Sodium Urine Test, 24-Hour

This test can be useful in determining the cause of a sodium imbalance. It is also useful for patients with kidney conditions to determine the cause of damage.

The Sodium Urine Test requires a 24-hour urine sample. The lab will provide a collection container and the patient will be instructed to collect all urine for a 24-hour period. Specific directions will be provided by the laboratory. Upon completion of the process, return the sample to the lab for processing. Results will be available within 1-2 days. A 24-hour sample is required because the amount of sodium in urine can vary throughout the day, making a single sample an inaccurate reflection of average sodium levels. The Sodium Urine Test may also be referred to as Na, for sodium’s chemical element symbol. Fasting is not required prior to or throughout the testing process.

Sodium is an electrolyte that aids in balancing the amount of fluid in the body and plays a role in certain processes such as muscle and nerve function. The body gets sodium from the foods we consume. It uses what it needs and excretes any excess in urine. Low sodium (hyponatremia) is commonly attributed to sodium loss due to a variety of conditions; rarely it can be attributed to inadequate intake. It may also be caused by excess water consumption or fluid accumulation. High sodium (hypernatremia) is typically caused by inadequate water consumption.

Sodium urine levels can be evaluated alongside blood levels to determine whether high levels in the urine are due to elevated blood levels (both results would be high) or loss of sodium (urine level would be high but blood level would normal or low). Inadequate sodium intake would result in low blood and urine levels.