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Hyponatremia is a potentially serious condition in which the sodium level in the blood is too low. As a result, water moves into the body’s cells and causes them to swell.

There are different types of hyponatremia:

  • Euvolemic hyponatremia — water level increases, but sodium level stays the same
  • Hypervolemic hyponatremia — water and sodium levels increase, but the water gain is greater
  • Hypovolemic hyponatremia — water and sodium levels decrease, but the sodium loss is greater

Hyponatremia may be caused by:

  • Syndrome of inappropriate antidiuretic hormone secretion (SIADH) — The antidiuretic hormone is impaired and signals the kidneys to absorb more water, reducing urine output.
  • Sweating — In people with cystic fibrosis, excess sodium is excreted through sweat. It may also occur in people with severe burns when electrolytes and fluids are not replaced.
  • Some diuretics — Diuretics may increase sodium levels and impair your ability to filter them out of your body.

Risk Factors  

Factors that may increase your chance of hyponatremia include:

  • Advanced age
  • Excess water intake without electrolytes, which may occur when:
    • People are participating in endurance exercise
    • There is a lot of vomiting and/or diarrhea
    • Kidney failure
    • Heart failure
    • Cirrhosis
    • Hypothyroidism
    • Pancreatitis
    • Peritonitis
    • Treatment for uncontrolled diabetes
    • Certain types of cancer
    • Meningitis
    • Head injury
  • Certain medications, such as some diuretics or antipsychotics

Symptoms of Hyponatremia

People with mild hyponatremia usually don't have symptoms. As hyponatremia progresses, symptoms will appear and worsen.

Moderate to severe hyponatremia may cause:

  • Nausea
  • Loss of appetite
  • Irritability
  • Headache
  • Restlessness
  • Sluggishness
  • Confusion
  • Hallucinations
  • Muscle twitching

Severe and rapid onset hyponatremia may cause seizures, coma or death.

Diagnosis & Treatment 

Your doctor will ask about your symptoms and medical history and perform a physical exam. Your doctor may order a blood or urine test to check the sodium level in your blood and the functioning of your organs.

Treatment options may include:

  • Restricting your fluid intake
  • Identifying the underlying cause and getting proper treatment
  • Medications to help remove extra fluid from your body
  • IV fluids to help restore your body to a proper balance


Call 434.243.3675


Content was created using EBSCO’s Health Library. Edits to original content made by Rector and Visitors of the University of Virginia. This information is not a substitute for professional medical advice.

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