A nurse is teaching a client how to collect a 24-hour urine specimen for creatinine clearance. Which direction is essential to include?

• A. Discard the first voiding and record the time
• B. Collect urine only in the morning hours
• C. Keep the specimen at room temperature at all times
• D. Discard all urine after 12 hours and start anew

Answer: (A)

In a 24-hour urine collection for creatinine clearance, accuracy comes from capturing all urine produced during a full day. Start by discarding the first void and recording the exact start time, because urine produced before that moment isn’t part of the 24-hour total and would skew the result. From there, collect every subsequent urine for the next 24 hours and include the final void at the end of the period. Keeping the specimen properly stored (often refrigerated) preserves the sample’s integrity for accurate measurement. This approach differs from starting with a morning collection, stopping at 12 hours, or keeping the specimen at room temperature, which would lead to an inaccurate calculation.