Elevated cystatin C indicates the presence of renal impairment. Cystatin C is a test that reflects kidney function. If cystatin C is elevated, it indicates the presence of renal impairment. Cystatin C has certain advantages compared with creatinine and urea, which are affected by exercise, diet, gender, age, weight and other factors. For example, if a patient has had strenuous exercise or eaten a lot of protein-rich food before checking creatinine and urea, or if the patient is a young male with high muscle content, it can lead to high creatinine and urea, while cystatin C is not affected by these factors and is a more accurate indicator of kidney function. Currently, cystatin C is gradually replacing creatinine and urea as more sensitive indicators of kidney function impairment.