Serum sodium

Sodium in the body is mainly derived from the salt in food and absorbed into the blood through the intestine, of which 47% is in the bones. About 10% exists in the intracellular fluid and 44% exists in the extracellular fluid. It is the most abundant cation in the extracellular fluid. It is mostly in the form of sodium chloride. 95% of the sodium salt in the body is excreted by the kidney. The main function of sodium is to maintain the extracellular fluid volume, maintain the osmotic pressure and acid-base balance, and maintain the normal stress of muscle and nerve.