What is this test?
This timed test measures the total sodium excreted in urine over a full day. Collecting every urine portion is essential because the laboratory calculates a daily total rather than interpreting one spot sample.
Why might it be ordered?
- To estimate sodium intake or assess fluid, blood-pressure or kidney-related questions.
- To monitor a known condition when your clinician needs a full-day excretion measurement.
What sample is needed?
All urine passed during the laboratory-defined 24-hour period is required. Use only the container supplied or approved by the laboratory.
How should you prepare?
Follow the laboratory protocol exactly. Usually you discard the first morning urine and record that time, collect every portion through the day and night, then include the urine passed at the same time the next morning. Confirm the container, storage and any diet or medicine instructions; do not change treatment on your own.
How should you understand the result?
Recent salt intake, diuretics and collection completeness strongly affect the result.
Sources and editorial status
This patient-facing text is an editorial draft. It should be approved by a laboratory physician before official publication.
- Laboratory Tests — MedlinePlus, U.S. National Library of Medicine
- How to Prepare for a Lab Test — MedlinePlus, U.S. National Library of Medicine
- How to Understand Your Lab Results — MedlinePlus, U.S. National Library of Medicine
- 24-hour urine collection — MedlinePlus, U.S. National Library of Medicine