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Serum sodium
Definition:
This tests measures the amount of sodium in the blood. Alternative Names:
Sodium - serum; Na+ Text Continues Below
How the test is performed:
Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a band is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the band to swell with blood. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the band is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
In infants or young children, the area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding. How to prepare for the test:
The health care provider may advise you to withhold drugs that can affect the test. (See special considerations.) DO NOT, however, stop or change your medication without the knowledge and direction of your doctor. How the test will feel:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing. Why the test is performed:
This test is performed when you have symptoms of a sodium imbalance, or when you develop disorders associated with abnormal sodium levels.
Sodium is the major positive ion in the fluids outside of cells. The sodium level of your blood is the balance between the amount of sodium in the food and drinks you consume, and the amount your kidneys excrete. (In addition, a small percent is lost through the stool and sweat.)
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