Sodium (Na) in Urine

Urinary Sodium

Test Overview

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 an illustration 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.

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Author:	Jan Nissl, RN, BS	Last Updated: November 17, 2006
Medical Review:	Martin Gabica, MD - Family Medicine Avery L. Seifert, MD - Urology
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