Hyponatremia (HI-po-nuh-TREE-mee-uh) is an abnormally low level of sodium in the blood.
Sodium in the body is important for maintaining blood pressure and helping nerves and muscles work properly. It also regulates the amount of water in cells. When there's too little sodium outside the cells, water moves into the cells and causes them to swell, which is especially problematic in brain cells.
Hyponatremia can lead to a number of health problems and cause symptoms like nausea, vomiting, headache, confusion, and fatigue. Severe cases can lead to seizures and coma and can be life threatening.
Hyponatremia can be caused by heart, kidney, or liver problems, diarrhea, sweating, vomiting, dehydration, or certain drugs and medications. Since sodium is lost in sweat, hyponatremia also can be caused by drinking too much water during exercise, especially extended, intense exercise, such as a marathon or triathlon.
A sudden drop in sodium levels can be a medical emergency and should be treated right away. Cases of hyponatremia that develop over time are generally less serious and may cause no symptoms. Hyponatremia is a treatable condition as long as it's identified early.
All A to Z dictionary entries are regularly reviewed by KidsHealth medical experts.
