Hyponatremia is a potentially serious condition in which the level of sodium in the blood is too low. An imbalance is created when there is too little sodium for the amount of water in the body. As a result, water moves into the body’s cells causing them to swell.
There are different types of hyponatremia, each resulting in low sodium in the body: Euvolemic hyponatremia—water level increases, but sodium level stays the sameHypervolemic hyponatremia—water and sodium levels increase, but the water gain is greaterHypovolemic hyponatremia—water and sodium levels decrease, but the sodium loss is greater
Hyponatremia may be caused by: Syndrome of inappropriate antidiuretic hormone secretion
(SIADH)—Antidiuretic hormone signals the kidneys to absorb more water, reducing urine output. In SIADH, the mechanism that stops antidiuretic hormone from collecting water is impaired. This impairment results in excess water in the body.
Sweating—In people with
, excess sodium is excreted through sweat. It may also occur in people with severe
when electrolytes and fluids are not replaced.
Some diuretics—Increase sodium is lost in the urine.
Normal Anatomy of the Kidney
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Factors that may increase your chance of hyponatremia include: Advanced age
Excess water intake without electrolytes—may occur when:
People are participating in endurance exerciseThere is a lot of vomiting and/or diarrheaCertain medications, such as some diuretics or antipsychotics
Certain health conditions, such as:
Kidney failureHeart failure
Advanced liver disease—
Underactive thyroid gland—
Inflammation of the pancreas—
Inflammation of the abdominal lining—
peritonitisTreatment for uncontrolled diabetesCertain types of cancerMeningitisHead injuryHaving prostate surgerySweating in people without cystic fibrosis or severe burns
People with mild hyponatremia usually don't have symptoms. As hyponatremia progresses, symptoms will appear and worsen.
Moderate to severe hyponatremia may cause: NauseaLoss of appetiteIrritabilityHeadacheRestlessnessSluggishnessConfusionHallucinationsMuscle twitching
Severe and rapid onset hyponatremia may cause
, or death.
Your doctor will ask about your symptoms and medical history. A physical exam will be done. Your doctor will ask you about your fluid intake and do some tests.
Tests may include: Blood tests—to check the sodium level in your blood, and the functioning of your organsUrine test—to check the sodium level in your urine
Other tests may be done to look for any underlying causes of your hyponatremia.
Treatment may depend on: What is causing the low sodium levelHow long the sodium level has been lowHow low the sodium level isYour level of hydration
In cases when the sodium has been low for more than 1-2 days, your doctor will want to correct the sodium level slowly. Serious complications may occur when sodium levels rise too rapidly. It can be corrected more quickly if it has been lw for a short time.
Treatment options may include: Restricting fluid intakeIdentifying the underlying cause and getting proper treatmentMedications to help remove extra fluid from your bodyIV fluids to deliver sodium restore proper balance
To help reduce your chance of hyponatremia: If participating in sports, drink only as much water as you need to quench your thirst. Sport drinks that provide electrolytes, such as sodium, along with water may be helpful during endurance events.Work with your doctor to effectively manage any conditions that you may have.
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Syndrome of inappropriate antidiuretic hormone secretion (SIADH). EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated December 15, 2012. Accessed November 15, 2013.
Last reviewed December 2014 by Michael Woods, MD
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.
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