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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 
or the
kidneys .) 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.
Too much sodium in the diet may raise blood pressure in some people. For those who have high blood pressure, eating foods with a lot of sodium makes their chance of heart disease, stroke, and kidney damage higher. Heart failure gets worse when too much sodium is eaten. It increases the amount of water the body holds in and this causes swelling of the legs and hands. Some people have problems when they eat more than 4,000 milligrams (mg) of sodium per day.
Low sodium levels are uncommon and most often occur as a side effect of taking medicines that make you urinate more, such as diuretics. Severe diarrhea or vomiting or heavy sweating may also cause low sodium levels.
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?).
WebMD Medical Reference from Healthwise
Last Updated:
September 01, 2010
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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