What it means
The main positive ion in the fluid outside the body's cells. Where sodium goes, water follows, so the serum sodium shows the balance of salt and water in the body. A low level is hyponatremiahy-poh-nuh-TREE-mee-uhA blood sodium level below normal, under 135 mEq/L.hypo- belownatr sodium (from its Latin name, natrium)-emia in the bloodFull entry ; a high level is hypernatremiahy-per-nuh-TREE-mee-uhA blood sodium level above normal, over 145 mEq/L.hyper- abovenatr sodium (from its Latin name, natrium)-emia in the bloodFull entry . Both mainly affect the brain, causing confusion, and at their worst seizures.
For the nurse
Watch for changes in mental status and report a value outside the normal range. Low-sodium diets limit salt for clients with heart failure, high blood pressure and kidney disease.
Remember it
Salt pulls water: where sodium goes, water goes.
At a glance
| Normal range | 135–145 mEq/L [135–145 mmol/L] |
|---|---|
| Critical range | Below 120 or above 160 mEq/L [below 120 or above 160 mmol/L]; each lab sets its own critical values. |
| Abbreviations | Na, Na+ (chemical symbol); NaCl (sodium chloride, salt) |
| Spanish | sodio |
| Also written | serum sodium, sodium level, sodium levels |
Related terms
potassium
A mineral in the blood that nerves and muscles, including the heart, need in order to work.
electrolyte
A mineral that carries an electric charge when dissolved in body fluids, such as sodium, potassium, calcium and chloride.
hyponatremia
A blood sodium level below normal, under 135 mEq/L.
hypernatremia
A blood sodium level above normal, over 145 mEq/L.