Health Library

Hyponatremia—Adult

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

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

Definition

Hyponatremia is a condition in which the level of sodium in the blood is too low. This occurs when there is an imbalance in the amount of water and sodium in the body—too little sodium for the amount of water present. As a result, water moves into the body’s cells causing them to swell. This condition may be serious. It requires care from your doctor.

There are different types of hyponatremia, each resulting in low sodium in the body:

Type	What Happens?
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

Causes

Causes of hyponatremia include:

Too much fluid intake

Diarrhea or vomiting
Sweating
Conditions such as:
- Kidney failure
- Heart failure
- Cirrhosis (a type of liver damage)
- Hypothyroidism (underactive thyroid)
- Pancreatitis (inflammation of the pancreas)
- Peritonitis (inflammation of the abdominal lining)
- Blockage of small intestine
- Gland disorders (eg, Addison’s disease, syndrome of inappropriate secretion of antidiuretic hormone)
- Cancer
Taking certain medicines such as:
- Diuretics (medicines that increase urine output)
- Certain psychiatric medicines

Kidney Failure

Kidney failure is one condition that may cause hyponatremia.

Risk Factors

Risk factors include:

Drinking too much fluid (eg, water)

Taking certain medicines
Having certain conditions
Having certain medical procedures (eg, prostate surgery)
Participating in endurance exercise, like running marathons
Being of advanced age
IV treatment—While in the hospital, fluids may be delivered through a needle in the vein. In some cases, this may lead to hyponatremia.

Symptoms

With mild hyponatremia, you may have no symptoms at all. During more severe cases, symptoms may include:

Seizures
Unresponsiveness
Coma

If left untreated, the condition may lead to death.

Diagnosis

Your doctor will:

Ask about your symptoms
Ask about your fluid intake
Take your medical history
Do a physical exam

Tests may include:

Blood tests—to check the sodium level in your blood, as well as other blood tests to check the functioning of your organs (eg, kidneys, heart, liver)
Urine test—to check the sodium level in your urine

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

In most cases, your doctor will want to correct the sodium level slowly. Serious complications may occur when sodium levels rise too rapidly. Treatment options include:

Restricting the amount of fluids consumed
Identifying the underlying cause and getting proper treatment
Taking medicines to help remove extra fluid from your body
Using an IV to deliver sodium and fluid to correct the balance

Prevention

To help reduce your chance of getting hyponatremia, take these steps:

If participating in sports, drink only as much water or sports drinks as you need to quench your thirst. Sports drinks that provide electrolytes, such as sodium, may be helpful during endurance events.
Work with your doctor to effectively manage any conditions that you may have.

American Academy of Family Physicians

http://www.aafp.org/

National Institute of Diabetes and Digestive and Kidney Diseases

http://www2.niddk.nih.gov/

The College of Family Physicians of Canada

http://www.cfpc.ca/

Health Canada

http://www.hc-sc.gc.ca/

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Hyponatremia. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/. Updated July 3, 2011. Accessed August 22, 2011.

Hyponatremia. The Merck Manual for Healthcare Professionals website. Available at: http://www.merckmanuals.com/professional/sec13/ch167/ch167a.html. Updated May 2009. Accessed August 22, 2011.

Mayo Clinic Staff. Hyponatremia. Mayo Clinic website. Available at: http://www.mayoclinic.com/health/hyponatremia/DS00974. Updated July 14, 2011. Accessed August 22, 2011.

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

Peng K. Management of hyponatremia. Am Fam Physician. 2004;69(10):2387-2394.

Sodium. The Merck Manual Home Health Handbook for Patients and Caregivers website. Available at: http://www.merckmanuals.com/home/sec14/ch171/ch171b.html#v1151161. Updated August 2008. Accessed August 22, 2011.

Last reviewed September 2011 by Lawrence Frisch, MD, MPH

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.