clarify the cause of the disease, and treatment under the guidance of a physician.