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What causes low sodium levels?

The short answer:

Sodium is one of the most important electrolytes in your body. The main causes of low sodium levels in your body include diseases such as liver cirrhosis, and kidney problems, hormonal changes, excessive water intake, and certain medications such as diuretics and antidepressants. Find more about the causes of low sodium levels in this article.

Key Facts:

  • The normal sodium blood levels range from 135-140 mmol/L.
  • The low sodium blood level is known as hyponatremia.
  • Hyponatremia means your sodium blood level is below 135 mmol/L.
  • The main causes of hyponatremia are the following:
    • Diseases (kidney diseases, liver cirrhosis, and heart failure).
    • Dehydration (loss of sodium due to diarrhea or vomiting).
    • Hormonal changes (hypothyroidism and adrenal gland insufficiency).
    • Excessive drinking of water.
    • Medications such as diuretics and antidepressants.
  • Symptoms of hyponatremia include nausea, vomiting, fatigue, and mental disorder in case of acute or severe hyponatremia.
  • Age, some medications, and certain diseases are among the most common risk factors for hyponatremia.

The main functions of sodium in your body.

What does a low sodium level mean?

Causes of low sodium levels

Symptoms of low sodium levels

Risk factors of low sodium levels

What are the main functions of sodium in your body?

The main functions of sodium electrolytes in your body are the following:

  • It helps in maintaining normal blood pressure.
  • Sodium supports the work of your nerves and muscles.
  • It regulates fluid balance within your body.

As the main function of sodium is to regulate water content inside the cells, when the sodium concentration decreases, water enters the cell leading to cell swelling. This condition could lead to health problems ranging from mild to life-threatening problems.

What does a low sodium level mean?

  • The normal blood sodium level range from 135 to 145 mmol/L.
  • The decreased blood concentration of sodium is commonly referred to as hyponatremia.
  • Hyponatremia means your serum sodium level is lower than 135 mmol/L It represents one of the most common electrolyte disorders in clinical medicine.
  • Hyponatremia affects about 10% of patients on hospitalized admission (Ref).

What are the main causes of low sodium levels?

The main causes of low sodium levels (Hyponatremia) are listed below


The most common diseases that cause a decrease in sodium blood levels are the following (Ref):

  • Liver cirrhosis
  • Diarrhea
  • Heart failure
  • Kidney problems
  • Pancreatitis
  • Peritonitis (abdominal cavity inflammation)
  • Intestinal blockage
  • Brain disorders such as head injury, bleeding, stroke, infection, and tumors
  • Severe burns

Hormonal changes

  • Adrenal gland insufficiency (Addison’s disease):

The adrenal gland is responsible for the production of hormones that regulate your body’s levels of sodium, potassium, and water. A decrease in the adrenal gland hormonal secretions leads to decreased sodium blood level.

  • Hypothyroidism:

Low levels of thyroid hormone also can cause a low blood sodium level.

The thyroid-stimulating hormone (TSH) determination is important during the evaluation of patients with low serum sodium levels.

  • The Syndrome of inappropriate antidiuretic hormone secretion (SIADH):

The main function of the antidiuretic hormone is to regulate water balance in the body by controlling water loss in the urine.

Increased secretion of antidiuretic hormone (ADH), causes your body to retain water and decrease its excretion in the kidney.

Increased water volume, dilute your sodium concentration leading to hyponatremia (Ref).

Excessive drinking of water

  • Most common among athletes in marathons. Drinking too much water could decrease the sodium concentration in your blood (make it more diluted when the volume of water is increased by excessive water intake).
  • Too much water could overwhelm the ability of kidneys to excrete water (Ref).


Dehydration may result from chronic, severe, vomiting and/or diarrhea causing excessive loss of body electrolytes including sodium.

Certain types of medications include the following:

  • Diuretics (most common)
  • Barbiturates
  • Carbamazepine
  • Chlorpropamide
  • Clofibrate
  • Opioids
  • Tolbutamide
  • Vincristine

What are the symptoms of low sodium levels (hyponatremia)?

Hyponatremia is claasifeod into into 3 categories.

  • Mild hyponatremia: the sodium blood levels range from 130-135 mmol/L
  • Moderate hyponatremia: the sodium blood levels range from 125-129 mmol/L
  • Profound hyponatremia: the sodium blood levels below 125 mmol/L

The symptoms of hyponatremia vary according to the blood sodium level.

Symptoms of mild hyponatremia:

  • Headache
  • Nausea
  • Fatigue

Symptoms of severe hyponatremia

  • Loss of energy and generalized fatigue
  • Muscle spasms and cramps
  • Restlessness
  • Confusion
  • Disorientation
  • Seizures
  • Coma
  • Respiratory arrest

Symptoms of chronic hyponatremia

Severe hyponatremia occurs through several days or weeks of low sodium blood levels.

Symptoms of chronic hyponatremia include the following

  • Nausea
  • Vomiting
  • Dizziness
  • Fatigue
  • Difficulty of walking
  • Being forgetful
  • Muscle spasms or cramps

What are the risk factors for low sodium blood levels?

The main risk factors for developing low blood sodium concentration include the following:


  • Elderly people are at higher risk of having low sodium blood levels compared with adults (Ref).
  • With age, many changes occur in body functions including alteration of kidney functions, also elderly commonly take medications higher than the younger. Some medications could lower the sodium blood level such as diuretics that are commonly used by the elderly to control blood pressure (Ref).

Medication history

  • Certain medications are commonly associated with a higher risk of developing low sodium blood concentration.
  • Thiazide diuretics and antidepressant agents are the most common medications reported to increase your risk of low sodium blood levels.

Certain diseases

  • Kidney diseases for example could affect the excretion of water from your body and thus could alter your sodium blood levels.
  • Other diseases such as diabetes Mellitus, liver cirrhosis, and heart failure.