- Creatinine is the waste product of creatine phosphate, a compound found in the skeletal muscle tissue. It is excreted entirely by the kidneys. Increased levels of creatinine indicate a slowing of the glomerular filtration rate. The creatinine clearance test consists of two components: a 24-hour urine collection and a blood sample.
- Conducting both urine and blood testing allows for the comparison of the serum creatinine level with the amount of creatinine excreted in the urine. This is a more sensitive indicator of kidney function than serum creatinine alone. The creatinine clearance normally decreases with aging due to a decline in the glomerular filtration rate. Since “clearance” means the amount of blood cleared of creatinine in 1 minute, a monitoring of the creatinine clearance rate provides valuable information regarding the progression of renal disease.
- A minimum creatinine clearance of 10 mL/minute is necessary to maintain life without the use of hemodialysis or peritoneal dialysis. The creatinine clearance rate is calculated by the following formula:
creatinine clearance = (Urine creatinine x urine volume)/creatinine in serum
Glomerular Filtration Rate
