24-Hour Urine Sodium Concentration (Mass Concentration)

Why This Test Is Done

Your doctor may order this test if they suspect conditions like high blood pressure (hypertension), kidney disease, or improper hormone function (such as aldosterone or antidiuretic hormone imbalances). It can also help evaluate how well you’re retaining or losing sodium, especially if you have certain medical devices like dialysis or take medications that affect sodium levels.

What to Expect Before the Test

No special preparation is needed, but you’ll need to collect all urine for 24 hours. Typically, you’ll start by emptying your bladder at home at the same time each morning, then collect every urine void for the next 23 hours. Store the sample in a refrigerator until you return it to the lab.

What the Test Results Mean

Results are usually reported as the total sodium amount excreted in milligrams (mg) over 24 hours. Higher-than-expected levels may indicate conditions like kidney problems or excessive sodium intake, while lower levels could suggest kidney retention or certain hormonal disorders.

Common Conditions Affecting Results

Abnormal results may point to conditions like primary hyperaldosteronism (excessive sodium loss), kidney failure, or conditions that affect how your body regulates fluids and electrolytes, such as heart disease or certain medications.