Sodium, Serum


Sodium is the primary cation (positive ion) in extracellular fluids in animals and humans. Sodium ions play a diverse and important role in many physiological processes. One important function is signal transduction in the human central nervous system, which depends on sodium ion motion across the nerve cell membrane, in all nerves. Although the system for maintaining optimal salt and water balance in the body is complex. One of the primary ways in which the human body keeps track of loss of body water is through osmoreceptors in the hypothalamus which sense a balance of sodium and water concentration in extracellular fluids. Consequently, and in the case of increased sodium level, one feels thirsty.


High serum levels are associated with inadequate water intake (dehydration), Cushing’s syndrome and excessive saline therapy. Low serum levels are caused by vomiting, diarrhea, sweating, inappropriate antidiuretic hormone secretion (SIADH), edema, ascites, Addison’s disease, congestive heart failure and other clinical entities. Serum sodium is a predictor of cardiovascular mortality in patients with severe congestive heart failure.

Sample Type, Quantity & Conditions

1 ml Serum Stability: 14 Days at 15-25 °C 14 Days at 2-8 °C

Special Precautions

Normal Range

136 - 145 mmol/L

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