24-Hour Urinary Sodium Excretion Rate

Why This Test Matters

Your kidneys filter blood and control how much sodium (a mineral) stays in your body. Sodium is important for balancing fluids and nerve/muscle function. A 24-hour urine sodium test gives a full picture of your body’s sodium handling, which can reveal problems like kidney disease, excessive sweating, or conditions affecting fluid balance.

What to Expect Before the Test

You’ll collect all your urine for 24 hours, starting and ending the collection period at the same time (e.g., midnight to midnight). Drink normal fluids but avoid special diets or medications that could affect sodium levels unless instructed otherwise. Store the urine in a cool place until you deliver it to the lab.

How the Test Works

Your urine is tested for sodium content. The test calculates the total sodium excreted over the day, accounting for the volume of urine produced. This rate helps doctors compare how much sodium your body is losing to what’s typically expected for your size and health.

What the Results Mean

Results are usually reported as a rate (e.g., milligrams per day). Low results may suggest kidney problems, excessive sodium loss, or conditions like diabetes insipidus. High results could indicate kidney disease, excessive salt intake, or certain medications. Your doctor will interpret results in the context of your overall health.