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Hypernatremia (High Level of Sodium in the Blood)


James L. Lewis III

, MD, Brookwood Baptist Health and Saint Vincent’s Ascension Health, Birmingham

Last full review/revision Apr 2020| Content last modified Apr 2020

In hypernatremia, the level of sodium in blood is too high.

  • Hypernatremia involves dehydration, which can have many causes, including not drinking enough fluids, diarrhea, kidney dysfunction, and diuretics.
  • Mainly, people are thirsty, and if hypernatremia worsens, they may become confused or have muscle twitches and seizures.
  • Blood tests are done to measure the sodium level.
  • Usually, fluids are given intravenously to slowly reduce the sodium level in the blood.

(See also Overview of Electrolytes and Overview of Sodium's Role in the Body.)

Sodium is one of the body's electrolytes, which are minerals that carry an electric charge when dissolved in body fluids such as blood. In hypernatremia, the body contains too little water for the amount of sodium. The sodium level in the blood becomes abnormally high when water loss exceeds sodium loss.

Usually, hypernatremia results from dehydration. For example, people may lose body fluids and become dehydrated due to

  • Drinking too little
  • Vomiting
  • Having diarrhea
  • Using diuretics (drugs that increase urination)
  • Sweating excessively

Insufficient water intake usually plays an important role.

People with diabetes mellitus and high blood sugar levels may urinate excessive amounts, causing dehydration. Dehydration can also be caused by kidney disorders and by diabetes insipidus, which also causes people to urinate excessive amounts although without high blood sugar levels,and is due to inadequate or ineffective vasopressin secretion or action.

Rarely, adrenal gland disorders can cause mild hypernatremia without dehydration. Excessive administration of salt (usually in hospitalized people) is another rare cause of hypernatremia. Hypernatremia is most common among older people.

Symptoms of Hypernatremia

Hypernatremia typically causes thirst. The most serious symptoms of hypernatremia result from brain dysfunction. Severe hypernatremia can lead to confusion, muscle twitching, seizures, coma, and death.

Diagnosis of Hypernatremia

  • Measurement of sodium level in the blood

The diagnosis is based on blood tests indicating that the sodium level is high.

Doctors may do further testing to identify the cause of the hypernatremia, including measurements of urine volume and concentration. A special test called the water deprivation test is useful in identifying some causes, such as diabetes insipidus. The doctor monitors a person carefully during the 12-hour course of this test, because it is potentially dangerous.

Treatment of Hypernatremia

  • Fluid replacement

Hypernatremia is treated by replacing fluids. In all but the mildest cases, dilute fluids (containing water and a small amount of sodium in carefully adjusted concentrations) are given intravenously. The sodium level in blood is reduced slowly because reducing the level too rapidly can cause permanent brain damage.

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