Sodium

This article is a stub, meaning that it is unfinished. It will eventually be expanded.

Sodium is an abundant electrolyte in the body, and sodium ion (Na+) is the dominant ion in the extracellular space. 65% of sodium is in the extracellular space. The main clinical function of sodium is to maintain osmolality.

Abnormally low or high sodium (hyponatraemia and hypernatraemia, respectively), are common but potentially lethal disorders in the worst case.

Reference ranges

Parameter	Sample	Reference range
Sodium	Serum	136 – 146 mM
Osmolality	Serum	275 – 305 mOsmol/kg
Osmolality	Urine	50 – 1400 mOsmol/kg

Sodium in the body

70% of sodium in the body is free, not bound to any molecules.

The remaining 30% is not free but rather bound to large organic molecules in bone, cartilage, and connective tissue.

Sodium regulation

The level of sodium in the body is regulated by the renin-angiotensin-aldosterone system (RAAS) and by anti-diuretic hormone (ADH).

Sodium in the diet

Too much sodium in the diet increases the risk of cardiovascular disease. Most people today eat much more sodium than is recommended.

Sodium in laboratory medicine

When measuring sodium levels in a blood test, flame photometry or ion-selective electrodes (potentiometry) is used.