Hyponatremia: Symptoms, Causes, Treatment



To better understand and control the state of the body, it is important to know the levels of various nutrients in the blood. For example, to test your hydration you have to check your sodium levels.

Together with chlorine, sodium forms the product we all know as salt. Sodium plays an important role in the body’s water balance, in the regulation of blood pressure, and in the functioning of muscle and nerve cells. Hyponatremia is an abnormally low level of sodium in the blood. It is a fairly common disorder, especially in the elderly or those who take a lot of medication. It is usually discovered by chance when a blood test is taken.

What exactly is hyponatremia?

The first thing to know is that natremia is the level of sodium in the blood. Sodium is an electrolyte with the chemical formula Na+, involved in the process of regulating the amount of water in the body.

Hyponatremia is neither a symptom nor a disease; it’s a biological anomaly. It is defined by a decrease in the concentration of sodium in the blood, with a value below 135 mmol/l. Since natremia is the concentration of sodium in blood plasma, it means that the dilution of body fluids is too high. The normal level of natremia is between 135 and 145 mmol/l of plasma. It may be the result of excessive water intake or excessive loss of salt.


What causes hyponatremia?

  • Extremely high water consumption, especially during prolonged physical activity: Drinking too much water can lead to low sodium levels, as the kidneys’ ability to excrete water is exceeded. As sodium is lost through sweat, drinking too much water during endurance activities can dilute the sodium content of the blood;
  • Glucocorticoid deficiency and underactive thyroid (hypothyroidism);
  • Certain medications (antidepressants, diuretics, anti-epileptics, opioids, metoclopramide);
  • Diseases in which unusually large amounts of antidiuretic hormone (ADH) are released (lung cancer, brain damage and head trauma, tuberculosis, pneumonia…): high levels of antidiuretic hormone cause the body to retain water instead of excreting it normally in the urine;
  • Anorexia, psychosis;
  • Increased sodium loss through the digestive tract (profuse vomiting and/or severe diarrhea);
  • Extremely low sodium diet;
  • Liver cirrhosis and heart failure: heart failure and certain diseases that affect the kidneys or liver can cause fluid accumulation in the body, which dilutes the sodium, lowering its total level.

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