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(Dilutional Hyponatremia; Euvolemic Hyponatremia; Hypervolemic Hyponatremia; Hypovolemic Hyponatremia)

Pronounced: hahy-po-nuh-TREE-mee-uh



Hyponatremia is the low level of sodium in the blood. Sodium helps to control fluid levels in the body. It also affects blood pressure, your muscles, and nerves. Low sodium can lead to mild to severe health problems.


Causes    TOP

The amount of sodium in your blood is most often affected by:

  • Change in the amount of fluid in the body.
    • Salt can leave the body through sweat, vomit and diarrhea. If you have lost a lot of fluid, you may also lose a lot of sodium.
    • Drinking too much water can dilute sodium in the blood.
  • Changes in the kidneys that allow more sodium to leave the blood than it should. Could be caused by:

Normal Anatomy of the Kidney

Kidney failure stones

Copyright © Nucleus Medical Media, Inc.


Risk Factors    TOP

Hyponatremia is more common in older adults. Other factors that may increase your chance of hyponatremia include:

  • Drinking very high amounts of water without electrolytes. Most common with:
    • People are participating in endurance exercise
    • There is a lot of vomiting and/or diarrhea
  • Certain medicine, such as some diuretics or antipsychotics
  • Certain health conditions, such as:
  • Having prostate surgery
  • Sweating in people without cystic fibrosis or severe burns

Symptoms    TOP

Mild changes will not cause symptoms.

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:


Diagnosis    TOP

You will be asked about your symptoms and past health. An exam will be done.

Tests may include:

  • Blood tests—to check the sodium level in your blood
  • Urine test—to see how much sodium is leaving the body

Treatment    TOP

Treatment may depend on:

  • What is causing the low sodium level
  • How long the sodium level has been low
  • How low the sodium level is
  • How much fluid is in your body

Care will be given in a hospital. The sodium level may need to be brought up slowly. Treatment options may include:

  • Limiting how much you drink—if sodium is normal but there is too much fluid
  • IV fluids—help balance sodium and fluid levels
  • Sodium pills
  • Medicine—to help balance fluid without losing more sodium

Your care team will help to find the cause. A plan will be made to avoid future problems. This may include better fluid options or changing medicine.


Prevention    TOP

During activity, drink only as much water as you need to meet your thirst. Long or intense activity may need drinks with electrolytes.


American Society for Nutrition

National Institute of Diabetes and Digestive and Kidney Diseases


The College of Family Physicians of Canada

Health Canada


Elhassan EA, Schrier RW. Hyponatremia: Diagnosis, complications, and management including V2 receptor antagonists (vaptans). Curr Opin Nephrol Hypertens. 2011;20(2):161-168.

Hyponatremia. EBSCO DynaMed Plus website. Available at: http://www.dynamed.com/topics/dmp~AN~T113706/Hyponatremia . Updated January 20, 2016. Accessed December 18, 2017.

Mittal R, Sheftel H, et al. Management of hyponatraemia. Br J Hosp Med (Lond). 2011;72(2):M22-5.

Syndrome of inappropriate antidiuresis (SIAD). EBSCO DynaMed website. Available at: http://www.dynamed.com/topics/dmp~AN~T115360/Syndrome-of-inappropriate-antidiuresis-SIAD . Updated August 4, 2016. Accessed December 18, 2017.

Last reviewed November 2018 by EBSCO Medical Review Board Michael Woods, MD, FAAP
Last Updated: 12/3/2018

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