Creatinine clearance is a way for doctors to check if the kidneys are working properly. Some medications are processed out of the body by the kidneys. If the kidneys are not working as they should, the medication could build up, so it is important to know if the kidneys are functioning well. Creatinine is a naturally occurring substance in the body that also happens to be processed by the kidneys. By measuring how well the body processes this substance, a doctor can estimate how well it can handle a medication.
Collect a blood sample from the patient and run a test for serum creatinine levels. Collect a 24-hour urine sample from the patient and run a test for creatinine levels.
Calculate the creatinine clearance by using this formula: (urine creatinine x urine volume)/(1440 x serum creatinine) where serum and urine creatinine are measured in mg/dl and urine volume is measured in ml.
Calculate creatinine clearance from serum creatinine only by using this formula: [(140-age) x weight]/72 x serum creatinine where the weight is measured in kg and the serum creatinine is measured in mg/dl. For females, multiply the result by 0.85.
Calculate creatinine clearance from serum creatinine using an alternate method by using this formula: [98 - (0.8 x (age-20))]/serum creatinine where age is rounded to the nearest decade and serum creatinine is measured in mg/dl. For females, multiply result by 0.9.