24-Hour Urine Sodium Excretion Rate

Why This Test Matters

Sodium is essential for nerve and muscle function, blood pressure regulation, and maintaining fluid balance. The kidneys normally filter sodium from the blood and excrete it in urine. If your body retains too much sodium, it can lead to high blood pressure or fluid retention. If too little is excreted, it may indicate kidney problems or other health conditions.

What to Expect Before the Test

No special preparation is usually needed, but your doctor may advise you to avoid certain medications or foods that could affect sodium levels. You’ll collect all your urine over a 24-hour period, typically starting and ending at the same time each day. Store the urine in a refrigerator until you return it to the lab.

How the Test Works

The lab analyzes the total sodium content in your 24-hour urine sample. This is done using a method like ion-selective electrode (ISE) or colorimetric techniques to measure sodium concentration. The result is expressed in milligrams (mg) per day.

Possible Causes of Abnormal Results

Low sodium excretion (hyposodiumuria) may suggest kidney disease, excessive sweating, or certain medications. High sodium excretion (hyperosmuria) could indicate kidney dysfunction, excessive salt intake, or conditions like diabetes insipidus.