Renal function test when used as part of creatinine clearance; crude marker for completeness of 24-hour urine collections when collected for other purposes
 
If the specimen is a 24-hour collection instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning). Screw the lid on securely. Transport the specimen promptly to the laboratory. Container must be labeled with patient's full name, date and time collection started, and date and time collection finished.