Hyponatremia is characterized by an abnormally low sodium level in the blood. Symptoms can vary, but may include weakness, fatigue, headaches, nausea, and more.

Sodium is an essential electrolyte that helps maintain water balance in and around the cells. It’s vital for proper muscle and nerve function. It also helps maintain stable blood pressure levels.

Insufficient sodium in the blood is known as hyponatremia. It occurs when the balance between water and sodium is disrupted. In other words, there’s either too much water or not enough sodium in your blood.

Read on to learn more about hyponatremia, including the symptoms and causes, treatment options, and more.

Symptoms of low blood sodium can vary from person to person. If your sodium levels fall gradually, you may not experience any symptoms initially, but they may eventually occur.

If sodium levels drop very quickly, your symptoms may be more evident and severe.

Possible symptoms of hyponatremia include:

Severe symptoms of hyponatremia

Losing sodium quickly is a medical emergency. It can cause:

  • overactive reflexes
  • loss of consciousness
  • seizures
  • coma
  • and in the most severe cases, death

If you or someone you know seems to be losing consciousness or is having a seizure, seek immediate medical help.

Sodium level should usually be between 135 and 145 milliequivalents per liter (mEq/L). Hyponatremia occurs when it falls below 135 mEq/L.

Many factors can cause hyponatremia. If the body loses too much water and electrolytes, sodium levels may get too low. Hyponatremia may also be a symptom of certain medical conditions.

Causes of hyponatremia include:

Certain factors increase the risk of hyponatremia, including:

  • older age
  • diuretic use
  • antidepressant use
  • being a high-performance athlete, such as a marathon runner
  • living in a warmer climate
  • having a condition such as:
    • heart failure
    • kidney disease
    • SIADH

If you’re at risk for low sodium levels, you may need to be more careful about your electrolytes and water intake. You may wish to talk with a healthcare professional about the risk factors and whether there are any steps you can take to lessen the risk.

Without treatment, hyponatremia can lead to serious complications, including:

  • osteoporosis
  • brain swelling
  • brain injury
  • seizures
  • death

If you are at a higher risk for hyponatremia due to preexisting conditions, it’s important to take any new symptoms seriously and talk with a doctor as quickly as possible.

A blood test can help your doctor check for low sodium levels.

Even if you don’t have symptoms of low blood sodium, your doctor may order a basic metabolic panel as part of a routine physical. This test measures the levels of electrolytes and minerals in your blood.

If the levels are abnormal, your doctor may then order a urine test to check the amount of sodium in the urine. The results of this test will help your doctor determine the cause of your low blood sodium:

  • If your blood sodium levels are low but your urine sodium levels are high, your body is losing too much sodium.
  • Low sodium levels in both your blood and your urine suggest either dehydration or volume overload.

To help confirm the diagnosis, your doctor may order a few other tests to check for hyponatremia, including:

  • liver function tests
  • a chest X-ray or computed tomography (CT) scan of your chest
  • CT scan of your head

Treatment for low blood sodium varies depending on factors including:

  • the cause
  • how severe the symptoms are,
  • how low the blood sodium levels are

Treatments for hyponatremia may include:

  • reducing fluid intake
  • adjusting the dosage of diuretics
  • taking medications for symptoms such as headaches, nausea, and seizures
  • treating underlying conditions
  • stopping or changing a medication for a chronic condition that may be negatively affecting blood sodium levels
  • an intravenous (IV) sodium solution

Keeping your water and electrolyte levels balanced can help prevent low blood sodium.

If you’re an athlete, it’s important to drink the right amount of water during exercise.

You may also want to consider drinking rehydration beverages. These drinks contain electrolytes and help replenish the sodium lost through sweating. They are also helpful if you lose a lot of fluids through vomiting or diarrhea.

Staying hydrated throughout the day can help manage any sudden fluctuations in blood sodium levels. When you’re adequately hydrated, your urine will be pale yellow or clear, and you won’t feel thirsty.

It’s important to increase your fluid intake if:

  • the weather is warm
  • you’re at a high altitude
  • you’re pregnant or nursing
  • you’re vomiting
  • you have diarrhea
  • you have a fever

Don’t forget that it’s possible to drink too much water too quickly. This is another reason to maintain good hydration throughout the day rather than drinking lots of water at once.

Hypernatremia is a condition that is closely related to hyponatremia.

What is hypernatremia?

While hyponatremia involves low sodium levels in the blood, hypernatremia occurs when there is too much sodium.

When people don’t get enough water, either because of limited access to water or an impaired thirst mechanism, they can develop hypernatremia. Less commonly, it’s caused by diabetes insipidus.

Hypernatremia occurs when your serum sodium level exceeds 145 milliequivalents per liter (Eq/L).

Hypernatremia can cause:

  • confusion
  • neuromuscular excitability
  • hyperreflexia
  • seizures
  • coma

Hyponatremia refers to too little sodium in your blood. It can be caused by a variety of factors, from excessive vomiting or diarrhea to conditions such as Addison’s disease.

A blood test and urine test can help diagnose hyponatremia. Treatments may include managing fluid intake, adjusting the dosage of diuretics, and treating any underlying cause.

Hyponatremia can be mild and cause no symptoms, or it can be very severe and life threatening. Seek immediate medical help if you or somebody else develops symptoms such as overactive reflexes, loss of consciousness, or seizures.