CausesBy Mayo Clinic Staff
Sodium plays a key role in your body. It helps maintain normal blood pressure, supports the work of your nerves and muscles, and regulates your body's fluid balance.
A normal sodium level is between 135 and 145 milliequivalents per liter (mEq/L) of sodium. Hyponatremia occurs when the sodium in your blood falls below 135 mEq/L.
Many possible conditions and lifestyle factors can lead to hyponatremia, including:
May 28, 2014
- Certain medications. Some medications, such as some water pills (diuretics), antidepressants and pain medications, can cause you to urinate or perspire more than normal.
- Heart, kidney and liver problems. Congestive heart failure and certain diseases affecting the kidneys or liver can cause fluids to accumulate in your body, which dilutes the sodium in your body, lowering the overall level.
- Syndrome of inappropriate anti-diuretic hormone (SIADH). In this condition, high levels of the anti-diuretic hormone (ADH) are produced, causing your body to retain water instead of excreting it normally in your urine.
- Chronic, severe vomiting or diarrhea. This causes your body to lose fluids and electrolytes, such as sodium.
- Drinking too much water. Because you lose sodium through sweat, drinking too much water during endurance activities, such as marathons and triathlons, can dilute the sodium content of your blood. Drinking too much water at other times can also cause low sodium.
- Dehydration. Taking in too little fluid can also be a problem. If you get dehydrated, your body loses fluids and electrolytes.
- Hormonal changes. Adrenal gland insufficiency (Addison's disease) affects your adrenal glands' ability to produce hormones that help maintain your body's balance of sodium, potassium and water. Low levels of thyroid hormone also can cause a low blood-sodium level.
- The recreational drug Ecstasy. This amphetamine increases the risk of severe and even fatal cases of hyponatremia.
- Papadakis MA, ed., et al. Current Medical Diagnosis & Treatment 2014. 53rd ed. New York, N.Y.: The McGraw-Hill Companies; 2014. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=1. Accessed March 11, 2014.
- Spasovski G. Clinical practice guideline on diagnosis and treatment of hyponatraemia. Nephrology Dialysis Transplantation. 2014; 29(suppl):i1.
- Longo DL, et al. Harrison's Online. 18th ed. New York, N.Y.: The McGraw-Hill Companies; 2012. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=4. Accessed March 11, 2014.
- Hyponatremia. The Merck Manuals: The Merck Manual for Health Care Professionals. http://www.merckmanuals.com/professional/endocrine_and_metabolic_disorders/electrolyte_disorders/hyponatremia.html. Accessed March 14, 2014.
- Sodium, serum. Mayo Medical Laboratories. http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/81692. Accessed March 15, 2014.
- Sterns RH. Causes of hyponatremia in adults. http://www.uptodate.com/home. Accessed March 11, 2014.
- Bennett BL, et al. Wilderness medical society practice guidelines for treatment of exercise-associated hyponatremia. Wilderness & Environmental Medicine. 2013;24:228.