Creatinine is a normal product of muscle metabolism (breakdown) and is eliminated through the urine. The level of creatinine in the blood depends on a person’s muscle mass and the quality of their renal (kidney) function. Calculation of the estimated glomerular filtration rate (eGFR) allows for variations in people’s muscle mass to be taken into account when evaluating their kidney function.
The eGFR (expressed in ml/min/1.73 m2) represents the volume of blood (in millilitres) purified by the kidneys every minute. The calculation is adjusted for a normal-size person (body surface area of 1.73 m2) between 18 and 70 years of age. The results are interpreted as follows:
Greater than 90 ml/min/1.73 m2: normal kidney function.Between
60 and 89: possibly slight decrease in kidney function. Between
30 and 59: moderate decrease in kidney function.Between
15 and 29: severe kidney dysfunction.
eGFR results below 15 are observed in people with acute kidney failure before their hemodialysis treatment. For people who are likely to have more or less muscle mass (body builders, amputees, and people with muscular degeneration diseases, who are strict vegetarians or are extremely obese, etc.), it is preferable to use the real glomerular filtration rate (creatinine clearance) rather than the estimated rate (eGFR) as a measure of kidney function.