The standard glomerular filtration rate for a 75-year-old is about 45 to 85 ml/min, which is slightly lower than normal. The glomerular filtration rate in normal adults is usually 80 to 120 ml/min, but it declines by 10 ml/(min.1.73m2) per decade with age, especially after age 30. Glomerular filtration rate is the amount of plasma fluid filtered out through the glomerulus per unit of time (min), i.e., the amount of ultrafiltrate produced by the kidneys on both sides per unit of time (min). Glomerular filtration rate cannot be measured directly, but can only be inferred by using some marker of renal clearance or plasma clearance. The glomerular filtration rate of 75 year olds is relatively reduced due to the aging of various organ systems in the body and the impairment of renal function. The glomerular filtration rate may be even lower if the elderly have a combination of underlying renal disease or other conditions that affect renal function. Glomerular filtration rate often reflects the glomerular filtration function and tubular reabsorption function of the kidneys, and it is generally necessary to combine with routine urinalysis, renal function, and urological ultrasound to comprehensively determine whether there is any abnormality in renal function. If the elderly have low glomerular filtration rate and other renal impairment, it is recommended to go to the regular hospital in time, under the guidance of the doctor to standardize the treatment.