Hyponatremia occurs when sodium levels in the blood are too low. Symptoms include lethargy, confusion, and fatigue. It can result from underlying conditions, such as kidney failure, or other factors, such as drinking too much water or taking certain medications.

Sodium is an electrolyte that plays an essential role in regulating the levels of water and other substances in the body. The definition of a low sodium level is below 135 milliequivalents per liter (mEq/L).

As the condition worsens, people may experience symptoms, such as:

  • vomiting
  • muscle twitches
  • seizures

Severe hyponatremia occurs when levels drop below 125 mEq/L. Health issues arising from extremely low sodium levels may be fatal.

Hyponatremia is the most common electrolyte disorder that doctors encounter. Research suggests that approximately 1.7 percent of people in the United States have the condition. It is more prevalent among people with cancer.


Tired and fatigues businessman in back of tax or car rubbing bridge of nose under glasses because of stress and exhaustion
Hyponatremia can cause fatigue and headaches.

Mild hyponatremia may not cause symptoms. When symptoms occur they include:

  • confusion
  • sluggishness
  • a headache
  • fatigue and low energy
  • nausea
  • restlessness

If the condition worsens, it can cause severe symptoms, particularly in older adults. Severe symptoms may include:

  • vomiting
  • muscle weakness, spasms, and twitching
  • seizures
  • coma

Hyponatremia can result in death in extreme cases.

What are the causes?

Other medical conditions and factors that can cause sodium levels to fall include:

  • diarrhea or vomiting
  • heart failure
  • kidney disease
  • liver disease
  • medication use
  • syndrome of inappropriate ADH secretion (SIADH)

People with SIADH produce excessive levels of the anti-diuretic hormone (ADH), which can lower sodium levels

Other causes include:

  • Drinking too much water.
  • Drug use. Taking the recreational drug ecstasy increases the risk of severe hyponatremia in some cases. Hyponatremia from ecstasy use can be fatal, especially in females.
  • Hormone disorders. These include Addison’s disease, which reduces the body’s production of the hormones cortisol and aldosterone and hypothyroidism, which is characterized by low levels of thyroid hormone.

Risk factors

Some medications may increase the risk of hyponatremia.
Some medications may increase the risk of hyponatremia.

Certain factors increase the risk of developing hyponatremia, including:

  • age
  • having specific conditions, such as SIADH or kidney, heart, or liver disease
  • taking certain diuretics, antidepressants, or pain medications
  • taking ecstasy
  • drinking excessive amounts of water
  • intense exercise, which may cause people to drink lots of water quickly

Diagnosis and when to see a doctor

People who are at risk of hyponatremia or develop symptoms should see their doctor right away as they may need urgent medical treatment.

People with symptoms including vomiting, seizures, or loss of consciousness require immediate attention. They should call an ambulance or go to the nearest emergency department.

To diagnose low sodium levels, a doctor will take a medical history, perform a physical examination, and order a blood test.

If the blood test shows low sodium levels, the doctor will typically need to perform additional tests to determine the cause.


Treatment for hyponatremia involves:

Restoring blood sodium levels

Those who have mild to moderate hyponatremia resulting from lifestyle factors or medication may be able to increase sodium to normal levels by:

  • drinking less fluids (often less than 1 quart per day)
  • adjusting medication dose or switching medications

Individuals with severe symptoms often require hospitalization and an intravenous (IV) sodium treatment to get their sodium levels back to normal. They may also require drugs to treat seizures or other hyponatremia symptoms.

Treating the underlying cause

Where the underlying cause of hyponatremia is a medical condition or hormonal disorder, people will usually need further treatment.

For example, people with liver, kidney, or heart problems may receive medications or surgery. Kidney problems often require dialysis, and people with liver or heart conditions may need a transplant.

People with a thyroid disorder can typically manage their symptoms and prevent hyponatremia and other complications with medications and lifestyle changes.

SIADH usually requires ongoing treatment to prevent hyponatremia. Individuals with the condition may need to restrict fluid intake, take salt tablets, or use medications.


Athlete drinking sports energy drink after exercising.
Sports drinks containing electrolytes can help prevent low blood sodium levels after intense exercise.

To avoid low blood sodium levels:

  • avoid drinking excessive amounts of water
  • consume sports drinks during intense exercise
  • do not take ecstasy
  • seek treatment for medical conditions
  • discuss medication use with a doctor
  • seek medical care if vomiting or diarrhea persist


The outlook for people with low sodium levels depends on the severity of the condition and the underlying cause.

Acute hyponatremia, which develops quickly, is more severe than chronic cases, which have a longer onset time. In severe cases, hyponatremia can be fatal.

To improve their outlook, people should be aware of the symptoms of hyponatremia and seek prompt medical attention if they experience any of them. Those at risk of low sodium levels should be especially vigilant.