Low Blood Sodium (Hyponatremia)

Written by Janelle Martel | Published on July 2, 2012
Medically Reviewed by George Krucik, MD

What Does It Mean to Have Low Blood Sodium?

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

Low blood sodium occurs when water and sodium are out of balance. Either there is too much water or too little sodium.

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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 anti-depressants and pain medications
  • use of diuretics (water pills)
  • drinking too much water during exercise (although 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
  • use of ecstasy
  • syndrome of inappropriate anti-diuretic hormone (ADH), which makes your body retain water
  • diabetes insipidus, a rare condition in which the body doesn’t make ADH
  • Cushing syndrome, which causes high cortisol levels (rare)

Who Is at Risk for Low Sodium in Blood?

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

  • old age
  • using diuretics
  • being on anti-depressants
  • taking ecstasy
  • being a high-performance athlete
  • living in warmer climates
  • being on a low-sodium diet

If you are 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 unconsciousness, seizures, and coma.

Common low sodium symptoms include:

  • weakness
  • fatigue
  • headache
  • nausea and vomiting
  • muscle cramps
  • confusion
  • irritability

Tests for Low Sodium in Blood

A blood test can be used to check for low sodium levels. Even if you are 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. The amount of sodium in your urine will be checked. 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 headache, nausea, and seizures
  • treating underlying conditions
  • intravenous (IV) sodium solution

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 is very important to drink the right amount of water during exercise. You should drink no more than 1 liter per hour. Don’t forget that it is possible to drink too much water.

Athletes 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 are adequately hydrated, your urine will be pale yellow and you will not feel thirsty.

It is important to increase your fluid intake:

  • in warm weather
  • at high altitudes
  • when pregnant or breastfeeding
  • during intense exercise
  • during a fever
  • if you are vomiting or have diarrhea.
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