Hyponatremia

(Low blood sodium)

What is hyponatremia?
Hyponatremia means that the sodium level in the blood is below normal. Your body needs sodium for fluid balance, blood pressure control, as well as the nerves and muscles. The normal blood sodium level is 135 to 145 milliequivalents/liter (mEq/L). Hyponatremia occurs when your blood sodium level goes below 135 mEq/L.

When the sodium level in your blood is too low, extra water goes into your cells and makes them swell. This swelling can be dangerous especially in the brain, since the brain cannot expand past the skull.

What causes hyponatremia?

A low sodium level in your blood may be caused by too much water or fluid in the body. This "watering down" effect makes the amount of sodium seem low. Low blood sodium can also be due to losing sodium from the body or losing both sodium and fluid from the body.

Hyponatremia can be the result of illnesses and medications. Some causes that may be related to kidney disease include:

  • Kidney failure - the kidneys cannot get rid of extra fluid from the body
  • Congestive heart failure - excess fluid builds up in the body
  • Diuretics (water pills) - makes the body get rid of more sodium in the urine
  • Antidepressants and pain medication - may cause more sweating or urinating than normal
  • Severe vomiting or diarrhea - the body loses a lot of fluid and sodium
  • Excessive thirst (primary polydipsia) - causes too much fluid intake

What are the symptoms of hyponatremia?
There may be no symptoms if you have mild hyponatremia. You may have symptoms when the level of sodium in your blood goes too low or drops too fast. In severe cases, you may have one or more of the following:

  • Nausea or vomiting.
  • Headache, confusion, or fatigue
  • Low blood pressure
  • Loss of energy
  • Muscle weakness, twitching, or cramps
  • Seizures or coma
  • Restlessness or bad temper

How do you treat hyponatremia?
Treatment is based on the cause and the seriousness of your hyponatremia. You may have to cut back on the amount of liquids you drink if you have extra water in your body. Your healthcare provider may also adjust your diuretic (water pill) use to raise the level of blood sodium. You may also need one or more of the following:

  • Intravenous (IV) fluid - Sodium solutions may be given through your vein to increase the amount of sodium in your blood. This is usually done in the hospital.
  • Sodium retaining medicines: These medicines help your kidneys get rid of large amounts of urine. This makes the extra water leave your body and keeps the sodium inside your body.
  • Dialysis: If your kidneys are not working well you may need to have dialysis to decrease the extra water in your body.

If you would like more information, please contact us.

© 2014 National Kidney Foundation. All rights reserved. This material does not constitute medical advice. It is intended for informational purposes only. Please consult a physician for specific treatment recommendations.