What is being tested?This test measures the level of sodium in blood. Sodium is an
electrolyte present in all body fluids, and is vital to normal body function. It works to regulate the amount of water in the body, and to control blood pressure by keeping the right amount of water available (in some people, too much sodium from salt in the diet can contribute to high blood pressure). Your body tries to keep your blood sodium within a very small concentration range; it does so by:
- producing hormones that can increase (such as natriuretic peptides) or decrease (such as aldosterone) sodium losses in urine
- producing a hormone that prevents water losses (antidiuretic hormone [ADH], sometimes called vasopressin)
- controlling thirst (even a 1% increase in blood sodium will make you thirsty and cause you to drink water, returning your sodium level to normal.)
Abnormal blood sodium is usually due to some problem with one of these systems. When the level of sodium in the blood changes, the water content in your body changes. These changes can be associated with dehydration (too little fluid) or oedema(too much fluid, often resulting in swelling in the legs).
