A patient is ordered for creatinine clearance. How should the nurse collect the specimen?

The correct method for collecting a specimen for creatinine clearance is the 24-hour urine specimen. This test measures how well the kidneys are filtering creatinine from the blood over a full day, providing a comprehensive view of kidney function.

During this 24-hour collection period, all urine produced must be collected to ensure accurate results, as creatinine levels fluctuate throughout the day. This collection method accounts for variations in urinary output and concentration, enabling a more precise assessment of renal function.

In contrast, other options like a 48-hour urine specimen, which would extend beyond the necessary duration for a standard creatinine clearance assessment, as well as first morning and random urine samples, would not provide the comprehensive data required. First morning urine captures a single point in time, which would not reflect the variability in kidney function over an entire day. Random urine samples cannot ensure that all urine production during the testing period is accounted for, making them insufficient for evaluating creatinine clearance.