SODIUM
Normally, serum sodium levels range from 135 to 145 mEq/L (SI, 135 to 145 mmol/L)
The serum sodium test measures serum levels of sodium, the major extra-cellular cation. Sodium affects body water distribution, maintains osmotic pressure
of extracellular fluid, and helps promote neuromuscular function; it also helps maintain acid- base balance and influences chloride and potassium levels. Sodium is absorbed by the kidneys; a small amount is lost through the skin.