Sodium
Sodium is the main electrolyte outside cells. It controls fluid balance, nerve transmission, and muscle contraction. Both low (hyponatraemia) and high (hypernatraemia) sodium can cause neurological symptoms and, when severe, are medical emergencies.
Normal Range
135–145 mmol/L
Reference ranges may vary slightly between laboratories. Always interpret your result in context with your doctor.
Why is Na+ measured?
Sodium is part of the basic metabolic panel. It is tested in any acute illness, when symptoms suggest electrolyte disturbance (confusion, weakness, seizures), and to monitor patients on diuretics or fluid therapy.
High Na+ means…
High sodium (>145) almost always reflects water loss (dehydration) rather than salt excess. Causes include inadequate fluid intake, severe diarrhoea, fever, diabetes insipidus.
Low Na+ means…
Low sodium (<135) is the most common electrolyte disturbance in hospitalised patients. Causes include heart failure, liver disease, kidney problems, SIADH, certain drugs (especially SSRIs and thiazides), and excessive water intake.
Symptoms associated with abnormal Na+
When Na+ is high:
- Intense thirst
- Confusion
- Muscle twitching or seizures
- Lethargy
When Na+ is low:
- Headache, nausea
- Confusion, drowsiness
- Muscle cramps
- Seizures (severe cases)
- Coma (severe acute hyponatraemia)
How to improve your Na+
- Mild hyponatraemia in elderly people on SSRIs is common; medication review is often the answer.
- Severe rapid sodium changes (acute hyponatraemia in marathon runners, for example) require urgent evaluation.
- Do not correct chronic hyponatraemia too quickly — risk of central pontine myelinolysis.
Frequently asked questions about Na+
Why is salt restriction not the fix for low sodium?
Hyponatraemia is usually a relative water excess, not a salt deficit. Salt loading rarely helps and may worsen heart failure or hypertension. The primary intervention is fluid restriction or treating the underlying cause.
Medical Sources
This page is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider about your individual results.