Hyponatremia
(Low Sodium)

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Medical Author:

Benjamin Wedro, MD, FACEP, FAAEM

Benjamin Wedro, MD, FACEP, FAAEM

Dr. Ben Wedro practices emergency medicine at Gundersen Clinic, a regional trauma center in La Crosse, Wisconsin. His background includes undergraduate and medical studies at the University of Alberta, a Family Practice internship at Queen's University in Kingston, Ontario and residency training in Emergency Medicine at the University of Oklahoma Health Sciences Center.

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Medical Editor:

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, Chief Medical Editor

Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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• Hyponatremia (Low Sodium) Overview
• Hyponatremia Causes
• Hyponatremia Symptoms
• When to Seek Medical Care
• Exams and Tests
• Hyponatremia Treatment
• Self Care at Home
• Medical Treatment
• Next Steps
• Follow-up
• Prevention
• Outlook
• Synonyms and Keywords
• Author and Editor
• Viewer Comments: Hyponatremia - Causes

Hyponatremia (Low Sodium) Overview

Sodium and water levels in the body are tightly regulated to keep it functioning normally. Sodium concentration is higher in the bloodstream than inside cells. Regulatory mechanisms help control and maintain sodium levels. The hormones aldosterone (made in the adrenal gland) and anti-diuretic hormone (ADH) or vasopressin (made in the pituitary) adjust the way the kidneys deal with water and sodium to maintain the appropriate total amount of sodium and water in the body.

Water in the body is closely linked to the location of sodium in the body. If the concentration of sodium is too high in the bloodstream, water will leak from cells into the blood stream to try to dilute and lower the sodium concentration. Conversely, if sodium levels in the bloodstream are too low, water will leave the blood and enter cells, causing them to swell.

Hyponatremia is the term used to describe low sodium levels in the bloodstream (hypo=low + natr=sodium + emia=blood). Acute hyponatremia describes the situation in which sodium levels drop quickly, while chronic hyponatremia describes situations with a gradual fall in the sodium concentrations over days or weeks. Chronic hyponatremia is often well tolerated since the body has a chance to adapt.

Neurologic changes are the most concerning consequence of hyponatremia. Cerebral edema (excess fluid in the brain, leading to swelling) may occur with severe or acute hyponatremia. Water enters the brain cells causing them to swell. Because the brain is enclosed in a bony skull that cannot expand, the brain is compressed since there is no room for swelling to occur. As a result, brain function may be compromised significantly.