Having low sodium levels in the blood is called hyponatremia, and it can lead a number of serious health issues if not treated. Sodium is an electrolyte and it helps the nerves and muscles to function properly, as well as helps to maintain your blood pressure. The most important thing to keep in mind when it comes to hyponatremia is that there are other medical conditions that have the same or similar symptoms, so it's critical that you don't try and self-diagnose. Some symptoms of hyponatremia are lethargy, confusion, nausea, muscle twitching and even seizures.
If your kidneys are not able to properly eliminate fluids, then this can be one possible cause for the sodium levels in your blood to drop. Hyponatremia is likely to happen to those with improperly functioning kidneys.
Your adrenal gland secretes aldosterone, a hormone that it is necessary that your kidney have in order to hang onto enough sodium and not release it into your urine. If for some reason your adrenal gland malfunctions and doesn't release this hormone, your blood sodium levels can drop. Addison's disease is one condition that can affect your adrenal gland to prevent it from secreting aldosterone.
Your hypothalamus and pituitary gland also play a part when it comes to regulating the sodium in your blood stream. They make and secrete a hormone called vasopressin into your blood stream that is an anti-diuretic. This hormone causes the kidneys to reduce the amount of water into urine. If the body were to produce too much vasopressin, then it is possible that with the extra water, your blood sodium levels could go down.
Drinking really large amounts of water can cause hyponatremia, or low blood sodium levels. The extra water is absorbed into the bloodstream and dilutes the sodium. There are some psychiatric conditions that might cause a person to drink over 20 liters of water a day.
If you receive too many fluids intravenously, it is possible for the sodium levels to drop in your blood because more fluids are being absorbed into the bloodstream and diluting what sodium is there.
If you have prolonged and severe bouts of diarrhea, this can cause your sodium levels to drop. Diarrhea can cause up to 8 to 10 liters of fluid loss from the large intestines, and a lot of water and sodium and other nutrients can be lost with it.