Urine Sodium Mass Concentration (24-hour collection)

Why This Test Matters

Sodium is essential for nerve and muscle function, blood pressure regulation, and maintaining fluid balance. Chronic high or low sodium levels can lead to health issues like high blood pressure, kidney problems, or heart disease. A 24-hour urine sodium test provides a comprehensive picture of your body’s sodium excretion, which isn’t easily captured by a single blood or spot urine test.

When You Might Need This Test

Your doctor may recommend this test if you have symptoms like frequent urination, swelling (edema), high blood pressure, kidney disease, or if you’re on medications that affect sodium levels (e.g., diuretics). It’s also used to evaluate conditions like primary hyperaldosteronism or to monitor kidney function in certain chronic diseases.

How the Test Works

You’ll collect all your urine over a 24-hour period, typically starting after a clean void (first morning urine is often discarded). The sample is then sent to a lab for measurement. Sodium is measured in milligrams (mg) per 24-hour urine volume, often reported as mg/day.

What to Expect Before the Test

No special preparation is usually needed, but you may be asked to limit certain medications or foods that could affect sodium levels (like salt supplements). Always follow your doctor’s instructions precisely to ensure accurate results.