A condition that happens when the level of sodium in the blood is too low.

Sodium helps regulate the amount of water that's in and around cells. In hyponatremia, the level of sodium in the blood is too low. This causes the body's water level to rise, and cells begin to swell. This swelling can cause many health problems, from mild to life-threatening conditions.

Symptoms include nausea, headache, confusion and fatigue. In serious cases, seizures can occur.

Treatment is aimed at addressing the underlying cause, if possible. Limiting fluid intake and medicines to treat nausea and headaches can help. In more-serious cases, hospitalization for treatment to slowly raise the sodium levels in the blood may be needed.