The reference range of adult serum cystatin C is 0.6-2.5mg/L, and the results vary slightly depending on the examination machine. Cystatin C 1.47mg/L is within the normal range. Cystatin C in circulating blood is cleared almost exclusively by glomerular filtration and is an ideal endogenous marker to reflect changes in glomerular filtration rate. As a marker of glomerular filtration rate GFR, cystatin C has better sensitivity and specificity than serum creatinine. Cystatin C can evaluate the early impairment of renal filtration function in diabetic nephropathy, especially mild renal injury is more sensitive, need to monitor cystatin C regularly to observe the progress of the disease; cystatin C can also reflect the recovery of renal function, especially patients with delayed transplantation of renal function, and can be used to quickly diagnose acute rejection or damage caused by drug therapy. Patients with elevated cystatin C level should go to the hospital in time to improve the examination under the guidance of professional physicians, so as to clarify the diagnosis and early treatment.