Sodium (Na)
Sodium is the most abundant electrolyte in blood and is critical for maintaining fluid balance, blood pressure, nerve impulse transmission, and muscle contraction. The kidneys tightly regulate sodium levels. Even small deviations from normal can cause significant symptoms, making sodium one of the most important blood parameters.
Reference Ranges
Male
136 – 145
mEq/L
Female
136 – 145
mEq/L
Child
136 – 145
mEq/L
Ages 1–18
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low sodium (hyponatremia) causes confusion, nausea, headache, fatigue, and in severe cases seizures or coma. Common causes include excess water intake, diuretics, heart failure, liver cirrhosis, kidney disease, and SIADH (syndrome of inappropriate ADH). It is the most common electrolyte abnormality in hospitalized patients.
What High Levels Mean
High sodium (hypernatremia) causes thirst, confusion, irritability, muscle twitching, and seizures. It almost always indicates dehydration (not excess salt intake). Common causes include inadequate water intake, diarrhea, diabetes insipidus, and fever. Elderly patients are particularly vulnerable.
Frequently Asked Questions
Can drinking too much water lower sodium?
Yes. Drinking excessive water without adequate electrolytes dilutes blood sodium — called dilutional hyponatremia. This is most commonly seen in marathon runners, psychiatric patients with compulsive water drinking, and people using ecstasy/MDMA. Severe cases can be life-threatening.
Does eating salt raise blood sodium?
In healthy people, the kidneys compensate by excreting excess salt, so dietary salt rarely raises blood sodium. Instead, excess salt raises blood pressure by causing water retention. High blood sodium is almost always caused by water loss, not salt excess.
What sodium level is dangerous?
Below 120 mEq/L is severe hyponatremia — risk of seizures and brain edema. Above 155 mEq/L is severe hypernatremia — risk of brain shrinkage and bleeding. Both extremes are medical emergencies requiring careful correction in a hospital setting.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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