Background Info:

Hyponatremia is a potentially life-threatening condition that occurs when there is too little sodium in the blood.

Defined as a blood sodium level below 135 mmol/L

Sign & Symptoms:

Early signs may include fatigue, headaches, confusion, and nausea.

If it is not quickly resolved, it can lead to seizures, coma, and death.


Can occur when excessive amounts of sodium are lost through urination, perspiration, vomiting, or diarrhea.

Health conditions or medications that cause fluid retention can cause dilutional hyponatremia, as can overhydration

Medical conditions that may lead to hyponatremia include congestive heart failure (CHF), kidney disease, and syndrome of inappropriate anti-diuretic hormone (SIADH).

Psychogenic polydipsia leads sufferers to drink excessive amounts of water and affects up to 1/5 of psychiatric patients and frequently leads to hyponatremia.

Affected Populations:

Overhydration leading to hyponatremia used to be more common among athletes, particularly women, who participated in long-duration sports such as marathons

  • Those who engage in endurance sports and those who treat athletes in distress are now better equipped to prevent, recognize, and manage hyponatremia thanks to a concerted effort int he sports medicine community to raise awareness about risks and signs of overhydration

Diuretics may deplete the body of electrolytes including sodium

SSRI antidepressants, such as paroxetine, which increase levels of antidiuretic hormone, have led to life-threatening cases of hyponatremia, especially in elderly patients

IV administration of hypotonic fluids, which contain a lower concentration of sodium than blood, in excessive quantities or speeds can cause dilutional hyponatremia

  • This occurs most commonly in children and the elderly

Patients receiving parenteral nutrition also need to be closely monitored, and their orders adjusted as needed, to maintain proper fluid and electrolyte balance


Avoiding dietary sodium is unlikely to cause hyponatremia. Even a very low-sodium diet of 500 to 1000 mg/day should maintain adequate levels under normal circumstances.

How to Diagnose:

The health care provider will perform a complete physical examination to help determine the cause of your symptoms. Blood and urine tests will be done.

Lab tests that can confirm and help diagnose low sodium include:

  • Comprehensive metabolic panel (includes blood sodium)
  • Osmolality blood test
  • Urine osmolality
  • Urine sodium


Fluids through a vein (IV)

Medication to relieve symptoms

Water restriction


Outcome depends on the condition that is causing the problem.

Low sodium that occurs in less than 48 hours (acute hyponatremia), is more dangerous than low sodium that develops slowly over time. When sodium level falls slowly over days or weeks (chronic hyponatremia), the brain cells have time to adjust and swelling may be minimal.

Possible Complications:

In severe cases, low sodium can lead to:

  • Decreased consciousness, hallucinations or coma
  • Brain herniation
  • Death




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