What are the symptoms of hyponatremia?

Hyponatremia refers to a serum sodium concentration below 135 mmol/L. Clinically, hyponatremia is classified into three severity grades: mild, moderate, and severe. It is relatively common in clinical practice—particularly among elderly patients—and its primary symptoms include generalized weakness, nausea and vomiting, headache, somnolence, muscle pain, cramps, neuralgia, and reversible ataxia.

What Are the Symptoms of Hyponatremia?

When hyponatremia develops within 48 hours (acute onset), it poses a significant risk: rapid progression to seizures, coma, respiratory arrest, or death may occur, potentially resulting in permanent neurological damage. Additionally, hyponatremia can cause cerebral edema and clinical manifestations of increased intracranial pressure.

Hyponatremia may result from inadequate sodium intake—for example, due to restrictive diets or fasting—or excessive sodium loss via vomiting, diarrhea, or extensive burns.

Certain medications—including diuretics and osmotic diuretics—can induce hyponatremia. Other causes include mineralocorticoid deficiency, tubulointerstitial kidney disease, and acute kidney injury with polyuria.

Hyponatremia may also arise secondary to glucocorticoid deficiency or hypothyroidism.

Treatment of hyponatremia involves both addressing the underlying cause and sodium replacement therapy. For acute hyponatremia, immediate sodium repletion is required. In chronic symptomatic cases, correction must proceed gradually, with serum sodium rising no faster than 1 mmol/(L·h). Hypovolemic hyponatremia is managed with isotonic saline infusion for volume expansion; adrenal insufficiency requires glucocorticoid replacement. In hypervolemic hyponatremia, loop diuretics are administered alongside strict restriction of oral fluid intake.

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