A low level of sodium in the blood is hyponatremia. Sodium is a mineral that helps keep the right amount of water in and around your cells. It is one of the most important minerals as well. It helps your body: Keep blood pressure normal Keep nerves and muscles working the right way Control the normal flow of nutrients between body fluids and cells Your doctor will work to find and treat any hidden cause. You may need to have drugs help raise the sodium in your blood. You may be in the hospital until your levels are back to normal.