Hyponatremia: Symptoms, Causes & Treatment

Hyponatremia is a disorder in which the sodium concentration in the blood falls below the normal level. Sodium is an essential mineral that regulates the balance of water inside and outside cells and plays an important role in nerve and muscle function. It is among the most common salt disorders, especially in older adults and hospital patients.

In most cases hyponatremia is not the result of low intake but of an imbalance in water and sodium: it may result from excess water retention (as in heart, liver, or kidney failure, or the syndrome of inappropriate antidiuretic hormone), from sodium loss (such as diarrhea, severe vomiting, or excess diuretics), or from drinking huge amounts of water quickly. Symptoms depend on the severity and speed of onset: mild or slow deficiency may be symptomless, while a more severe or rapid drop causes nausea, headache, fatigue, confusion, and muscle cramps, and in severe cases may lead to brain swelling, seizures, and coma.

Diagnosing hyponatremia relies on a blood test, but most important is determining the cause because treatment differs accordingly. Correcting sodium is a delicate matter needing medical supervision: correcting it too quickly can itself be dangerous to the brain, so it is done carefully at a calculated rate. Treatment includes addressing the underlying cause (such as adjusting medications or treating the causative disease), fluid restriction in some types, or giving saline solutions in others. Any hyponatremia accompanied by symptoms, or that develops quickly, therefore needs urgent medical evaluation and is not self-corrected by excess salt.

• Nausea, headache, and fatigue.
• Confusion, difficulty concentrating, and behavior change.
• Muscle cramps and weakness.
• In severe cases: seizures, brain swelling, coma.

• Excess water retention (heart, liver, or kidney failure, excess antidiuretic hormone).
• Sodium loss (severe diarrhea and vomiting, excess diuretics).
• Drinking huge amounts of water quickly.
• Some medications and gland disorders.

• A blood sodium test.
• Tests to determine the cause (kidney and liver function, other salts, blood and urine osmolality).
• Clinical assessment of the body's fluid status.

Addressing the cause

• Treating the causative disease and adjusting medications like diuretics.

Correcting sodium carefully

• Fluid restriction in types linked to water retention.
• Saline solutions in other cases, at a calculated rate to avoid dangerous rapid correction.

Correction needs close medical supervision and is not done by oneself. This content is educational and does not replace medical advice.

• Brain swelling, seizures, and coma in severe or rapid cases.
• Risk of too-rapid correction to the brain (osmotic demyelination).
• Falls and injuries from confusion and weakness.

• Managing chronic diseases (heart, liver, kidney) and monitoring salts.
• Caution with diuretics and medications affecting sodium.
• Avoiding severe excess water intake quickly during long activities.