MSD Manual

Please confirm that you are not located inside the Russian Federation

honeypot link

Hypernatremia (High Level of Sodium in the Blood)


James L. Lewis III

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

Reviewed/Revised Sep 2023

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 taking 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.

Sodium is one of the body's electrolytes, which are minerals Overview of Minerals Minerals are necessary for the normal functioning of the body’s cells. The body needs relatively large quantities of Calcium Chloride Magnesium read more 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 Overview of Sodium's Role in the Body Sodium is one of the body's electrolytes, which are minerals that the body needs in relatively large amounts. Electrolytes carry an electric charge when dissolved in body fluids such as blood... read more . The sodium level in the blood becomes abnormally high when water loss exceeds sodium loss.

  • Drinking too little

  • Vomiting

  • Having diarrhea

  • Using diuretics (medications that increase urination)

  • Sweating excessively

Insufficient water intake usually plays an important role. To maintain water balance, healthy adults should consume at least 6 glasses (about 1½ quarts, or 2 liters) of fluid a day. Total fluid intake includes drinking water or other beverages, as well as eating foods with a high water content, such as fruits, vegetables, and soup. Drinking too much is usually better than drinking too little, because excreting excess water is much easier for the body than conserving water. It is possible to drink too much but, for a healthy adult, the volume of fluid intake would have to be extreme (such as over 20 liters/day). When the kidneys are functioning normally, the body can handle wide variations in fluid intake.

Did You Know...

  • Healthy adults should consume at least 6 glasses (about 1½ quarts, or 2 liters) of fluid a day (including fluid from eating foods high in water content, such as fruits and vegetables).

Rarely, adrenal gland disorders Overview of the Adrenal Glands The body has 2 adrenal glands, one near the top of each kidney. They are endocrine glands, which secrete hormones into the bloodstream. Each adrenal gland has 2 parts. Medulla: The inner part... read more 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 adults.

Symptoms of Hypernatremia

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 Diagnosis Argininevasopressin deficiency (central diabetes insipidus) is a lack of the hormone vasopressin (antidiuretic hormone) that causes excessive production of very dilute urine (polyuria). Argininevasopressin... read more is useful in identifying some causes, such as argininevasopressin resistance. 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.

quiz link

Test your knowledge

Take a Quiz!