A normal creatinine but low glomerular filtration rate usually indicates impaired renal function or is seen in elderly patients. Creatinine is the metabolic end product of creatine in muscle tissue. Creatinine is not bound to protein in the blood and passes freely through the glomerulus, making it the most commonly used indirect indicator of glomerular filtration. When the renal parenchyma is damaged and the glomerular filtration rate is reduced to a critical point (when the glomerular filtration rate drops to 1/3 of normal), the blood creatinine concentration will rise significantly. Therefore, although creatinine is within the normal range, it does not completely mean that the kidneys are free of diseases, such as nephritis, kidney stones, pyelonephritis, etc. Blood creatinine can often be normal in patients with these diseases, but renal function may have been impaired, and thus the phenomenon of low glomerular filtration rate with normal creatinine may occur. If patients find abnormal renal function, it is recommended to go to regular hospitals in time, improve the examination to clarify the cause of the disease, and then give targeted treatment or therapy under the guidance of the doctor.