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Hyponatremia—Adult

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

Definition

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

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:
- Kidney disease
- Certain medicine
- Syndrome of inappropriate antidiuretic hormone secretion —change in hormones that control water level in body

Normal Anatomy of the Kidney

Risk Factors

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:
- Kidney failure
- Heart failure
- Advanced liver disease— cirrhosis
- Underactive thyroid gland— hypothyroidism
- Inflammation of the pancreas— pancreatitis
- Inflammation of the abdominal lining— peritonitis
- Treatment for uncontrolled diabetes
- Certain types of cancer
- Meningitis
- Head injury
Having prostate surgery
Sweating in people without cystic fibrosis or severe burns

Symptoms

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:

Seizures
Coma
Death

Diagnosis

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

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

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

RESOURCES

American Society for Nutrition
http://www.nutrition.org

National Institute of Diabetes and Digestive and Kidney Diseases
http://www.niddk.nih.gov

CANADIAN RESOURCES

The College of Family Physicians of Canada
http://www.cfpc.ca

Health Canada
https://www.canada.ca

References

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.

Revision Information

Reviewer: EBSCO Medical Review Board Michael Woods, MD, FAAP
Review Date: 11/2018
Update Date: 12/03/2018

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This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.