What is it?

Hyponatremia is a lower than normal concentration of sodium in the blood. Sodium is an electrolyte that helps with nerve and muscle function, and also helps to maintain blood pressure. May also be spelled hyponatraemia.

Who gets it?

Hyponatremia is more likely to occur in people whose kidneys do not function properly, as well as in those with heart failure, cirrhosis of the liver, and Addison?s disease, in which underactive adrenal glands excrete too much sodium.

What causes it?

Sodium must be maintained at a specific concentration in the blood and the fluid surrounding the body?s cells for the body to function properly. The body maintains a balance of sodium in the blood by matching the amount of sodium we take in with the amount excreted (put out) by the kidneys. Hyponatremia occurs when the level of sodium in the blood becomes diluted by too much water intake. This can be caused by kidney disorders in which the kidneys have difficulty eliminating fluids. It can also be caused by diuretic drugs used to treat high blood pressure. These drugs make the kidneys produce more urine, which can wash away too much sodium, especially when the patient is following a low sodium diet. Some psychiatric disorders cause people to drink extremely large quantities of water, which can result in hyonatremia. Other causes include receiving too much fluid intravenously, prolonged diarrhea or vomiting, marathon running, hypothalamus and pituitary disorders, certain types of cancer, and a combination of poor diet and excessive consumption of beer.

What are the symptoms?

Because the brain is very sensitive to sodium levels, low sodium causes symptoms including confusion and lethargy. The patient may feel nauseated, and experience muscle twitching, which can progress to seizures. Eventually, severe hyponatremia can lead to coma and death.

How is it diagnosed?

Hyponatremia is diagnosed by measuring the sodium levels in a blood sample. Normal blood sodium levels are 136 to 145 milliequivalents per liter (mEq/L) of blood. A patient with hyponatremia will have a blood sodium level lower than 136 mEq/L. Your doctor will also perform tests and study your medical history to look for the underlying cause of your condition.

What is the treatment?

Mild hyponatremia is treated by reducing your intake of water and monitoring the use of diuretics. When hyponatremia is severe, it is considered a medical emergency that is treated in a hospital. The doctor will slowly increase the blood sodium levels with intravenous (IV) fluids. Additional treatment depends upon the underlying cause of hyponatremia.

Self-care tips

If you take diuretics, make sure you have your blood sodium levels checked on a regular basis. If you are sick and symptoms include vomiting or diarrhea, follow your doctor?s recommendations for replacing lost fluids with clear liquids or electrolyte replacement fluids. People who run marathons and train intensely should drink electrolyte replacement fluids to keep sodium levels balanced.