The word "renal" refers to the kidneys. The terms "renal function" and "kidney function" mean the same thing. Health professionals use the term "renal function" to talk about how efficiently the kidneys filter blood. People with two healthy kidneys have 100 percent of their kidney function. Small or mild declines in kidney function-as much as 30 to 40 percent-would rarely be noticeable. Kidney function is calculated using a blood sample and a formula to find the estimated glomerular filtration rate (eGFR).
The eGFR corresponds to the percent of kidney function available.
For many people with reduced kidney function, a kidney disease is also present and will get worse. Serious health problems occur when people have less than 25 percent of their kidney function. When kidney function drops below 10 to 15 percent, a person needs some form of renal replacement therapy-either blood-cleansing treatments called dialysis or a kidney transplant-to sustain life.