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Sodium (Na) in Urine

A test for sodium in the urine is a 24-hour test or a one-time (spot) test that checks how much sodium is in the urine. Sodium is both an electrolyte and a mineral. It helps keep the water (the amount of fluid inside and outside the body's cells) and electrolyte balance of the body. Sodium is also important in how nerves and muscles work.

Most of the sodium in the body (about 85%) is found in blood and lymph fluid. Sodium levels in the body are partly controlled by a hormone called aldosterone, which is made by the adrenal glands. Aldosterone levels tell the kidneys when to hold sodium in the body instead of passing it in the urine. (See a picture of the adrenal glands camera.gif or the kidneys camera.gif.) Small amounts of sodium are also lost through the skin when you sweat.

Most foods have sodium naturally in them or as an ingredient in cooking. Sodium is found in table salt as sodium chloride or in baking soda as sodium bicarbonate. Many medicines and other products also have sodium in them, including laxatives, aspirin, mouthwash, and toothpaste.

Low sodium levels are uncommon and are most often caused by heart failure, malnutrition, and diarrhea.

Why It Is Done

A urine test to check sodium levels is done to:

  • Check the water and electrolyte balance of the body.
  • Find the cause of symptoms from low or high levels of sodium.
  • Check the progress of diseases of the kidneys or adrenal glands.

How To Prepare

You do not need to do anything before having this test.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

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WebMD Medical Reference from Healthwise

Last Updated: September 04, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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