A low level of blood sodium is a sign that your body’s concentration of electrolytes has changed. This condition, which is called hyponatremia, can lead to several dangerous health problems. Early signs of low sodium levels are difficult to diagnose, but can progress to cause brain swelling, brain damage and possibly death when left untreated. Contact a health care provider immediately if you develop signs of hyponatremia.
When levels of sodium in your blood drop below 135 millimoles per liter you may begin to develop signs of hyponatremia, according to American Family Physician. The most common cause for hyponatremia is water retention brought on by either drinking excessive amounts of water or from conditions that prevent your kidneys from metabolizing water properly. A mild case of hyponatremia can cause bloating or make you feel nauseous. Your brain is especially sensitive to changes in sodium, so you may feel sluggish or confused, notes the Merck Manual. Because these symptoms are typical of many health problems, mild cases of hyponatremia are difficult to identify.
Severe hyponatremia causes water to enter your brain, which results in cerebral edema. This is dangerous because the build up of water makes your brain expand. Since space inside your skull is limited, pressure on your brain increases as it expands against the skull. When cerebral edema occurs slowly, your body has a chance to adapt and flush water out of your brain. You are in danger of brain damage when cerebral edema progresses quickly and your body does not have time to adapt before the pressure on your brain increases.
A rare form of brain damage called central pontine myelinolysis occurs when sodium levels increase too rapidly. This can pull water away from the brain, which damages the protective layer that covers nerves, called the myelin sheath. Symptoms of this condition appear a few days after treatment for hyponatremia and include impaired thinking, weakness in arms and legs, and difficulty with coordination. When the condition is severe, it can lead to coma and death. Liver transplant patients, burn victims and people with eating disorders or HIV-AIDS are most vulnerable. Many patients improve, but sometimes the nerve damage is long-lasting and not treatable.
Death can result from extreme cases of hyponatremia that progress quickly. This is more common with patients who are recovering from surgery or people who have certain health conditions, such as kidney, heart and liver failure. Patients who are waiting for liver transplants are at a much greater risk of dying when their blood sodium levels decrease to the point of hyponatremia and they begin to retain water, according to the "New England Journal of Medicine."