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Low Blood Sodium (Hyponatremia)
Low blood sodium, or hyponatremia, occurs when water and sodium are out of balance in your body. It can cause weakness, headache, nausea, and m...

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What Does It Mean to Have Low Blood Sodium?

Insufficient sodium in your blood is also known as hyponatremia. Sodium is an essential electrolyte that helps maintain the balance of water in and around your cells. Sodium is important for proper muscle and nerve function. It also helps to maintain stable blood pressure levels.

Low blood sodium occurs when water and sodium are out of balance. In other words, there’s either too much water or not enough sodium.

Causes of Low Sodium in Blood

Many factors can cause low blood sodium. Sodium levels may get too low if your body is losing too much water and electrolytes. It may also be a symptom of certain medical conditions. Causes of low sodium include:

  • severe vomiting or diarrhea
  • taking certain medications, including antidepressants and pain medications
  • taking diuretics (water pills)
  • drinking too much water during exercise (this is very rare)
  • dehydration
  • kidney disease or failure
  • liver disease
  • heart problems
  • adrenal gland disorders, such as Addison’s disease
  • hypothyroidism (underactive thyroid)
  • primary polydipsia, a condition in which excess thirst makes you drink too much
  • using ecstasy
  • syndrome of inappropriate antidiuretic hormone (SIADH), which makes your body retain water
  • diabetes insipidus, a rare condition in which the body doesn’t make antidiuretic hormone 
  • Cushing syndrome, which causes high cortisol levels (this is rare)

Who Is at Risk for Low Sodium in Blood?

Certain factors increase your risk for low blood sodium, including:

  • old age
  • taking diuretics
  • taking antidepressants
  • being a high-performance athlete
  • living in a warmer climate
  • being on a low-sodium diet

If you’re at risk for low sodium, you may need to be more careful about your intake of electrolytes and water.

Symptoms of Low Sodium in Blood

Symptoms of low blood sodium can vary from person to person. If your sodium levels fall gradually, you may not experience any symptoms. If your sodium levels drop very quickly, symptoms may be more severe.

Losing sodium quickly is a medical emergency. It can cause loss of consciousness, seizures, and coma.

Common symptoms of low blood sodium include:

  • weakness
  • fatigue or low energy
  • headache
  • nausea and vomiting
  • muscle cramps or spasms
  • confusion
  • irritability

Tests for Low Sodium in Blood

A blood test can check for low sodium levels. Even if you’re not experiencing symptoms of low blood sodium, your doctor may order a basic metabolic panel. This tests the amounts of electrolytes and minerals in your blood. A basic metabolic panel is often part of a routine physical. It may identify low blood sodium in someone without any symptoms.

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

If blood sodium levels are low but urine levels are high, your body is losing too much sodium. Low sodium levels in both blood and urine mean your body is not taking in enough sodium. There may also be too much water in your body.

Treatment for Low Blood Sodium

Treatment for low blood sodium varies depending on the cause. It may include:

  • cutting back on fluid intake
  • adjusting the dosage of diuretics
  • medications for symptoms such as headaches, nausea, and seizures
  • treating underlying conditions
  • intravenous (IV) sodium solution infusion

Prevention of Low Blood Sodium

Keeping your water and electrolyte levels in balance can help prevent low blood sodium. If you are an athlete, it’s very important to drink the right amount of water during exercise. 

If you’re an athlete, you should also consider a drinking a rehydration beverage, such as Gatorade or Powerade. These drinks contain electrolytes, including sodium. They help replenish sodium lost through sweating. These drinks are also helpful if you lose a lot of fluids through vomiting or diarrhea.

During a typical day, women should aim to drink 2.2 liters of fluids per day. Men should aim for 3 liters. 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 breastfeeding
  • you’re vomiting
  • you have diarrhea
  • you have a fever

You should drink no more than 1 liter of water per hour. Don’t forget that it’s possible to drink too much water too quickly.

Written by: Janelle Martel
Edited by:
Medically Reviewed by: Steven Kim, MD
Published: Sep 26, 2015
Published By: Healthline Networks, Inc.
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